* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Peter Zijlstra @ 2024-04-17 5:24 UTC (permalink / raw)
To: Elizabeth Figura
Cc: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Andy Lutomirski, linux-doc,
linux-kselftest, Randy Dunlap, Ingo Molnar, Will Deacon,
Waiman Long, Boqun Feng
In-Reply-To: <4340072.ejJDZkT8p0@terabithia>
On Tue, Apr 16, 2024 at 04:18:24PM -0500, Elizabeth Figura wrote:
> Is the concern about poor performance when ntsync is in use, or is nesting a
> lot of spinlocks like that something that could cause problems for unrelated
> tasks? I'm not familiar enough with the scheduler to know if this can be
> abused.
The problem is keeping preemption disabled for potentially a fairly long
time. By doing that you potentially affect the performance of other tasks.
^ permalink raw reply
* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Peter Zijlstra @ 2024-04-17 5:22 UTC (permalink / raw)
To: Elizabeth Figura
Cc: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Andy Lutomirski, linux-doc,
linux-kselftest, Randy Dunlap, Ingo Molnar, Will Deacon,
Waiman Long, Boqun Feng
In-Reply-To: <2602449.Lt9SDvczpP@terabithia>
On Tue, Apr 16, 2024 at 04:18:19PM -0500, Elizabeth Figura wrote:
> Let me know if that's good enough or if I should try to render it into plain
> text somehow.
Plain text is much preferred. I'm more of a text editor kinda guy --
being a programmer and all that.
>
>
^ permalink raw reply
* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Peter Zijlstra @ 2024-04-17 5:21 UTC (permalink / raw)
To: Elizabeth Figura
Cc: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Andy Lutomirski, linux-doc,
linux-kselftest, Randy Dunlap, Ingo Molnar, Will Deacon,
Waiman Long, Boqun Feng
In-Reply-To: <23472492.6Emhk5qWAg@terabithia>
On Tue, Apr 16, 2024 at 04:18:17PM -0500, Elizabeth Figura wrote:
> Over different lists. I don't know if there's a better way to name things to
> make that clearer.
D'oh, reading hard. I'll stare more.
^ permalink raw reply
* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Elizabeth Figura @ 2024-04-16 22:18 UTC (permalink / raw)
To: Peter Zijlstra, wine-devel
Cc: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Andy Lutomirski, linux-doc, linux-kselftest,
Randy Dunlap, Ingo Molnar, Will Deacon, Waiman Long, Boqun Feng,
Elizabeth Figura
In-Reply-To: <4340072.ejJDZkT8p0@terabithia>
On Tuesday, 16 April 2024 16:18:24 CDT Elizabeth Figura wrote:
> On Tuesday, 16 April 2024 03:14:21 CDT Peter Zijlstra wrote:
> > I don't support GE has it in his builds? Last time I tried, building
> > Wine was a bit of a pain.
>
> It doesn't seem so. I tried to build a GE-compatible ntsync build, uploaded
> here (thanks Arek for hosting):
>
> https://f002.backblazeb2.com/file/wine-ntsync/ntsync-wine.tar.xz
Oops, the initial version I uploaded had broken paths. Should be fixed now.
(It's also broken on an unpatched kernel unless explicitly disabled with
WINE_DISABLE_FAST_SYNC=1. Not sure what I messed up there—it should fall back
cleanly—but hopefully shouldn't be too important for testing.)
^ permalink raw reply
* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Elizabeth Figura @ 2024-04-16 21:18 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Andy Lutomirski, linux-doc,
linux-kselftest, Randy Dunlap, Ingo Molnar, Will Deacon,
Waiman Long, Boqun Feng
In-Reply-To: <20240416081421.GB31647@noisy.programming.kicks-ass.net>
On Tuesday, 16 April 2024 03:14:21 CDT Peter Zijlstra wrote:
> On Mon, Apr 15, 2024 at 08:08:10PM -0500, Elizabeth Figura wrote:
> > This patch series implements a new char misc driver, /dev/ntsync, which is
> > used to implement Windows NT synchronization primitives.
>
> This patch series does not apply to anything I have at hand. Nor does it
> state anything explicit to put it on top of.
It was written to apply against the 'char-misc-next' branch of gregkh/char-
misc.git. I'll make a note of that next time, sorry for the inconvenience.
> > Hence I would like to request review from someone familiar with locking to
> > make sure that the usage of low-level kernel primitives is correct and
> > that the wait queues work as intended, and to that end I've CC'd the
> > locking maintainers.
> I am sadly very limited atm, but I'll try and read through it. If only I
> could apply...
>
> > == Patches ==
> >
> > The intended semantics of the patches are broadly intended to match those
> > of the corresponding Windows functions. For those not already familiar
> > with the Windows functions (or their undocumented behaviour), patch 27/27
> > provides a detailed specification, and individual patches also include a
> > brief description of the API they are implementing.
> >
> > The patches making use of this driver in Wine can be retrieved or browsed
here:
> > https://repo.or.cz/wine/zf.git/shortlog/refs/heads/ntsync5
>
> I don't support GE has it in his builds? Last time I tried, building
> Wine was a bit of a pain.
It doesn't seem so. I tried to build a GE-compatible ntsync build, uploaded
here (thanks Arek for hosting):
https://f002.backblazeb2.com/file/wine-ntsync/ntsync-wine.tar.xz
> > Some aspects of the implementation may deserve particular comment:
> >
> > * In the interest of performance, each object is governed only by a single
> >
> > spinlock. However, NTSYNC_IOC_WAIT_ALL requires that the state of
> > multiple
> > objects be changed as a single atomic operation. In order to achieve
> > this, we first take a device-wide lock ("wait_all_lock") any time we
> > are going to lock more than one object at a time.
> >
> > The maximum number of objects that can be used in a vectored wait, and
> > therefore the maximum that can be locked simultaneously, is 64. This
> > number is NT's own limit.
> >
> > The acquisition of multiple spinlocks will degrade performance. This is
> > a
> > conscious choice, however. Wait-for-all is known to be a very rare
> > operation in practice, especially with counts that approach the
> > maximum, and it is the intent of the ntsync driver to optimize
> > wait-for-any at the expense of wait-for-all as much as possible.
>
> Per the example of percpu-rwsem, it would be possible to create a
> mutex-spinlock hybrid scheme, where single locks are spinlocks while
> held, but can block when the global thing is pending. And the global
> lock is always mutex like.
>
> If all that is worth it, I don't know. Nesting 64 spinlocks doesn't give
> me warm and fuzzy feelings though.
Is the concern about poor performance when ntsync is in use, or is nesting a
lot of spinlocks like that something that could cause problems for unrelated
tasks? I'm not familiar enough with the scheduler to know if this can be
abused.
I think we don't care about performance problems within Wine, at least. FWIW,
the scheme here is actually similar to what Windows does (as described by one
of their kernel engineers), although slightly different. NT nests spinlocks as
well, but instead of using the outer lock like our "wait_all_lock" to prevent
lock inversion, they instead sort the inner locks (by address, I assume).
If there's deeper problems... I can look into (ab)using a rwlock for this
purpose, at least for now.
In any case making wait_all_lock into a sleeping mutex instead of a spinlock
should be fine. I'll rerun performance tests but I don't expect it to cause
any problems.
^ permalink raw reply
* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Elizabeth Figura @ 2024-04-16 21:18 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Andy Lutomirski, linux-doc,
linux-kselftest, Randy Dunlap, Ingo Molnar, Will Deacon,
Waiman Long, Boqun Feng
In-Reply-To: <20240416160553.GA30707@noisy.programming.kicks-ass.net>
On Tuesday, 16 April 2024 11:05:53 CDT Peter Zijlstra wrote:
> On Mon, Apr 15, 2024 at 08:08:10PM -0500, Elizabeth Figura wrote:
> > The intended semantics of the patches are broadly intended to match those
> > of the corresponding Windows functions. For those not already familiar
> > with the Windows functions (or their undocumented behaviour), patch 27/27
> > provides a detailed specification, and individual patches also include a
> > brief description of the API they are implementing.
>
> You happen to have a readable copy of patch 27 around? RST is utter
> garbage to read :/
An HTML copy should be available here now (thanks Arek):
https://ivyl.gg/ntsync/ntsync.html
Let me know if that's good enough or if I should try to render it into plain
text somehow.
^ permalink raw reply
* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Elizabeth Figura @ 2024-04-16 21:18 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Andy Lutomirski, linux-doc,
linux-kselftest, Randy Dunlap, Ingo Molnar, Will Deacon,
Waiman Long, Boqun Feng
In-Reply-To: <20240416161917.GD12673@noisy.programming.kicks-ass.net>
On Tuesday, 16 April 2024 11:19:17 CDT Peter Zijlstra wrote:
> On Tue, Apr 16, 2024 at 05:53:45PM +0200, Peter Zijlstra wrote:
> > On Tue, Apr 16, 2024 at 05:50:14PM +0200, Peter Zijlstra wrote:
> > > On Tue, Apr 16, 2024 at 10:14:21AM +0200, Peter Zijlstra wrote:
> > > > > Some aspects of the implementation may deserve particular comment:
> > > > >
> > > > > * In the interest of performance, each object is governed only by a
> > > > > single
> > > > >
> > > > > spinlock. However, NTSYNC_IOC_WAIT_ALL requires that the state of
> > > > > multiple
> > > > > objects be changed as a single atomic operation. In order to
> > > > > achieve this, we first take a device-wide lock ("wait_all_lock")
> > > > > any time we are going to lock more than one object at a time.
> > > > >
> > > > > The maximum number of objects that can be used in a vectored wait,
> > > > > and
> > > > > therefore the maximum that can be locked simultaneously, is 64.
> > > > > This number is NT's own limit.
> > >
> > > AFAICT:
> > > spin_lock(&dev->wait_all_lock);
> > >
> > > list_for_each_entry(entry, &obj->all_waiters, node)
> > >
> > > for (i=0; i<count; i++)
> > >
> > > spin_lock_nest_lock(q->entries[i].obj->lock,
> > > &dev->wait_all_lock);
> > >
> > > Where @count <= NTSYNC_MAX_WAIT_COUNT.
> > >
> > > So while this nests at most 65 spinlocks, there is no actual bound on
> > > the amount of nested lock sections in total. That is, all_waiters list
> > > can be grown without limits.
> > >
> > > Can we pretty please make wait_all_lock a mutex ?
That should be fine, at least.
> > Hurmph, it's worse, you do that list walk while holding some obj->lock
> > spinlokc too. Still need to figure out how all that works....
>
> So the point of having that other lock around is so that things like:
>
> try_wake_all_obj(dev, sem)
> try_wake_any_sem(sem)
>
> are done under the same lock?
The point of having the other lock around is that try_wake_all() needs to lock
multiple objects at the same time. It's a way of avoiding lock inversion.
Consider task A does a wait-for-all on objects X, Y, Z. Then task B signals Y,
so we do try_wake_all_obj() on Y, which does try_wake_all() on A's queue
entry; that needs to check X and Z and consume the state of all three objects
atomically. Another task could be trying to signal Z at the same time and
could hit a task waiting on Z, Y, X, and that causes inversion.
The simple and easy way to implement everything is just to have a global lock
on the whole device, but this is kind of known to be a performance bottleneck
(this was NT's BKL, and they ditched it starting with Vista or 7 or
something).
Instead we use a lock per object, and normally in the wait-for-any case we
only ever need to grab one lock at a time, but when we need to do a wait-for-
all we need to lock multiple objects at once, and we grab the outer lock to
avoid potential lock inversion.
> Where I seem to note that both those functions do that same list
> iteration.
Over different lists. I don't know if there's a better way to name things to
make that clearer.
There's the "any" wait queue, which tasks which do a wait-for-any add
themselves to, and the "all" wait queue, which tasks that do a wait-for-all
add themselves to. Signaling an object could potentially wake up either one,
but checking whether a task is eligible is a different process.
^ permalink raw reply
* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Peter Zijlstra @ 2024-04-16 16:19 UTC (permalink / raw)
To: Elizabeth Figura
Cc: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Andy Lutomirski, linux-doc,
linux-kselftest, Randy Dunlap, Ingo Molnar, Will Deacon,
Waiman Long, Boqun Feng
In-Reply-To: <20240416155345.GC12673@noisy.programming.kicks-ass.net>
On Tue, Apr 16, 2024 at 05:53:45PM +0200, Peter Zijlstra wrote:
> On Tue, Apr 16, 2024 at 05:50:14PM +0200, Peter Zijlstra wrote:
> > On Tue, Apr 16, 2024 at 10:14:21AM +0200, Peter Zijlstra wrote:
> >
> > > > Some aspects of the implementation may deserve particular comment:
> > > >
> > > > * In the interest of performance, each object is governed only by a single
> > > > spinlock. However, NTSYNC_IOC_WAIT_ALL requires that the state of multiple
> > > > objects be changed as a single atomic operation. In order to achieve this, we
> > > > first take a device-wide lock ("wait_all_lock") any time we are going to lock
> > > > more than one object at a time.
> > > >
> > > > The maximum number of objects that can be used in a vectored wait, and
> > > > therefore the maximum that can be locked simultaneously, is 64. This number is
> > > > NT's own limit.
> >
> > AFAICT:
> >
> > spin_lock(&dev->wait_all_lock);
> > list_for_each_entry(entry, &obj->all_waiters, node)
> > for (i=0; i<count; i++)
> > spin_lock_nest_lock(q->entries[i].obj->lock, &dev->wait_all_lock);
> >
> > Where @count <= NTSYNC_MAX_WAIT_COUNT.
> >
> > So while this nests at most 65 spinlocks, there is no actual bound on
> > the amount of nested lock sections in total. That is, all_waiters list
> > can be grown without limits.
> >
> > Can we pretty please make wait_all_lock a mutex ?
>
> Hurmph, it's worse, you do that list walk while holding some obj->lock
> spinlokc too. Still need to figure out how all that works....
So the point of having that other lock around is so that things like:
try_wake_all_obj(dev, sem)
try_wake_any_sem(sem)
are done under the same lock?
Where I seem to note that both those functions do that same list
iteration.
Can't you write things like:
static void try_wake_all_obj(struct nysync_device *dev,
struct ntsync_obj *obj,
void (*wake_obj)(struct ntsync_obj *obj))
{
list_for_each_entry(entry, &obj->all_waiters, node) {
spin_lock(&obj->lock);
try_wake_all(dev, event->q, obj);
wake_obj(obj);
spin_unlock(&obj->lock);
}
}
And then instead of the above, write:
try_wake_all_obj(dev, sem, wake_sem);
[[ Also, should not something like try_wake_any_sem -- wake_sem in the
above -- have something like:
WARN_ON_ONCE(sem->type != NTSYNC_TYPE_SEM);
]]
^ permalink raw reply
* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Peter Zijlstra @ 2024-04-16 16:05 UTC (permalink / raw)
To: Elizabeth Figura
Cc: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Andy Lutomirski, linux-doc,
linux-kselftest, Randy Dunlap, Ingo Molnar, Will Deacon,
Waiman Long, Boqun Feng
In-Reply-To: <20240416010837.333694-1-zfigura@codeweavers.com>
On Mon, Apr 15, 2024 at 08:08:10PM -0500, Elizabeth Figura wrote:
> The intended semantics of the patches are broadly intended to match those of the
> corresponding Windows functions. For those not already familiar with the Windows
> functions (or their undocumented behaviour), patch 27/27 provides a detailed
> specification, and individual patches also include a brief description of the
> API they are implementing.
You happen to have a readable copy of patch 27 around? RST is utter
garbage to read :/
^ permalink raw reply
* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Peter Zijlstra @ 2024-04-16 15:53 UTC (permalink / raw)
To: Elizabeth Figura
Cc: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Andy Lutomirski, linux-doc,
linux-kselftest, Randy Dunlap, Ingo Molnar, Will Deacon,
Waiman Long, Boqun Feng
In-Reply-To: <20240416155014.GB12673@noisy.programming.kicks-ass.net>
On Tue, Apr 16, 2024 at 05:50:14PM +0200, Peter Zijlstra wrote:
> On Tue, Apr 16, 2024 at 10:14:21AM +0200, Peter Zijlstra wrote:
>
> > > Some aspects of the implementation may deserve particular comment:
> > >
> > > * In the interest of performance, each object is governed only by a single
> > > spinlock. However, NTSYNC_IOC_WAIT_ALL requires that the state of multiple
> > > objects be changed as a single atomic operation. In order to achieve this, we
> > > first take a device-wide lock ("wait_all_lock") any time we are going to lock
> > > more than one object at a time.
> > >
> > > The maximum number of objects that can be used in a vectored wait, and
> > > therefore the maximum that can be locked simultaneously, is 64. This number is
> > > NT's own limit.
>
> AFAICT:
>
> spin_lock(&dev->wait_all_lock);
> list_for_each_entry(entry, &obj->all_waiters, node)
> for (i=0; i<count; i++)
> spin_lock_nest_lock(q->entries[i].obj->lock, &dev->wait_all_lock);
>
> Where @count <= NTSYNC_MAX_WAIT_COUNT.
>
> So while this nests at most 65 spinlocks, there is no actual bound on
> the amount of nested lock sections in total. That is, all_waiters list
> can be grown without limits.
>
> Can we pretty please make wait_all_lock a mutex ?
Hurmph, it's worse, you do that list walk while holding some obj->lock
spinlokc too. Still need to figure out how all that works....
^ permalink raw reply
* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Peter Zijlstra @ 2024-04-16 15:50 UTC (permalink / raw)
To: Elizabeth Figura
Cc: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Andy Lutomirski, linux-doc,
linux-kselftest, Randy Dunlap, Ingo Molnar, Will Deacon,
Waiman Long, Boqun Feng
In-Reply-To: <20240416081421.GB31647@noisy.programming.kicks-ass.net>
On Tue, Apr 16, 2024 at 10:14:21AM +0200, Peter Zijlstra wrote:
> > Some aspects of the implementation may deserve particular comment:
> >
> > * In the interest of performance, each object is governed only by a single
> > spinlock. However, NTSYNC_IOC_WAIT_ALL requires that the state of multiple
> > objects be changed as a single atomic operation. In order to achieve this, we
> > first take a device-wide lock ("wait_all_lock") any time we are going to lock
> > more than one object at a time.
> >
> > The maximum number of objects that can be used in a vectored wait, and
> > therefore the maximum that can be locked simultaneously, is 64. This number is
> > NT's own limit.
AFAICT:
spin_lock(&dev->wait_all_lock);
list_for_each_entry(entry, &obj->all_waiters, node)
for (i=0; i<count; i++)
spin_lock_nest_lock(q->entries[i].obj->lock, &dev->wait_all_lock);
Where @count <= NTSYNC_MAX_WAIT_COUNT.
So while this nests at most 65 spinlocks, there is no actual bound on
the amount of nested lock sections in total. That is, all_waiters list
can be grown without limits.
Can we pretty please make wait_all_lock a mutex ?
> > The acquisition of multiple spinlocks will degrade performance. This is a
> > conscious choice, however. Wait-for-all is known to be a very rare operation
> > in practice, especially with counts that approach the maximum, and it is the
> > intent of the ntsync driver to optimize wait-for-any at the expense of
> > wait-for-all as much as possible.
Typical sane usage is a good guide for performance, but you must not
forget about malicious userspace and what they can do on purpose to mess
you up.
Anyway, let me stare more at all this....
^ permalink raw reply
* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Greg Kroah-Hartman @ 2024-04-16 8:49 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Elizabeth Figura, Arnd Bergmann, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Andy Lutomirski, linux-doc,
linux-kselftest, Randy Dunlap, Ingo Molnar, Will Deacon,
Waiman Long, Boqun Feng
In-Reply-To: <20240416081421.GB31647@noisy.programming.kicks-ass.net>
On Tue, Apr 16, 2024 at 10:14:21AM +0200, Peter Zijlstra wrote:
> On Mon, Apr 15, 2024 at 08:08:10PM -0500, Elizabeth Figura wrote:
> > This patch series implements a new char misc driver, /dev/ntsync, which is used
> > to implement Windows NT synchronization primitives.
>
> This patch series does not apply to anything I have at hand. Nor does it
> state anything explicit to put it on top of.
Should work on linux-next as I took a few of the original commits from
the last series already.
thanks,
greg k-h
^ permalink raw reply
* Re: [PATCH v7] posix-timers: add clock_compare system call
From: Sagi Maimon @ 2024-04-16 8:39 UTC (permalink / raw)
To: Mahesh Bandewar (महेश बंडेवार)
Cc: Thomas Gleixner, richardcochran, luto, mingo, bp, dave.hansen,
x86, hpa, arnd, geert, peterz, hannes, sohil.mehta,
rick.p.edgecombe, nphamcs, palmer, keescook, legion, mark.rutland,
mszeredi, casey, reibax, davem, brauner, linux-kernel, linux-api,
linux-arch, netdev
In-Reply-To: <CAF2d9jg0X_HKSZbiwPTEXdmrhY49D1zfT3Q4xzNAqv1z+TYXtA@mail.gmail.com>
Thanks
On Mon, Apr 15, 2024 at 8:23 PM Mahesh Bandewar (महेश बंडेवार)
<maheshb@google.com> wrote:
>
> On Sun, Apr 14, 2024 at 5:22 AM Sagi Maimon <maimon.sagi@gmail.com> wrote:
> >
> > On Thu, Apr 11, 2024 at 7:34 PM Mahesh Bandewar (महेश बंडेवार)
> > <maheshb@google.com> wrote:
> > >
> > > On Thu, Apr 11, 2024 at 12:11 AM Sagi Maimon <maimon.sagi@gmail.com> wrote:
> > > >
> > > > Hi Mahesh
> > > > What is the status of your patch?
> > > > if your patch is upstreamed , then it will have all I need.
> > > > But, If not , I will upstream my patch.
> > > > BR,
> > > >
> > > Hi Sagi,
> > >
> > > If you want to pursue the syscall option, then those are tangential
> > > and please go ahead. (I cannot stop you!)
> > > I'm interested in getting the "tight sandwich timestamps" that
> > > gettimex64() ioctl offers and I would want enhancements to
> > > gettimex64() done the way it was discussed in the later half of this
> > > thread. If you want to sign-up for that please let me know.
> > Hi Mahesh
> > I do need to modify the PTP_SYS_OFFSET_EXTENDED ioctl for cases which
> > gettimex64
> > not supported by the driver (look at Thomas suggestion), but I need
> > your changes in ptp_read_system_prets.
> > I like to add my changes above your changes, so we won't do duplicate work.
> > please show me your latest patch and the status of it
> > Once you have upstream yours , I will add my changes on the next patch.
>
> OK, in that case let me post the patch since your changes would need
> pieces from it.
>
> thanks,
> --mahesh..
>
> > BR
> > Sagi
> >
> > >
> > > thanks,
> > > --mahesh..
> > >
> > >
> > > > On Thu, Apr 11, 2024 at 5:56 AM Mahesh Bandewar (महेश बंडेवार)
> > > > <maheshb@google.com> wrote:
> > > > >
> > > > > On Wed, Apr 3, 2024 at 6:48 AM Thomas Gleixner <tglx@linutronix.de> wrote:
> > > > > >
> > > > > > On Tue, Apr 02 2024 at 16:37, Mahesh Bandewar (महेश बंडेवार) wrote:
> > > > > > > On Tue, Apr 2, 2024 at 3:37 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> > > > > > > The modification that you have proposed (in a couple of posts back)
> > > > > > > would work but it's still not ideal since the pre/post ts are not
> > > > > > > close enough as they are currently (properly implemented!)
> > > > > > > gettimex64() would have. The only way to do that would be to have
> > > > > > > another ioctl as I have proposed which is a superset of current
> > > > > > > gettimex64 and pre-post collection is the closest possible.
> > > > > >
> > > > > > Errm. What I posted as sketch _is_ using gettimex64() with the extra
> > > > > > twist of the flag vs. a clockid (which is an implementation detail) and
> > > > > > the difference that I carry the information in ptp_system_timestamp
> > > > > > instead of needing a new argument clockid to all existing callbacks
> > > > > > because the modification to ptp_read_prets() and postts() will just be
> > > > > > sufficient, no?
> > > > > >
> > > > > OK, that makes sense.
> > > > >
> > > > > > For the case where the driver does not provide gettimex64() then the
> > > > > > extension of the original offset ioctl is still providing a better
> > > > > > mechanism than the proposed syscall.
> > > > > >
> > > > > > I also clearly said that all drivers should be converted over to
> > > > > > gettimex64().
> > > > > >
> > > > > I agree. Honestly that should have been mandatory and
> > > > > ptp_register_clock() should fail otherwise! Probably should have been
> > > > > part of gettimex64 implementation :(
> > > > >
> > > > > I don't think we can do anything other than just hoping all driver
> > > > > implementations include gettimex64 implementation.
> > > > >
> > > > > > > Having said that, the 'flag' modification proposal is a good backup
> > > > > > > for the drivers that don't have good implementation (close enough but
> > > > > > > not ideal). Also, you don't need a new ioctl-op. So if we really want
> > > > > > > precision, I believe, we need a new ioctl op (with supporting
> > > > > > > implementation similar to the mlx4 code above). but we want to save
> > > > > > > the new ioctl-op and have less precision then proposed modification
> > > > > > > would work fine.
> > > > > >
> > > > > > I disagree. The existing gettimex64() is good enough if the driver
> > > > > > implements it correctly today. If not then those drivers need to be
> > > > > > fixed independent of this.
> > > > > >
> > > > > > So assumed that a driver does:
> > > > > >
> > > > > > gettimex64()
> > > > > > ptp_prets(sts);
> > > > > > read_clock();
> > > > > > ptp_postts(sts);
> > > > > >
> > > > > > today then having:
> > > > > >
> > > > > > static inline void ptp_read_system_prets(struct ptp_system_timestamp *sts)
> > > > > > {
> > > > > > if (sts) {
> > > > > > if (sts->flags & PTP_SYS_OFFSET_MONO_RAW)
> > > > > > ktime_get_raw_ts64(&sts->pre_ts);
> > > > > > else
> > > > > > ktime_get_real_ts64(&sts->pre_ts);
> > > > > > }
> > > > > > }
> > > > > >
> > > > > > static inline void ptp_read_system_postts(struct ptp_system_timestamp *sts)
> > > > > > {
> > > > > > if (sts) {
> > > > > > if (sts->flags & PTP_SYS_OFFSET_MONO_RAW)
> > > > > > ktime_get_raw_ts64(&sts->post_ts);
> > > > > > else
> > > > > > ktime_get_real_ts64(&sts->post_ts);
> > > > > > }
> > > > > > }
> > > > > >
> > > > > > or
> > > > > >
> > > > > > static inline void ptp_read_system_prets(struct ptp_system_timestamp *sts)
> > > > > > {
> > > > > > if (sts) {
> > > > > > switch (sts->clockid) {
> > > > > > case CLOCK_MONOTONIC_RAW:
> > > > > > time_get_raw_ts64(&sts->pre_ts);
> > > > > > break;
> > > > > > case CLOCK_REALTIME:
> > > > > > ktime_get_real_ts64(&sts->pre_ts);
> > > > > > break;
> > > > > > }
> > > > > > }
> > > > > > }
> > > > > >
> > > > > > static inline void ptp_read_system_postts(struct ptp_system_timestamp *sts)
> > > > > > {
> > > > > > if (sts) {
> > > > > > switch (sts->clockid) {
> > > > > > case CLOCK_MONOTONIC_RAW:
> > > > > > time_get_raw_ts64(&sts->post_ts);
> > > > > > break;
> > > > > > case CLOCK_REALTIME:
> > > > > > ktime_get_real_ts64(&sts->post_ts);
> > > > > > break;
> > > > > > }
> > > > > > }
> > > > > > }
> > > > > >
> > > > > > is doing the exact same thing as your proposal but without touching any
> > > > > > driver which implements gettimex64() correctly at all.
> > > > > >
> > > > > I see. Yes, this makes sense.
> > > > >
> > > > > > While your proposal requires to touch every single driver for no reason,
> > > > > > no?
> > > > > >
> > > > > > It is just an implementation detail whether you use a flag or a
> > > > > > clockid. You can carry the clockid for the clocks which actually can be
> > > > > > read in that context in a reserved field of PTP_SYS_OFFSET_EXTENDED:
> > > > > >
> > > > > > struct ptp_sys_offset_extended {
> > > > > > unsigned int n_samples; /* Desired number of measurements. */
> > > > > > clockid_t clockid;
> > > > > > unsigned int rsv[2]; /* Reserved for future use. */
> > > > > > };
> > > > > >
> > > > > > and in the IOCTL:
> > > > > >
> > > > > > if (extoff->clockid != CLOCK_MONOTONIC_RAW)
> > > > > > return -EINVAL;
> > > > > >
> > > > > > sts.clockid = extoff->clockid;
> > > > > >
> > > > > > and it all just works, no?
> > > > > >
> > > > > Yes, this should work. However, I didn't check if struct
> > > > > ptp_system_timestamp is used in some other context.
> > > > >
> > > > > > I have no problem to decide that PTP_SYS_OFFSET will not get this
> > > > > > treatment and the drivers have to be converted over to
> > > > > > PTP_SYS_OFFSET_EXTENDED.
> > > > > >
> > > > > > But adding yet another callback just to carry a clockid as argument is a
> > > > > > more than pointless exercise as I demonstrated.
> > > > > >
> > > > > Agreed. As I said, I thought we cannot change the gettimex64() without
> > > > > breaking the compatibility but the fact that CLOCK_REALTIME is "0"
> > > > > works well for the backward compatibility case.
> > > > >
> > > > > I can spin up an updated patch/series that updates gettimex64
> > > > > implementation instead of adding a new ioctl-op If you all agree.
> > > > >
> > > > > thanks,
> > > > > --mahesh..
> > > > >
> > > > > > Thanks,
> > > > > >
> > > > > > tglx
^ permalink raw reply
* Re: [PATCH v4 00/30] NT synchronization primitive driver
From: Peter Zijlstra @ 2024-04-16 8:14 UTC (permalink / raw)
To: Elizabeth Figura
Cc: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan,
linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Andy Lutomirski, linux-doc,
linux-kselftest, Randy Dunlap, Ingo Molnar, Will Deacon,
Waiman Long, Boqun Feng
In-Reply-To: <20240416010837.333694-1-zfigura@codeweavers.com>
On Mon, Apr 15, 2024 at 08:08:10PM -0500, Elizabeth Figura wrote:
> This patch series implements a new char misc driver, /dev/ntsync, which is used
> to implement Windows NT synchronization primitives.
This patch series does not apply to anything I have at hand. Nor does it
state anything explicit to put it on top of.
> Hence I would like to request review from someone familiar with locking to make
> sure that the usage of low-level kernel primitives is correct and that the wait
> queues work as intended, and to that end I've CC'd the locking maintainers.
I am sadly very limited atm, but I'll try and read through it. If only I
could apply...
> == Patches ==
>
> The intended semantics of the patches are broadly intended to match those of the
> corresponding Windows functions. For those not already familiar with the Windows
> functions (or their undocumented behaviour), patch 27/27 provides a detailed
> specification, and individual patches also include a brief description of the
> API they are implementing.
>
> The patches making use of this driver in Wine can be retrieved or browsed here:
>
> https://repo.or.cz/wine/zf.git/shortlog/refs/heads/ntsync5
I don't support GE has it in his builds? Last time I tried, building
Wine was a bit of a pain.
> Some aspects of the implementation may deserve particular comment:
>
> * In the interest of performance, each object is governed only by a single
> spinlock. However, NTSYNC_IOC_WAIT_ALL requires that the state of multiple
> objects be changed as a single atomic operation. In order to achieve this, we
> first take a device-wide lock ("wait_all_lock") any time we are going to lock
> more than one object at a time.
>
> The maximum number of objects that can be used in a vectored wait, and
> therefore the maximum that can be locked simultaneously, is 64. This number is
> NT's own limit.
>
> The acquisition of multiple spinlocks will degrade performance. This is a
> conscious choice, however. Wait-for-all is known to be a very rare operation
> in practice, especially with counts that approach the maximum, and it is the
> intent of the ntsync driver to optimize wait-for-any at the expense of
> wait-for-all as much as possible.
Per the example of percpu-rwsem, it would be possible to create a
mutex-spinlock hybrid scheme, where single locks are spinlocks while
held, but can block when the global thing is pending. And the global
lock is always mutex like.
If all that is worth it, I don't know. Nesting 64 spinlocks doesn't give
me warm and fuzzy feelings though.
^ permalink raw reply
* Re: [PATCH v4 27/27] docs: ntsync: Add documentation for the ntsync uAPI.
From: Randy Dunlap @ 2024-04-16 2:13 UTC (permalink / raw)
To: Elizabeth Figura, Arnd Bergmann, Greg Kroah-Hartman,
Jonathan Corbet, Shuah Khan
Cc: linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Peter Zijlstra, Andy Lutomirski,
linux-doc, linux-kselftest, Ingo Molnar, Will Deacon, Waiman Long,
Boqun Feng, Bagas Sanjaya
In-Reply-To: <20240416010837.333694-28-zfigura@codeweavers.com>
On 4/15/24 6:08 PM, Elizabeth Figura wrote:
> Add an overall explanation of the driver architecture, and complete and precise
> specification for its intended behaviour.
>
> Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
> Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Thanks.
> ---
> Documentation/userspace-api/index.rst | 1 +
> Documentation/userspace-api/ntsync.rst | 399 +++++++++++++++++++++++++
> 2 files changed, 400 insertions(+)
> create mode 100644 Documentation/userspace-api/ntsync.rst
--
#Randy
https://people.kernel.org/tglx/notes-about-netiquette
https://subspace.kernel.org/etiquette.html
^ permalink raw reply
* [PATCH v4 27/27] docs: ntsync: Add documentation for the ntsync uAPI.
From: Elizabeth Figura @ 2024-04-16 1:08 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan
Cc: linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Peter Zijlstra, Andy Lutomirski,
linux-doc, linux-kselftest, Randy Dunlap, Ingo Molnar,
Will Deacon, Waiman Long, Boqun Feng, Elizabeth Figura,
Bagas Sanjaya
In-Reply-To: <20240416010837.333694-1-zfigura@codeweavers.com>
Add an overall explanation of the driver architecture, and complete and precise
specification for its intended behaviour.
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
---
Documentation/userspace-api/index.rst | 1 +
Documentation/userspace-api/ntsync.rst | 399 +++++++++++++++++++++++++
2 files changed, 400 insertions(+)
create mode 100644 Documentation/userspace-api/ntsync.rst
diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst
index afecfe3cc4a8..d5745a500fa7 100644
--- a/Documentation/userspace-api/index.rst
+++ b/Documentation/userspace-api/index.rst
@@ -62,6 +62,7 @@ Everything else
vduse
futex2
perf_ring_buffer
+ ntsync
.. only:: subproject and html
diff --git a/Documentation/userspace-api/ntsync.rst b/Documentation/userspace-api/ntsync.rst
new file mode 100644
index 000000000000..202c2350d3af
--- /dev/null
+++ b/Documentation/userspace-api/ntsync.rst
@@ -0,0 +1,399 @@
+===================================
+NT synchronization primitive driver
+===================================
+
+This page documents the user-space API for the ntsync driver.
+
+ntsync is a support driver for emulation of NT synchronization
+primitives by user-space NT emulators. It exists because implementation
+in user-space, using existing tools, cannot match Windows performance
+while offering accurate semantics. It is implemented entirely in
+software, and does not drive any hardware device.
+
+This interface is meant as a compatibility tool only, and should not
+be used for general synchronization. Instead use generic, versatile
+interfaces such as futex(2) and poll(2).
+
+Synchronization primitives
+==========================
+
+The ntsync driver exposes three types of synchronization primitives:
+semaphores, mutexes, and events.
+
+A semaphore holds a single volatile 32-bit counter, and a static 32-bit
+integer denoting the maximum value. It is considered signaled when the
+counter is nonzero. The counter is decremented by one when a wait is
+satisfied. Both the initial and maximum count are established when the
+semaphore is created.
+
+A mutex holds a volatile 32-bit recursion count, and a volatile 32-bit
+identifier denoting its owner. A mutex is considered signaled when its
+owner is zero (indicating that it is not owned). The recursion count is
+incremented when a wait is satisfied, and ownership is set to the given
+identifier.
+
+A mutex also holds an internal flag denoting whether its previous owner
+has died; such a mutex is said to be abandoned. Owner death is not
+tracked automatically based on thread death, but rather must be
+communicated using ``NTSYNC_IOC_MUTEX_KILL``. An abandoned mutex is
+inherently considered unowned.
+
+Except for the "unowned" semantics of zero, the actual value of the
+owner identifier is not interpreted by the ntsync driver at all. The
+intended use is to store a thread identifier; however, the ntsync
+driver does not actually validate that a calling thread provides
+consistent or unique identifiers.
+
+An event holds a volatile boolean state denoting whether it is signaled
+or not. There are two types of events, auto-reset and manual-reset. An
+auto-reset event is designaled when a wait is satisfied; a manual-reset
+event is not. The event type is specified when the event is created.
+
+Unless specified otherwise, all operations on an object are atomic and
+totally ordered with respect to other operations on the same object.
+
+Objects are represented by files. When all file descriptors to an
+object are closed, that object is deleted.
+
+Char device
+===========
+
+The ntsync driver creates a single char device /dev/ntsync. Each file
+description opened on the device represents a unique instance intended
+to back an individual NT virtual machine. Objects created by one ntsync
+instance may only be used with other objects created by the same
+instance.
+
+ioctl reference
+===============
+
+All operations on the device are done through ioctls. There are four
+structures used in ioctl calls::
+
+ struct ntsync_sem_args {
+ __u32 sem;
+ __u32 count;
+ __u32 max;
+ };
+
+ struct ntsync_mutex_args {
+ __u32 mutex;
+ __u32 owner;
+ __u32 count;
+ };
+
+ struct ntsync_event_args {
+ __u32 event;
+ __u32 signaled;
+ __u32 manual;
+ };
+
+ struct ntsync_wait_args {
+ __u64 timeout;
+ __u64 objs;
+ __u32 count;
+ __u32 owner;
+ __u32 index;
+ __u32 alert;
+ __u32 flags;
+ __u32 pad;
+ };
+
+Depending on the ioctl, members of the structure may be used as input,
+output, or not at all. All ioctls return 0 on success.
+
+The ioctls on the device file are as follows:
+
+.. c:macro:: NTSYNC_IOC_CREATE_SEM
+
+ Create a semaphore object. Takes a pointer to struct
+ :c:type:`ntsync_sem_args`, which is used as follows:
+
+ .. list-table::
+
+ * - ``sem``
+ - On output, contains a file descriptor to the created semaphore.
+ * - ``count``
+ - Initial count of the semaphore.
+ * - ``max``
+ - Maximum count of the semaphore.
+
+ Fails with ``EINVAL`` if ``count`` is greater than ``max``.
+
+.. c:macro:: NTSYNC_IOC_CREATE_MUTEX
+
+ Create a mutex object. Takes a pointer to struct
+ :c:type:`ntsync_mutex_args`, which is used as follows:
+
+ .. list-table::
+
+ * - ``mutex``
+ - On output, contains a file descriptor to the created mutex.
+ * - ``count``
+ - Initial recursion count of the mutex.
+ * - ``owner``
+ - Initial owner of the mutex.
+
+ If ``owner`` is nonzero and ``count`` is zero, or if ``owner`` is
+ zero and ``count`` is nonzero, the function fails with ``EINVAL``.
+
+.. c:macro:: NTSYNC_IOC_CREATE_EVENT
+
+ Create an event object. Takes a pointer to struct
+ :c:type:`ntsync_event_args`, which is used as follows:
+
+ .. list-table::
+
+ * - ``event``
+ - On output, contains a file descriptor to the created event.
+ * - ``signaled``
+ - If nonzero, the event is initially signaled, otherwise
+ nonsignaled.
+ * - ``manual``
+ - If nonzero, the event is a manual-reset event, otherwise
+ auto-reset.
+
+The ioctls on the individual objects are as follows:
+
+.. c:macro:: NTSYNC_IOC_SEM_POST
+
+ Post to a semaphore object. Takes a pointer to a 32-bit integer,
+ which on input holds the count to be added to the semaphore, and on
+ output contains its previous count.
+
+ If adding to the semaphore's current count would raise the latter
+ past the semaphore's maximum count, the ioctl fails with
+ ``EOVERFLOW`` and the semaphore is not affected. If raising the
+ semaphore's count causes it to become signaled, eligible threads
+ waiting on this semaphore will be woken and the semaphore's count
+ decremented appropriately.
+
+.. c:macro:: NTSYNC_IOC_MUTEX_UNLOCK
+
+ Release a mutex object. Takes a pointer to struct
+ :c:type:`ntsync_mutex_args`, which is used as follows:
+
+ .. list-table::
+
+ * - ``mutex``
+ - Ignored.
+ * - ``owner``
+ - Specifies the owner trying to release this mutex.
+ * - ``count``
+ - On output, contains the previous recursion count.
+
+ If ``owner`` is zero, the ioctl fails with ``EINVAL``. If ``owner``
+ is not the current owner of the mutex, the ioctl fails with
+ ``EPERM``.
+
+ The mutex's count will be decremented by one. If decrementing the
+ mutex's count causes it to become zero, the mutex is marked as
+ unowned and signaled, and eligible threads waiting on it will be
+ woken as appropriate.
+
+.. c:macro:: NTSYNC_IOC_SET_EVENT
+
+ Signal an event object. Takes a pointer to a 32-bit integer, which on
+ output contains the previous state of the event.
+
+ Eligible threads will be woken, and auto-reset events will be
+ designaled appropriately.
+
+.. c:macro:: NTSYNC_IOC_RESET_EVENT
+
+ Designal an event object. Takes a pointer to a 32-bit integer, which
+ on output contains the previous state of the event.
+
+.. c:macro:: NTSYNC_IOC_PULSE_EVENT
+
+ Wake threads waiting on an event object while leaving it in an
+ unsignaled state. Takes a pointer to a 32-bit integer, which on
+ output contains the previous state of the event.
+
+ A pulse operation can be thought of as a set followed by a reset,
+ performed as a single atomic operation. If two threads are waiting on
+ an auto-reset event which is pulsed, only one will be woken. If two
+ threads are waiting a manual-reset event which is pulsed, both will
+ be woken. However, in both cases, the event will be unsignaled
+ afterwards, and a simultaneous read operation will always report the
+ event as unsignaled.
+
+.. c:macro:: NTSYNC_IOC_READ_SEM
+
+ Read the current state of a semaphore object. Takes a pointer to
+ struct :c:type:`ntsync_sem_args`, which is used as follows:
+
+ .. list-table::
+
+ * - ``sem``
+ - Ignored.
+ * - ``count``
+ - On output, contains the current count of the semaphore.
+ * - ``max``
+ - On output, contains the maximum count of the semaphore.
+
+.. c:macro:: NTSYNC_IOC_READ_MUTEX
+
+ Read the current state of a mutex object. Takes a pointer to struct
+ :c:type:`ntsync_mutex_args`, which is used as follows:
+
+ .. list-table::
+
+ * - ``mutex``
+ - Ignored.
+ * - ``owner``
+ - On output, contains the current owner of the mutex, or zero
+ if the mutex is not currently owned.
+ * - ``count``
+ - On output, contains the current recursion count of the mutex.
+
+ If the mutex is marked as abandoned, the function fails with
+ ``EOWNERDEAD``. In this case, ``count`` and ``owner`` are set to
+ zero.
+
+.. c:macro:: NTSYNC_IOC_READ_EVENT
+
+ Read the current state of an event object. Takes a pointer to struct
+ :c:type:`ntsync_event_args`, which is used as follows:
+
+ .. list-table::
+
+ * - ``event``
+ - Ignored.
+ * - ``signaled``
+ - On output, contains the current state of the event.
+ * - ``manual``
+ - On output, contains 1 if the event is a manual-reset event,
+ and 0 otherwise.
+
+.. c:macro:: NTSYNC_IOC_KILL_OWNER
+
+ Mark a mutex as unowned and abandoned if it is owned by the given
+ owner. Takes an input-only pointer to a 32-bit integer denoting the
+ owner. If the owner is zero, the ioctl fails with ``EINVAL``. If the
+ owner does not own the mutex, the function fails with ``EPERM``.
+
+ Eligible threads waiting on the mutex will be woken as appropriate
+ (and such waits will fail with ``EOWNERDEAD``, as described below).
+
+.. c:macro:: NTSYNC_IOC_WAIT_ANY
+
+ Poll on any of a list of objects, atomically acquiring at most one.
+ Takes a pointer to struct :c:type:`ntsync_wait_args`, which is
+ used as follows:
+
+ .. list-table::
+
+ * - ``timeout``
+ - Absolute timeout in nanoseconds. If ``NTSYNC_WAIT_REALTIME``
+ is set, the timeout is measured against the REALTIME clock;
+ otherwise it is measured against the MONOTONIC clock. If the
+ timeout is equal to or earlier than the current time, the
+ function returns immediately without sleeping. If ``timeout``
+ is U64_MAX, the function will sleep until an object is
+ signaled, and will not fail with ``ETIMEDOUT``.
+ * - ``objs``
+ - Pointer to an array of ``count`` file descriptors
+ (specified as an integer so that the structure has the same
+ size regardless of architecture). If any object is
+ invalid, the function fails with ``EINVAL``.
+ * - ``count``
+ - Number of objects specified in the ``objs`` array.
+ If greater than ``NTSYNC_MAX_WAIT_COUNT``, the function fails
+ with ``EINVAL``.
+ * - ``owner``
+ - Mutex owner identifier. If any object in ``objs`` is a mutex,
+ the ioctl will attempt to acquire that mutex on behalf of
+ ``owner``. If ``owner`` is zero, the ioctl fails with
+ ``EINVAL``.
+ * - ``index``
+ - On success, contains the index (into ``objs``) of the object
+ which was signaled. If ``alert`` was signaled instead,
+ this contains ``count``.
+ * - ``alert``
+ - Optional event object file descriptor. If nonzero, this
+ specifies an "alert" event object which, if signaled, will
+ terminate the wait. If nonzero, the identifier must point to a
+ valid event.
+ * - ``flags``
+ - Zero or more flags. Currently the only flag is
+ ``NTSYNC_WAIT_REALTIME``, which causes the timeout to be
+ measured against the REALTIME clock instead of MONOTONIC.
+ * - ``pad``
+ - Unused, must be set to zero.
+
+ This function attempts to acquire one of the given objects. If unable
+ to do so, it sleeps until an object becomes signaled, subsequently
+ acquiring it, or the timeout expires. In the latter case the ioctl
+ fails with ``ETIMEDOUT``. The function only acquires one object, even
+ if multiple objects are signaled.
+
+ A semaphore is considered to be signaled if its count is nonzero, and
+ is acquired by decrementing its count by one. A mutex is considered
+ to be signaled if it is unowned or if its owner matches the ``owner``
+ argument, and is acquired by incrementing its recursion count by one
+ and setting its owner to the ``owner`` argument. An auto-reset event
+ is acquired by designaling it; a manual-reset event is not affected
+ by acquisition.
+
+ Acquisition is atomic and totally ordered with respect to other
+ operations on the same object. If two wait operations (with different
+ ``owner`` identifiers) are queued on the same mutex, only one is
+ signaled. If two wait operations are queued on the same semaphore,
+ and a value of one is posted to it, only one is signaled. The order
+ in which threads are signaled is not specified.
+
+ If an abandoned mutex is acquired, the ioctl fails with
+ ``EOWNERDEAD``. Although this is a failure return, the function may
+ otherwise be considered successful. The mutex is marked as owned by
+ the given owner (with a recursion count of 1) and as no longer
+ abandoned, and ``index`` is still set to the index of the mutex.
+
+ The ``alert`` argument is an "extra" event which can terminate the
+ wait, independently of all other objects. If members of ``objs`` and
+ ``alert`` are both simultaneously signaled, a member of ``objs`` will
+ always be given priority and acquired first.
+
+ It is valid to pass the same object more than once, including by
+ passing the same event in the ``objs`` array and in ``alert``. If a
+ wakeup occurs due to that object being signaled, ``index`` is set to
+ the lowest index corresponding to that object.
+
+ The function may fail with ``EINTR`` if a signal is received.
+
+.. c:macro:: NTSYNC_IOC_WAIT_ALL
+
+ Poll on a list of objects, atomically acquiring all of them. Takes a
+ pointer to struct :c:type:`ntsync_wait_args`, which is used
+ identically to ``NTSYNC_IOC_WAIT_ANY``, except that ``index`` is
+ always filled with zero on success if not woken via alert.
+
+ This function attempts to simultaneously acquire all of the given
+ objects. If unable to do so, it sleeps until all objects become
+ simultaneously signaled, subsequently acquiring them, or the timeout
+ expires. In the latter case the ioctl fails with ``ETIMEDOUT`` and no
+ objects are modified.
+
+ Objects may become signaled and subsequently designaled (through
+ acquisition by other threads) while this thread is sleeping. Only
+ once all objects are simultaneously signaled does the ioctl acquire
+ them and return. The entire acquisition is atomic and totally ordered
+ with respect to other operations on any of the given objects.
+
+ If an abandoned mutex is acquired, the ioctl fails with
+ ``EOWNERDEAD``. Similarly to ``NTSYNC_IOC_WAIT_ANY``, all objects are
+ nevertheless marked as acquired. Note that if multiple mutex objects
+ are specified, there is no way to know which were marked as
+ abandoned.
+
+ As with "any" waits, the ``alert`` argument is an "extra" event which
+ can terminate the wait. Critically, however, an "all" wait will
+ succeed if all members in ``objs`` are signaled, *or* if ``alert`` is
+ signaled. In the latter case ``index`` will be set to ``count``. As
+ with "any" waits, if both conditions are filled, the former takes
+ priority, and objects in ``objs`` will be acquired.
+
+ Unlike ``NTSYNC_IOC_WAIT_ANY``, it is not valid to pass the same
+ object more than once, nor is it valid to pass the same object in
+ ``objs`` and in ``alert``. If this is attempted, the function fails
+ with ``EINVAL``.
--
2.43.0
^ permalink raw reply related
* [PATCH v4 26/27] maintainers: Add an entry for ntsync.
From: Elizabeth Figura @ 2024-04-16 1:08 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan
Cc: linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Peter Zijlstra, Andy Lutomirski,
linux-doc, linux-kselftest, Randy Dunlap, Ingo Molnar,
Will Deacon, Waiman Long, Boqun Feng, Elizabeth Figura
In-Reply-To: <20240416010837.333694-1-zfigura@codeweavers.com>
Add myself as maintainer, supported by CodeWeavers.
Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
---
MAINTAINERS | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index 41a013dfebbc..09ae011a8d91 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15728,6 +15728,15 @@ T: git https://github.com/Paragon-Software-Group/linux-ntfs3.git
F: Documentation/filesystems/ntfs3.rst
F: fs/ntfs3/
+NTSYNC SYNCHRONIZATION PRIMITIVE DRIVER
+M: Elizabeth Figura <zfigura@codeweavers.com>
+L: wine-devel@winehq.org
+S: Supported
+F: Documentation/userspace-api/ntsync.rst
+F: drivers/misc/ntsync.c
+F: include/uapi/linux/ntsync.h
+F: tools/testing/selftests/drivers/ntsync/
+
NUBUS SUBSYSTEM
M: Finn Thain <fthain@linux-m68k.org>
L: linux-m68k@lists.linux-m68k.org
--
2.43.0
^ permalink raw reply related
* [PATCH v4 23/27] selftests: ntsync: Add tests for alertable waits.
From: Elizabeth Figura @ 2024-04-16 1:08 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan
Cc: linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Peter Zijlstra, Andy Lutomirski,
linux-doc, linux-kselftest, Randy Dunlap, Ingo Molnar,
Will Deacon, Waiman Long, Boqun Feng, Elizabeth Figura
In-Reply-To: <20240416010837.333694-1-zfigura@codeweavers.com>
Test the "alert" functionality of NTSYNC_IOC_WAIT_ALL and NTSYNC_IOC_WAIT_ANY,
when a wait is woken with an alert and when it is woken by an object.
Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
---
.../testing/selftests/drivers/ntsync/ntsync.c | 179 +++++++++++++++++-
1 file changed, 176 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/drivers/ntsync/ntsync.c b/tools/testing/selftests/drivers/ntsync/ntsync.c
index 5d17eff6a370..5465a16d38b3 100644
--- a/tools/testing/selftests/drivers/ntsync/ntsync.c
+++ b/tools/testing/selftests/drivers/ntsync/ntsync.c
@@ -95,7 +95,7 @@ static int read_event_state(int event, __u32 *signaled, __u32 *manual)
})
static int wait_objs(int fd, unsigned long request, __u32 count,
- const int *objs, __u32 owner, __u32 *index)
+ const int *objs, __u32 owner, int alert, __u32 *index)
{
struct ntsync_wait_args args = {0};
struct timespec timeout;
@@ -108,6 +108,7 @@ static int wait_objs(int fd, unsigned long request, __u32 count,
args.objs = (uintptr_t)objs;
args.owner = owner;
args.index = 0xdeadbeef;
+ args.alert = alert;
ret = ioctl(fd, request, &args);
*index = args.index;
return ret;
@@ -115,12 +116,26 @@ static int wait_objs(int fd, unsigned long request, __u32 count,
static int wait_any(int fd, __u32 count, const int *objs, __u32 owner, __u32 *index)
{
- return wait_objs(fd, NTSYNC_IOC_WAIT_ANY, count, objs, owner, index);
+ return wait_objs(fd, NTSYNC_IOC_WAIT_ANY, count, objs, owner, 0, index);
}
static int wait_all(int fd, __u32 count, const int *objs, __u32 owner, __u32 *index)
{
- return wait_objs(fd, NTSYNC_IOC_WAIT_ALL, count, objs, owner, index);
+ return wait_objs(fd, NTSYNC_IOC_WAIT_ALL, count, objs, owner, 0, index);
+}
+
+static int wait_any_alert(int fd, __u32 count, const int *objs,
+ __u32 owner, int alert, __u32 *index)
+{
+ return wait_objs(fd, NTSYNC_IOC_WAIT_ANY,
+ count, objs, owner, alert, index);
+}
+
+static int wait_all_alert(int fd, __u32 count, const int *objs,
+ __u32 owner, int alert, __u32 *index)
+{
+ return wait_objs(fd, NTSYNC_IOC_WAIT_ALL,
+ count, objs, owner, alert, index);
}
TEST(semaphore_state)
@@ -1095,4 +1110,162 @@ TEST(wake_all)
close(fd);
}
+TEST(alert_any)
+{
+ struct ntsync_event_args event_args = {0};
+ struct ntsync_sem_args sem_args = {0};
+ __u32 index, count, signaled;
+ int objs[2], fd, ret;
+
+ fd = open("/dev/ntsync", O_CLOEXEC | O_RDONLY);
+ ASSERT_LE(0, fd);
+
+ sem_args.count = 0;
+ sem_args.max = 2;
+ sem_args.sem = 0xdeadbeef;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_SEM, &sem_args);
+ EXPECT_EQ(0, ret);
+ EXPECT_NE(0xdeadbeef, sem_args.sem);
+ objs[0] = sem_args.sem;
+
+ sem_args.count = 1;
+ sem_args.max = 2;
+ sem_args.sem = 0xdeadbeef;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_SEM, &sem_args);
+ EXPECT_EQ(0, ret);
+ EXPECT_NE(0xdeadbeef, sem_args.sem);
+ objs[1] = sem_args.sem;
+
+ event_args.manual = true;
+ event_args.signaled = true;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_EVENT, &event_args);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_any_alert(fd, 0, NULL, 123, event_args.event, &index);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, index);
+
+ ret = ioctl(event_args.event, NTSYNC_IOC_EVENT_RESET, &signaled);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_any_alert(fd, 0, NULL, 123, event_args.event, &index);
+ EXPECT_EQ(-1, ret);
+ EXPECT_EQ(ETIMEDOUT, errno);
+
+ ret = ioctl(event_args.event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_any_alert(fd, 2, objs, 123, event_args.event, &index);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(1, index);
+
+ ret = wait_any_alert(fd, 2, objs, 123, event_args.event, &index);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(2, index);
+
+ close(event_args.event);
+
+ /* test with an auto-reset event */
+
+ event_args.manual = false;
+ event_args.signaled = true;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_EVENT, &event_args);
+ EXPECT_EQ(0, ret);
+
+ count = 1;
+ ret = post_sem(objs[0], &count);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_any_alert(fd, 2, objs, 123, event_args.event, &index);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, index);
+
+ ret = wait_any_alert(fd, 2, objs, 123, event_args.event, &index);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(2, index);
+
+ ret = wait_any_alert(fd, 2, objs, 123, event_args.event, &index);
+ EXPECT_EQ(-1, ret);
+ EXPECT_EQ(ETIMEDOUT, errno);
+
+ close(event_args.event);
+
+ close(objs[0]);
+ close(objs[1]);
+
+ close(fd);
+}
+
+TEST(alert_all)
+{
+ struct ntsync_event_args event_args = {0};
+ struct ntsync_sem_args sem_args = {0};
+ __u32 index, count, signaled;
+ int objs[2], fd, ret;
+
+ fd = open("/dev/ntsync", O_CLOEXEC | O_RDONLY);
+ ASSERT_LE(0, fd);
+
+ sem_args.count = 2;
+ sem_args.max = 2;
+ sem_args.sem = 0xdeadbeef;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_SEM, &sem_args);
+ EXPECT_EQ(0, ret);
+ EXPECT_NE(0xdeadbeef, sem_args.sem);
+ objs[0] = sem_args.sem;
+
+ sem_args.count = 1;
+ sem_args.max = 2;
+ sem_args.sem = 0xdeadbeef;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_SEM, &sem_args);
+ EXPECT_EQ(0, ret);
+ EXPECT_NE(0xdeadbeef, sem_args.sem);
+ objs[1] = sem_args.sem;
+
+ event_args.manual = true;
+ event_args.signaled = true;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_EVENT, &event_args);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_all_alert(fd, 2, objs, 123, event_args.event, &index);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, index);
+
+ ret = wait_all_alert(fd, 2, objs, 123, event_args.event, &index);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(2, index);
+
+ close(event_args.event);
+
+ /* test with an auto-reset event */
+
+ event_args.manual = false;
+ event_args.signaled = true;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_EVENT, &event_args);
+ EXPECT_EQ(0, ret);
+
+ count = 2;
+ ret = post_sem(objs[1], &count);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_all_alert(fd, 2, objs, 123, event_args.event, &index);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, index);
+
+ ret = wait_all_alert(fd, 2, objs, 123, event_args.event, &index);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(2, index);
+
+ ret = wait_all_alert(fd, 2, objs, 123, event_args.event, &index);
+ EXPECT_EQ(-1, ret);
+ EXPECT_EQ(ETIMEDOUT, errno);
+
+ close(event_args.event);
+
+ close(objs[0]);
+ close(objs[1]);
+
+ close(fd);
+}
+
TEST_HARNESS_MAIN
--
2.43.0
^ permalink raw reply related
* [PATCH v4 24/27] selftests: ntsync: Add some tests for wakeup signaling via alerts.
From: Elizabeth Figura @ 2024-04-16 1:08 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan
Cc: linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Peter Zijlstra, Andy Lutomirski,
linux-doc, linux-kselftest, Randy Dunlap, Ingo Molnar,
Will Deacon, Waiman Long, Boqun Feng, Elizabeth Figura
In-Reply-To: <20240416010837.333694-1-zfigura@codeweavers.com>
Expand the alert tests to cover alerting a thread mid-wait, to test that the
relevant scheduling logic works correctly.
Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
---
.../testing/selftests/drivers/ntsync/ntsync.c | 62 +++++++++++++++++++
1 file changed, 62 insertions(+)
diff --git a/tools/testing/selftests/drivers/ntsync/ntsync.c b/tools/testing/selftests/drivers/ntsync/ntsync.c
index 5465a16d38b3..968874d7e325 100644
--- a/tools/testing/selftests/drivers/ntsync/ntsync.c
+++ b/tools/testing/selftests/drivers/ntsync/ntsync.c
@@ -1113,9 +1113,12 @@ TEST(wake_all)
TEST(alert_any)
{
struct ntsync_event_args event_args = {0};
+ struct ntsync_wait_args wait_args = {0};
struct ntsync_sem_args sem_args = {0};
__u32 index, count, signaled;
+ struct wait_args thread_args;
int objs[2], fd, ret;
+ pthread_t thread;
fd = open("/dev/ntsync", O_CLOEXEC | O_RDONLY);
ASSERT_LE(0, fd);
@@ -1163,6 +1166,34 @@ TEST(alert_any)
EXPECT_EQ(0, ret);
EXPECT_EQ(2, index);
+ /* test wakeup via alert */
+
+ ret = ioctl(event_args.event, NTSYNC_IOC_EVENT_RESET, &signaled);
+ EXPECT_EQ(0, ret);
+
+ wait_args.timeout = get_abs_timeout(1000);
+ wait_args.objs = (uintptr_t)objs;
+ wait_args.count = 2;
+ wait_args.owner = 123;
+ wait_args.index = 0xdeadbeef;
+ wait_args.alert = event_args.event;
+ thread_args.fd = fd;
+ thread_args.args = &wait_args;
+ thread_args.request = NTSYNC_IOC_WAIT_ANY;
+ ret = pthread_create(&thread, NULL, wait_thread, &thread_args);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_for_thread(thread, 100);
+ EXPECT_EQ(ETIMEDOUT, ret);
+
+ ret = ioctl(event_args.event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_for_thread(thread, 100);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, thread_args.ret);
+ EXPECT_EQ(2, wait_args.index);
+
close(event_args.event);
/* test with an auto-reset event */
@@ -1199,9 +1230,12 @@ TEST(alert_any)
TEST(alert_all)
{
struct ntsync_event_args event_args = {0};
+ struct ntsync_wait_args wait_args = {0};
struct ntsync_sem_args sem_args = {0};
+ struct wait_args thread_args;
__u32 index, count, signaled;
int objs[2], fd, ret;
+ pthread_t thread;
fd = open("/dev/ntsync", O_CLOEXEC | O_RDONLY);
ASSERT_LE(0, fd);
@@ -1235,6 +1269,34 @@ TEST(alert_all)
EXPECT_EQ(0, ret);
EXPECT_EQ(2, index);
+ /* test wakeup via alert */
+
+ ret = ioctl(event_args.event, NTSYNC_IOC_EVENT_RESET, &signaled);
+ EXPECT_EQ(0, ret);
+
+ wait_args.timeout = get_abs_timeout(1000);
+ wait_args.objs = (uintptr_t)objs;
+ wait_args.count = 2;
+ wait_args.owner = 123;
+ wait_args.index = 0xdeadbeef;
+ wait_args.alert = event_args.event;
+ thread_args.fd = fd;
+ thread_args.args = &wait_args;
+ thread_args.request = NTSYNC_IOC_WAIT_ALL;
+ ret = pthread_create(&thread, NULL, wait_thread, &thread_args);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_for_thread(thread, 100);
+ EXPECT_EQ(ETIMEDOUT, ret);
+
+ ret = ioctl(event_args.event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_for_thread(thread, 100);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, thread_args.ret);
+ EXPECT_EQ(2, wait_args.index);
+
close(event_args.event);
/* test with an auto-reset event */
--
2.43.0
^ permalink raw reply related
* [PATCH v4 25/27] selftests: ntsync: Add a stress test for contended waits.
From: Elizabeth Figura @ 2024-04-16 1:08 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan
Cc: linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Peter Zijlstra, Andy Lutomirski,
linux-doc, linux-kselftest, Randy Dunlap, Ingo Molnar,
Will Deacon, Waiman Long, Boqun Feng, Elizabeth Figura
In-Reply-To: <20240416010837.333694-1-zfigura@codeweavers.com>
Test a more realistic usage pattern, and one with heavy contention, in order to
actually exercise ntsync's internal synchronization.
This test has several threads in a tight loop acquiring a mutex, modifying some
shared data, and then releasing the mutex. At the end we check if the data is
consistent.
Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
---
.../testing/selftests/drivers/ntsync/ntsync.c | 74 +++++++++++++++++++
1 file changed, 74 insertions(+)
diff --git a/tools/testing/selftests/drivers/ntsync/ntsync.c b/tools/testing/selftests/drivers/ntsync/ntsync.c
index 968874d7e325..5fa2c9a0768c 100644
--- a/tools/testing/selftests/drivers/ntsync/ntsync.c
+++ b/tools/testing/selftests/drivers/ntsync/ntsync.c
@@ -1330,4 +1330,78 @@ TEST(alert_all)
close(fd);
}
+#define STRESS_LOOPS 10000
+#define STRESS_THREADS 4
+
+static unsigned int stress_counter;
+static int stress_device, stress_start_event, stress_mutex;
+
+static void *stress_thread(void *arg)
+{
+ struct ntsync_wait_args wait_args = {0};
+ __u32 index, count, i;
+ int ret;
+
+ wait_args.timeout = UINT64_MAX;
+ wait_args.count = 1;
+ wait_args.objs = (uintptr_t)&stress_start_event;
+ wait_args.owner = gettid();
+ wait_args.index = 0xdeadbeef;
+
+ ioctl(stress_device, NTSYNC_IOC_WAIT_ANY, &wait_args);
+
+ wait_args.objs = (uintptr_t)&stress_mutex;
+
+ for (i = 0; i < STRESS_LOOPS; ++i) {
+ ioctl(stress_device, NTSYNC_IOC_WAIT_ANY, &wait_args);
+
+ ++stress_counter;
+
+ unlock_mutex(stress_mutex, wait_args.owner, &count);
+ }
+
+ return NULL;
+}
+
+TEST(stress_wait)
+{
+ struct ntsync_event_args event_args;
+ struct ntsync_mutex_args mutex_args;
+ pthread_t threads[STRESS_THREADS];
+ __u32 signaled, i;
+ int ret;
+
+ stress_device = open("/dev/ntsync", O_CLOEXEC | O_RDONLY);
+ ASSERT_LE(0, stress_device);
+
+ mutex_args.owner = 0;
+ mutex_args.count = 0;
+ ret = ioctl(stress_device, NTSYNC_IOC_CREATE_MUTEX, &mutex_args);
+ EXPECT_EQ(0, ret);
+ stress_mutex = mutex_args.mutex;
+
+ event_args.manual = 1;
+ event_args.signaled = 0;
+ ret = ioctl(stress_device, NTSYNC_IOC_CREATE_EVENT, &event_args);
+ EXPECT_EQ(0, ret);
+ stress_start_event = event_args.event;
+
+ for (i = 0; i < STRESS_THREADS; ++i)
+ pthread_create(&threads[i], NULL, stress_thread, NULL);
+
+ ret = ioctl(stress_start_event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+
+ for (i = 0; i < STRESS_THREADS; ++i) {
+ ret = pthread_join(threads[i], NULL);
+ EXPECT_EQ(0, ret);
+ }
+
+ EXPECT_EQ(STRESS_LOOPS * STRESS_THREADS, stress_counter);
+
+ close(stress_start_event);
+ close(stress_mutex);
+ close(stress_device);
+}
+
TEST_HARNESS_MAIN
--
2.43.0
^ permalink raw reply related
* [PATCH v4 20/27] selftests: ntsync: Add some tests for manual-reset event state.
From: Elizabeth Figura @ 2024-04-16 1:08 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan
Cc: linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Peter Zijlstra, Andy Lutomirski,
linux-doc, linux-kselftest, Randy Dunlap, Ingo Molnar,
Will Deacon, Waiman Long, Boqun Feng, Elizabeth Figura
In-Reply-To: <20240416010837.333694-1-zfigura@codeweavers.com>
Test event-specific ioctls NTSYNC_IOC_EVENT_SET, NTSYNC_IOC_EVENT_RESET,
NTSYNC_IOC_EVENT_PULSE, NTSYNC_IOC_EVENT_READ for manual-reset events, and
waiting on manual-reset events.
Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
---
.../testing/selftests/drivers/ntsync/ntsync.c | 89 +++++++++++++++++++
1 file changed, 89 insertions(+)
diff --git a/tools/testing/selftests/drivers/ntsync/ntsync.c b/tools/testing/selftests/drivers/ntsync/ntsync.c
index b77fb0b2c4b1..b6481c2b85cc 100644
--- a/tools/testing/selftests/drivers/ntsync/ntsync.c
+++ b/tools/testing/selftests/drivers/ntsync/ntsync.c
@@ -73,6 +73,27 @@ static int unlock_mutex(int mutex, __u32 owner, __u32 *count)
return ret;
}
+static int read_event_state(int event, __u32 *signaled, __u32 *manual)
+{
+ struct ntsync_event_args args;
+ int ret;
+
+ memset(&args, 0xcc, sizeof(args));
+ ret = ioctl(event, NTSYNC_IOC_EVENT_READ, &args);
+ *signaled = args.signaled;
+ *manual = args.manual;
+ return ret;
+}
+
+#define check_event_state(event, signaled, manual) \
+ ({ \
+ __u32 __signaled, __manual; \
+ int ret = read_event_state((event), &__signaled, &__manual); \
+ EXPECT_EQ(0, ret); \
+ EXPECT_EQ((signaled), __signaled); \
+ EXPECT_EQ((manual), __manual); \
+ })
+
static int wait_objs(int fd, unsigned long request, __u32 count,
const int *objs, __u32 owner, __u32 *index)
{
@@ -353,6 +374,74 @@ TEST(mutex_state)
close(fd);
}
+TEST(manual_event_state)
+{
+ struct ntsync_event_args event_args;
+ __u32 index, signaled;
+ int fd, event, ret;
+
+ fd = open("/dev/ntsync", O_CLOEXEC | O_RDONLY);
+ ASSERT_LE(0, fd);
+
+ event_args.manual = 1;
+ event_args.signaled = 0;
+ event_args.event = 0xdeadbeef;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_EVENT, &event_args);
+ EXPECT_EQ(0, ret);
+ EXPECT_NE(0xdeadbeef, event_args.event);
+ event = event_args.event;
+ check_event_state(event, 0, 1);
+
+ signaled = 0xdeadbeef;
+ ret = ioctl(event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+ check_event_state(event, 1, 1);
+
+ ret = ioctl(event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(1, signaled);
+ check_event_state(event, 1, 1);
+
+ ret = wait_any(fd, 1, &event, 123, &index);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, index);
+ check_event_state(event, 1, 1);
+
+ signaled = 0xdeadbeef;
+ ret = ioctl(event, NTSYNC_IOC_EVENT_RESET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(1, signaled);
+ check_event_state(event, 0, 1);
+
+ ret = ioctl(event, NTSYNC_IOC_EVENT_RESET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+ check_event_state(event, 0, 1);
+
+ ret = wait_any(fd, 1, &event, 123, &index);
+ EXPECT_EQ(-1, ret);
+ EXPECT_EQ(ETIMEDOUT, errno);
+
+ ret = ioctl(event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+
+ ret = ioctl(event, NTSYNC_IOC_EVENT_PULSE, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(1, signaled);
+ check_event_state(event, 0, 1);
+
+ ret = ioctl(event, NTSYNC_IOC_EVENT_PULSE, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+ check_event_state(event, 0, 1);
+
+ close(event);
+
+ close(fd);
+}
+
TEST(test_wait_any)
{
int objs[NTSYNC_MAX_WAIT_COUNT + 1], fd, ret;
--
2.43.0
^ permalink raw reply related
* [PATCH v4 22/27] selftests: ntsync: Add some tests for wakeup signaling with events.
From: Elizabeth Figura @ 2024-04-16 1:08 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan
Cc: linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Peter Zijlstra, Andy Lutomirski,
linux-doc, linux-kselftest, Randy Dunlap, Ingo Molnar,
Will Deacon, Waiman Long, Boqun Feng, Elizabeth Figura
In-Reply-To: <20240416010837.333694-1-zfigura@codeweavers.com>
Expand the contended wait tests, which previously only covered events and
semaphores, to cover events as well.
Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
---
.../testing/selftests/drivers/ntsync/ntsync.c | 151 +++++++++++++++++-
1 file changed, 147 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/drivers/ntsync/ntsync.c b/tools/testing/selftests/drivers/ntsync/ntsync.c
index 12ccb4ec28e4..5d17eff6a370 100644
--- a/tools/testing/selftests/drivers/ntsync/ntsync.c
+++ b/tools/testing/selftests/drivers/ntsync/ntsync.c
@@ -622,6 +622,7 @@ TEST(test_wait_any)
TEST(test_wait_all)
{
+ struct ntsync_event_args event_args = {0};
struct ntsync_mutex_args mutex_args = {0};
struct ntsync_sem_args sem_args = {0};
__u32 owner, index, count;
@@ -644,6 +645,11 @@ TEST(test_wait_all)
EXPECT_EQ(0, ret);
EXPECT_NE(0xdeadbeef, mutex_args.mutex);
+ event_args.manual = true;
+ event_args.signaled = true;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_EVENT, &event_args);
+ EXPECT_EQ(0, ret);
+
objs[0] = sem_args.sem;
objs[1] = mutex_args.mutex;
@@ -692,6 +698,14 @@ TEST(test_wait_all)
check_sem_state(sem_args.sem, 1, 3);
check_mutex_state(mutex_args.mutex, 1, 123);
+ objs[0] = sem_args.sem;
+ objs[1] = event_args.event;
+ ret = wait_all(fd, 2, objs, 123, &index);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, index);
+ check_sem_state(sem_args.sem, 0, 3);
+ check_event_state(event_args.event, 1, 1);
+
/* test waiting on the same object twice */
objs[0] = objs[1] = sem_args.sem;
ret = wait_all(fd, 2, objs, 123, &index);
@@ -700,6 +714,7 @@ TEST(test_wait_all)
close(sem_args.sem);
close(mutex_args.mutex);
+ close(event_args.event);
close(fd);
}
@@ -746,12 +761,13 @@ static int wait_for_thread(pthread_t thread, unsigned int ms)
TEST(wake_any)
{
+ struct ntsync_event_args event_args = {0};
struct ntsync_mutex_args mutex_args = {0};
struct ntsync_wait_args wait_args = {0};
struct ntsync_sem_args sem_args = {0};
struct wait_args thread_args;
+ __u32 count, index, signaled;
int objs[2], fd, ret;
- __u32 count, index;
pthread_t thread;
fd = open("/dev/ntsync", O_CLOEXEC | O_RDONLY);
@@ -833,10 +849,101 @@ TEST(wake_any)
EXPECT_EQ(0, thread_args.ret);
EXPECT_EQ(1, wait_args.index);
+ /* test waking events */
+
+ event_args.manual = false;
+ event_args.signaled = false;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_EVENT, &event_args);
+ EXPECT_EQ(0, ret);
+
+ objs[1] = event_args.event;
+ wait_args.timeout = get_abs_timeout(1000);
+ ret = pthread_create(&thread, NULL, wait_thread, &thread_args);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_for_thread(thread, 100);
+ EXPECT_EQ(ETIMEDOUT, ret);
+
+ ret = ioctl(event_args.event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+ check_event_state(event_args.event, 0, 0);
+
+ ret = wait_for_thread(thread, 100);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, thread_args.ret);
+ EXPECT_EQ(1, wait_args.index);
+
+ wait_args.timeout = get_abs_timeout(1000);
+ ret = pthread_create(&thread, NULL, wait_thread, &thread_args);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_for_thread(thread, 100);
+ EXPECT_EQ(ETIMEDOUT, ret);
+
+ ret = ioctl(event_args.event, NTSYNC_IOC_EVENT_PULSE, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+ check_event_state(event_args.event, 0, 0);
+
+ ret = wait_for_thread(thread, 100);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, thread_args.ret);
+ EXPECT_EQ(1, wait_args.index);
+
+ close(event_args.event);
+
+ event_args.manual = true;
+ event_args.signaled = false;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_EVENT, &event_args);
+ EXPECT_EQ(0, ret);
+
+ objs[1] = event_args.event;
+ wait_args.timeout = get_abs_timeout(1000);
+ ret = pthread_create(&thread, NULL, wait_thread, &thread_args);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_for_thread(thread, 100);
+ EXPECT_EQ(ETIMEDOUT, ret);
+
+ ret = ioctl(event_args.event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+ check_event_state(event_args.event, 1, 1);
+
+ ret = wait_for_thread(thread, 100);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, thread_args.ret);
+ EXPECT_EQ(1, wait_args.index);
+
+ ret = ioctl(event_args.event, NTSYNC_IOC_EVENT_RESET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(1, signaled);
+
+ wait_args.timeout = get_abs_timeout(1000);
+ ret = pthread_create(&thread, NULL, wait_thread, &thread_args);
+ EXPECT_EQ(0, ret);
+
+ ret = wait_for_thread(thread, 100);
+ EXPECT_EQ(ETIMEDOUT, ret);
+
+ ret = ioctl(event_args.event, NTSYNC_IOC_EVENT_PULSE, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+ check_event_state(event_args.event, 0, 1);
+
+ ret = wait_for_thread(thread, 100);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, thread_args.ret);
+ EXPECT_EQ(1, wait_args.index);
+
+ close(event_args.event);
+
/* delete an object while it's being waited on */
wait_args.timeout = get_abs_timeout(200);
wait_args.owner = 123;
+ objs[1] = mutex_args.mutex;
ret = pthread_create(&thread, NULL, wait_thread, &thread_args);
EXPECT_EQ(0, ret);
@@ -856,12 +963,14 @@ TEST(wake_any)
TEST(wake_all)
{
+ struct ntsync_event_args manual_event_args = {0};
+ struct ntsync_event_args auto_event_args = {0};
struct ntsync_mutex_args mutex_args = {0};
struct ntsync_wait_args wait_args = {0};
struct ntsync_sem_args sem_args = {0};
struct wait_args thread_args;
- int objs[2], fd, ret;
- __u32 count, index;
+ __u32 count, index, signaled;
+ int objs[4], fd, ret;
pthread_t thread;
fd = open("/dev/ntsync", O_CLOEXEC | O_RDONLY);
@@ -881,12 +990,24 @@ TEST(wake_all)
EXPECT_EQ(0, ret);
EXPECT_NE(0xdeadbeef, mutex_args.mutex);
+ manual_event_args.manual = true;
+ manual_event_args.signaled = true;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_EVENT, &manual_event_args);
+ EXPECT_EQ(0, ret);
+
+ auto_event_args.manual = false;
+ auto_event_args.signaled = true;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_EVENT, &auto_event_args);
+ EXPECT_EQ(0, ret);
+
objs[0] = sem_args.sem;
objs[1] = mutex_args.mutex;
+ objs[2] = manual_event_args.event;
+ objs[3] = auto_event_args.event;
wait_args.timeout = get_abs_timeout(1000);
wait_args.objs = (uintptr_t)objs;
- wait_args.count = 2;
+ wait_args.count = 4;
wait_args.owner = 456;
thread_args.fd = fd;
thread_args.args = &wait_args;
@@ -920,12 +1041,32 @@ TEST(wake_all)
check_mutex_state(mutex_args.mutex, 0, 0);
+ ret = ioctl(manual_event_args.event, NTSYNC_IOC_EVENT_RESET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(1, signaled);
+
count = 2;
ret = post_sem(sem_args.sem, &count);
EXPECT_EQ(0, ret);
EXPECT_EQ(0, count);
+ check_sem_state(sem_args.sem, 2, 3);
+
+ ret = ioctl(auto_event_args.event, NTSYNC_IOC_EVENT_RESET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(1, signaled);
+
+ ret = ioctl(manual_event_args.event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+
+ ret = ioctl(auto_event_args.event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+
check_sem_state(sem_args.sem, 1, 3);
check_mutex_state(mutex_args.mutex, 1, 456);
+ check_event_state(manual_event_args.event, 1, 1);
+ check_event_state(auto_event_args.event, 0, 0);
ret = wait_for_thread(thread, 100);
EXPECT_EQ(0, ret);
@@ -943,6 +1084,8 @@ TEST(wake_all)
close(sem_args.sem);
close(mutex_args.mutex);
+ close(manual_event_args.event);
+ close(auto_event_args.event);
ret = wait_for_thread(thread, 200);
EXPECT_EQ(0, ret);
--
2.43.0
^ permalink raw reply related
* [PATCH v4 21/27] selftests: ntsync: Add some tests for auto-reset event state.
From: Elizabeth Figura @ 2024-04-16 1:08 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan
Cc: linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Peter Zijlstra, Andy Lutomirski,
linux-doc, linux-kselftest, Randy Dunlap, Ingo Molnar,
Will Deacon, Waiman Long, Boqun Feng, Elizabeth Figura
In-Reply-To: <20240416010837.333694-1-zfigura@codeweavers.com>
Test event-specific ioctls NTSYNC_IOC_EVENT_SET, NTSYNC_IOC_EVENT_RESET,
NTSYNC_IOC_EVENT_PULSE, NTSYNC_IOC_EVENT_READ for auto-reset events, and
waiting on auto-reset events.
Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
---
.../testing/selftests/drivers/ntsync/ntsync.c | 59 +++++++++++++++++++
1 file changed, 59 insertions(+)
diff --git a/tools/testing/selftests/drivers/ntsync/ntsync.c b/tools/testing/selftests/drivers/ntsync/ntsync.c
index b6481c2b85cc..12ccb4ec28e4 100644
--- a/tools/testing/selftests/drivers/ntsync/ntsync.c
+++ b/tools/testing/selftests/drivers/ntsync/ntsync.c
@@ -442,6 +442,65 @@ TEST(manual_event_state)
close(fd);
}
+TEST(auto_event_state)
+{
+ struct ntsync_event_args event_args;
+ __u32 index, signaled;
+ int fd, event, ret;
+
+ fd = open("/dev/ntsync", O_CLOEXEC | O_RDONLY);
+ ASSERT_LE(0, fd);
+
+ event_args.manual = 0;
+ event_args.signaled = 1;
+ event_args.event = 0xdeadbeef;
+ ret = ioctl(fd, NTSYNC_IOC_CREATE_EVENT, &event_args);
+ EXPECT_EQ(0, ret);
+ EXPECT_NE(0xdeadbeef, event_args.event);
+ event = event_args.event;
+
+ check_event_state(event, 1, 0);
+
+ signaled = 0xdeadbeef;
+ ret = ioctl(event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(1, signaled);
+ check_event_state(event, 1, 0);
+
+ ret = wait_any(fd, 1, &event, 123, &index);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, index);
+ check_event_state(event, 0, 0);
+
+ signaled = 0xdeadbeef;
+ ret = ioctl(event, NTSYNC_IOC_EVENT_RESET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+ check_event_state(event, 0, 0);
+
+ ret = wait_any(fd, 1, &event, 123, &index);
+ EXPECT_EQ(-1, ret);
+ EXPECT_EQ(ETIMEDOUT, errno);
+
+ ret = ioctl(event, NTSYNC_IOC_EVENT_SET, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+
+ ret = ioctl(event, NTSYNC_IOC_EVENT_PULSE, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(1, signaled);
+ check_event_state(event, 0, 0);
+
+ ret = ioctl(event, NTSYNC_IOC_EVENT_PULSE, &signaled);
+ EXPECT_EQ(0, ret);
+ EXPECT_EQ(0, signaled);
+ check_event_state(event, 0, 0);
+
+ close(event);
+
+ close(fd);
+}
+
TEST(test_wait_any)
{
int objs[NTSYNC_MAX_WAIT_COUNT + 1], fd, ret;
--
2.43.0
^ permalink raw reply related
* [PATCH v4 00/30] NT synchronization primitive driver
From: Elizabeth Figura @ 2024-04-16 1:08 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan
Cc: linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Peter Zijlstra, Andy Lutomirski,
linux-doc, linux-kselftest, Randy Dunlap, Ingo Molnar,
Will Deacon, Waiman Long, Boqun Feng, Elizabeth Figura
This patch series implements a new char misc driver, /dev/ntsync, which is used
to implement Windows NT synchronization primitives.
NT synchronization primitives are unique in that the wait functions both are
vectored, operate on multiple types of object with different behaviour (mutex,
semaphore, event), and affect the state of the objects they wait on. This model
is not compatible with existing kernel synchronization objects or interfaces,
and therefore the ntsync driver implements its own wait queues and locking.
Hence I would like to request review from someone familiar with locking to make
sure that the usage of low-level kernel primitives is correct and that the wait
queues work as intended, and to that end I've CC'd the locking maintainers.
== Background ==
The Wine project emulates the Windows API in user space. One particular part of
that API, namely the NT synchronization primitives, have historically been
implemented via RPC to a dedicated "kernel" process. However, more recent
applications use these APIs more strenuously, and the overhead of RPC has become
a bottleneck.
The NT synchronization APIs are too complex to implement on top of existing
primitives without sacrificing correctness. Certain operations, such as
NtPulseEvent() or the "wait-for-all" mode of NtWaitForMultipleObjects(), require
direct control over the underlying wait queue, and implementing a wait queue
sufficiently robust for Wine in user space is not possible. This proposed
driver, therefore, implements the problematic interfaces directly in the Linux
kernel.
This driver was presented at Linux Plumbers Conference 2023. For those further
interested in the history of synchronization in Wine and past attempts to solve
this problem in user space, a recording of the presentation can be viewed here:
https://www.youtube.com/watch?v=NjU4nyWyhU8
== Performance ==
The gain in performance varies wildly depending on the application in question
and the user's hardware. For some games NT synchronization is not a bottleneck
and no change can be observed, but for others frame rate improvements of 50 to
150 percent are not atypical. The following table lists frame rate measurements
from a variety of games on a variety of hardware, taken by users Dmitry
Skvortsov, FuzzyQuils, OnMars, and myself:
Game Upstream ntsync improvement
===========================================================================
Anger Foot 69 99 43%
Call of Juarez 99.8 224.1 125%
Dirt 3 110.6 860.7 678%
Forza Horizon 5 108 160 48%
Lara Croft: Temple of Osiris 141 326 131%
Metro 2033 164.4 199.2 21%
Resident Evil 2 26 77 196%
The Crew 26 51 96%
Tiny Tina's Wonderlands 130 360 177%
Total War Saga: Troy 109 146 34%
===========================================================================
== Patches ==
The intended semantics of the patches are broadly intended to match those of the
corresponding Windows functions. For those not already familiar with the Windows
functions (or their undocumented behaviour), patch 27/27 provides a detailed
specification, and individual patches also include a brief description of the
API they are implementing.
The patches making use of this driver in Wine can be retrieved or browsed here:
https://repo.or.cz/wine/zf.git/shortlog/refs/heads/ntsync5
== Implementation ==
Some aspects of the implementation may deserve particular comment:
* In the interest of performance, each object is governed only by a single
spinlock. However, NTSYNC_IOC_WAIT_ALL requires that the state of multiple
objects be changed as a single atomic operation. In order to achieve this, we
first take a device-wide lock ("wait_all_lock") any time we are going to lock
more than one object at a time.
The maximum number of objects that can be used in a vectored wait, and
therefore the maximum that can be locked simultaneously, is 64. This number is
NT's own limit.
The acquisition of multiple spinlocks will degrade performance. This is a
conscious choice, however. Wait-for-all is known to be a very rare operation
in practice, especially with counts that approach the maximum, and it is the
intent of the ntsync driver to optimize wait-for-any at the expense of
wait-for-all as much as possible.
* NT mutexes are tied to their threads on an OS level, and the kernel includes
builtin support for "robust" mutexes. In order to keep the ntsync driver
self-contained and avoid touching more code than necessary, it does not hook
into task exit nor use pids.
Instead, the user space emulator is expected to manage thread IDs and pass
them as an argument to any relevant functions; this is the "owner" field of
ntsync_wait_args and ntsync_mutex_args.
When the emulator detects that a thread dies, it should therefore call
NTSYNC_IOC_MUTEX_KILL on any open mutexes.
* ntsync is module-capable mostly because there was nothing preventing it, and
because it aided development. It is not a hard requirement, though.
== Previous versions ==
Changes from v3:
* Add .gitignore and use KHDR_INCLUDES in selftest build files, per Muhammad
Usama Anjum.
* Try to explain why we are rolling our own primitives a little better, per Greg
Kroah-Hartman.
* Link to v3: https://lore.kernel.org/lkml/20240329000621.148791-1-zfigura@codeweavers.com/
* Link to v2: https://lore.kernel.org/lkml/20240219223833.95710-1-zfigura@codeweavers.com/
* Link to v1: https://lore.kernel.org/lkml/20240214233645.9273-1-zfigura@codeweavers.com/
* Link to RFC v2: https://lore.kernel.org/lkml/20240131021356.10322-1-zfigura@codeweavers.com/
* Link to RFC v1: https://lore.kernel.org/lkml/20240124004028.16826-1-zfigura@codeweavers.com/
Elizabeth Figura (27):
ntsync: Introduce NTSYNC_IOC_WAIT_ANY.
ntsync: Introduce NTSYNC_IOC_WAIT_ALL.
ntsync: Introduce NTSYNC_IOC_CREATE_MUTEX.
ntsync: Introduce NTSYNC_IOC_MUTEX_UNLOCK.
ntsync: Introduce NTSYNC_IOC_MUTEX_KILL.
ntsync: Introduce NTSYNC_IOC_CREATE_EVENT.
ntsync: Introduce NTSYNC_IOC_EVENT_SET.
ntsync: Introduce NTSYNC_IOC_EVENT_RESET.
ntsync: Introduce NTSYNC_IOC_EVENT_PULSE.
ntsync: Introduce NTSYNC_IOC_SEM_READ.
ntsync: Introduce NTSYNC_IOC_MUTEX_READ.
ntsync: Introduce NTSYNC_IOC_EVENT_READ.
ntsync: Introduce alertable waits.
selftests: ntsync: Add some tests for semaphore state.
selftests: ntsync: Add some tests for mutex state.
selftests: ntsync: Add some tests for NTSYNC_IOC_WAIT_ANY.
selftests: ntsync: Add some tests for NTSYNC_IOC_WAIT_ALL.
selftests: ntsync: Add some tests for wakeup signaling with
WINESYNC_IOC_WAIT_ANY.
selftests: ntsync: Add some tests for wakeup signaling with
WINESYNC_IOC_WAIT_ALL.
selftests: ntsync: Add some tests for manual-reset event state.
selftests: ntsync: Add some tests for auto-reset event state.
selftests: ntsync: Add some tests for wakeup signaling with events.
selftests: ntsync: Add tests for alertable waits.
selftests: ntsync: Add some tests for wakeup signaling via alerts.
selftests: ntsync: Add a stress test for contended waits.
maintainers: Add an entry for ntsync.
docs: ntsync: Add documentation for the ntsync uAPI.
Documentation/userspace-api/index.rst | 1 +
Documentation/userspace-api/ntsync.rst | 399 +++++
MAINTAINERS | 9 +
drivers/misc/ntsync.c | 925 ++++++++++-
include/uapi/linux/ntsync.h | 39 +
tools/testing/selftests/Makefile | 1 +
.../selftests/drivers/ntsync/.gitignore | 1 +
.../testing/selftests/drivers/ntsync/Makefile | 7 +
tools/testing/selftests/drivers/ntsync/config | 1 +
.../testing/selftests/drivers/ntsync/ntsync.c | 1407 +++++++++++++++++
10 files changed, 2786 insertions(+), 4 deletions(-)
create mode 100644 Documentation/userspace-api/ntsync.rst
create mode 100644 tools/testing/selftests/drivers/ntsync/.gitignore
create mode 100644 tools/testing/selftests/drivers/ntsync/Makefile
create mode 100644 tools/testing/selftests/drivers/ntsync/config
create mode 100644 tools/testing/selftests/drivers/ntsync/ntsync.c
base-commit: ebbc1a4789c666846b9854ef845a37a64879e5f9
--
2.43.0
^ permalink raw reply
* [PATCH v4 09/27] ntsync: Introduce NTSYNC_IOC_EVENT_PULSE.
From: Elizabeth Figura @ 2024-04-16 1:08 UTC (permalink / raw)
To: Arnd Bergmann, Greg Kroah-Hartman, Jonathan Corbet, Shuah Khan
Cc: linux-kernel, linux-api, wine-devel, André Almeida,
Wolfram Sang, Arkadiusz Hiler, Peter Zijlstra, Andy Lutomirski,
linux-doc, linux-kselftest, Randy Dunlap, Ingo Molnar,
Will Deacon, Waiman Long, Boqun Feng, Elizabeth Figura
In-Reply-To: <20240416010837.333694-1-zfigura@codeweavers.com>
This corresponds to the NT syscall NtPulseEvent().
This wakes up any waiters as if the event had been set, but does not set the
event, instead resetting it if it had been signalled. Thus, for a manual-reset
event, all waiters are woken, whereas for an auto-reset event, at most one
waiter is woken.
Signed-off-by: Elizabeth Figura <zfigura@codeweavers.com>
---
drivers/misc/ntsync.c | 10 ++++++++--
include/uapi/linux/ntsync.h | 1 +
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c
index ae78425c87d1..adba4657bf26 100644
--- a/drivers/misc/ntsync.c
+++ b/drivers/misc/ntsync.c
@@ -473,7 +473,7 @@ static int ntsync_mutex_kill(struct ntsync_obj *mutex, void __user *argp)
return ret;
}
-static int ntsync_event_set(struct ntsync_obj *event, void __user *argp)
+static int ntsync_event_set(struct ntsync_obj *event, void __user *argp, bool pulse)
{
struct ntsync_device *dev = event->dev;
__u32 prev_state;
@@ -489,6 +489,8 @@ static int ntsync_event_set(struct ntsync_obj *event, void __user *argp)
event->u.event.signaled = true;
try_wake_all_obj(dev, event);
try_wake_any_event(event);
+ if (pulse)
+ event->u.event.signaled = false;
spin_unlock(&event->lock);
spin_unlock(&dev->wait_all_lock);
@@ -498,6 +500,8 @@ static int ntsync_event_set(struct ntsync_obj *event, void __user *argp)
prev_state = event->u.event.signaled;
event->u.event.signaled = true;
try_wake_any_event(event);
+ if (pulse)
+ event->u.event.signaled = false;
spin_unlock(&event->lock);
}
@@ -552,9 +556,11 @@ static long ntsync_obj_ioctl(struct file *file, unsigned int cmd,
case NTSYNC_IOC_MUTEX_KILL:
return ntsync_mutex_kill(obj, argp);
case NTSYNC_IOC_EVENT_SET:
- return ntsync_event_set(obj, argp);
+ return ntsync_event_set(obj, argp, false);
case NTSYNC_IOC_EVENT_RESET:
return ntsync_event_reset(obj, argp);
+ case NTSYNC_IOC_EVENT_PULSE:
+ return ntsync_event_set(obj, argp, true);
default:
return -ENOIOCTLCMD;
}
diff --git a/include/uapi/linux/ntsync.h b/include/uapi/linux/ntsync.h
index 657542107328..57721f5d31ba 100644
--- a/include/uapi/linux/ntsync.h
+++ b/include/uapi/linux/ntsync.h
@@ -54,5 +54,6 @@ struct ntsync_wait_args {
#define NTSYNC_IOC_MUTEX_KILL _IOW ('N', 0x86, __u32)
#define NTSYNC_IOC_EVENT_SET _IOR ('N', 0x88, __u32)
#define NTSYNC_IOC_EVENT_RESET _IOR ('N', 0x89, __u32)
+#define NTSYNC_IOC_EVENT_PULSE _IOR ('N', 0x8a, __u32)
#endif
--
2.43.0
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