[PATCH v2] kernel/locking: mutex: simplify access to the first entry in the wait-list

[PATCH v2] kernel/locking: mutex: simplify access to the first entry in the wait-list

[Andrzej Pietrasiewicz]

Use list_first_entry instead of explicitly accessing the first entry
with "head".next. The comment one line above becomes obsolete.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---

v1..v2:

- corrected the email address in the second Signed-off-by line

 kernel/locking/mutex.c |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 4dd6e4c..4af4f9c 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -730,10 +730,9 @@ __mutex_unlock_common_slowpath(atomic_t *lock_count, int nested)
 		atomic_set(&lock->count, 1);
 
 	if (!list_empty(&lock->wait_list)) {
-		/* get the first entry from the wait-list: */
 		struct mutex_waiter *waiter =
-				list_entry(lock->wait_list.next,
-					   struct mutex_waiter, list);
+				list_first_entry(&lock->wait_list,
+						 struct mutex_waiter, list);
 
 		debug_mutex_wake_waiter(lock, waiter);
 
-- 
1.7.0.4

Re: [PATCH v2] kernel/locking: mutex: simplify access to the first entry in the wait-list

[Peter Zijlstra]

On Thu, Dec 12, 2013 at 12:29:32PM +0100, Andrzej Pietrasiewicz wrote:
> Use list_first_entry instead of explicitly accessing the first entry
> with "head".next. The comment one line above becomes obsolete.
> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> ---
> 
> v1..v2:
> 
> - corrected the email address in the second Signed-off-by line

Still invalid; the problem is that you appear to have written the patch
(you send it and you have first sob).

So what is Kyungmin doing in the line? He did not send me your patch.

RE: [PATCH v2] kernel/locking: mutex: simplify access to the first entry in the wait-list

[Kyungmin Park]

> -----Original Message-----
> From: Peter Zijlstra [mailto:peterz@infradead.org]
> Sent: Thursday, December 12, 2013 8:35 PM
> To: Andrzej Pietrasiewicz
> Cc: linux-kernel@vger.kernel.org; Kyungmin Park; Marek Szyprowski; Ingo
> Molnar
> Subject: Re: [PATCH v2] kernel/locking: mutex: simplify access to the
> first entry in the wait-list
> 
> On Thu, Dec 12, 2013 at 12:29:32PM +0100, Andrzej Pietrasiewicz wrote:
> > Use list_first_entry instead of explicitly accessing the first entry
> > with "head".next. The comment one line above becomes obsolete.
> >
> > Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
> > Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> > ---
> >
> > v1..v2:
> >
> > - corrected the email address in the second Signed-off-by line
> 
> Still invalid; the problem is that you appear to have written the patch
> (you send it and you have first sob).


> So what is Kyungmin doing in the line? He did not send me your patch.

Internal review process, and it represents this patch comes from.

Thank you,
Kyungmin Park

Re: [PATCH v2] kernel/locking: mutex: simplify access to the first entry in the wait-list

[Ingo Molnar]

* Kyungmin Park <kyungmin.park@samsung.com> wrote:

> 
> > -----Original Message-----
> > From: Peter Zijlstra [mailto:peterz@infradead.org]
> > Sent: Thursday, December 12, 2013 8:35 PM
> > To: Andrzej Pietrasiewicz
> > Cc: linux-kernel@vger.kernel.org; Kyungmin Park; Marek Szyprowski; Ingo
> > Molnar
> > Subject: Re: [PATCH v2] kernel/locking: mutex: simplify access to the
> > first entry in the wait-list
> > 
> > On Thu, Dec 12, 2013 at 12:29:32PM +0100, Andrzej Pietrasiewicz wrote:
> > > Use list_first_entry instead of explicitly accessing the first entry
> > > with "head".next. The comment one line above becomes obsolete.
> > >
> > > Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
> > > Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> > > ---
> > >
> > > v1..v2:
> > >
> > > - corrected the email address in the second Signed-off-by line
> > 
> > Still invalid; the problem is that you appear to have written the patch
> > (you send it and you have first sob).
> 
> 
> > So what is Kyungmin doing in the line? He did not send me your patch.
> 
> Internal review process, and it represents this patch comes from.

That can be expressed via a Reviewed-by line.

Thanks,

	Ingo

Re: [PATCH v2] kernel/locking: mutex: simplify access to the first entry in the wait-list

[Peter Zijlstra]

On Thu, Dec 12, 2013 at 09:02:07PM +0900, Kyungmin Park wrote:
> 
> > -----Original Message-----
> > From: Peter Zijlstra [mailto:peterz@infradead.org]
> > Sent: Thursday, December 12, 2013 8:35 PM
> > To: Andrzej Pietrasiewicz
> > Cc: linux-kernel@vger.kernel.org; Kyungmin Park; Marek Szyprowski; Ingo
> > Molnar
> > Subject: Re: [PATCH v2] kernel/locking: mutex: simplify access to the
> > first entry in the wait-list
> > 
> > On Thu, Dec 12, 2013 at 12:29:32PM +0100, Andrzej Pietrasiewicz wrote:
> > > Use list_first_entry instead of explicitly accessing the first entry
> > > with "head".next. The comment one line above becomes obsolete.
> > >
> > > Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
> > > Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> > > ---
> > >
> > > v1..v2:
> > >
> > > - corrected the email address in the second Signed-off-by line
> > 
> > Still invalid; the problem is that you appear to have written the patch
> > (you send it and you have first sob).
> 
> 
> > So what is Kyungmin doing in the line? He did not send me your patch.
> 
> Internal review process, and it represents this patch comes from.

For review we have this specific tag, oddly called: 'Reviewed-by'.

Re: [PATCH v2] kernel/locking: mutex: simplify access to the first entry in the wait-list

[Andrzej Pietrasiewicz]

Hello Ingo & Peter,

I added Greg on Cc.

W dniu 12.12.2013 13:52, Peter Zijlstra pisze:
> On Thu, Dec 12, 2013 at 09:02:07PM +0900, Kyungmin Park wrote:
>>
>>> -----Original Message-----
>>> From: Peter Zijlstra [mailto:peterz@infradead.org]
>>> Sent: Thursday, December 12, 2013 8:35 PM
>>> To: Andrzej Pietrasiewicz
>>> Cc: linux-kernel@vger.kernel.org; Kyungmin Park; Marek Szyprowski; Ingo
>>> Molnar
>>> Subject: Re: [PATCH v2] kernel/locking: mutex: simplify access to the
>>> first entry in the wait-list
>>>
>>> On Thu, Dec 12, 2013 at 12:29:32PM +0100, Andrzej Pietrasiewicz wrote:
>>>> Use list_first_entry instead of explicitly accessing the first entry
>>>> with "head".next. The comment one line above becomes obsolete.
>>>>
>>>> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
>>>> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
>>>> ---

For quite a long time I've been sending the same SOB lines to the
linux-usb list.

Can you please refer here:

http://www.spinics.net/lists/linux-usb/msg74981.html


>>>>
>>>> v1..v2:
>>>>
>>>> - corrected the email address in the second Signed-off-by line
>>>
>>> Still invalid; the problem is that you appear to have written the patch
>>> (you send it and you have first sob).
>>
>>
>>> So what is Kyungmin doing in the line? He did not send me your patch.
>>
>> Internal review process, and it represents this patch comes from.
>
> For review we have this specific tag, oddly called: 'Reviewed-by'.
>

Re: [PATCH v2] kernel/locking: mutex: simplify access to the first entry in the wait-list

[Peter Zijlstra]

On Fri, Dec 13, 2013 at 07:24:06AM +0100, Andrzej Pietrasiewicz wrote:
> Hello Ingo & Peter,
> 
> I added Greg on Cc.

> For quite a long time I've been sending the same SOB lines to the
> linux-usb list.

Then Greg is more forgiving. Doesn't make it right though.

Re: [PATCH v2] kernel/locking: mutex: simplify access to the first entry in the wait-list

[Ingo Molnar]

* Andrzej Pietrasiewicz <andrzej.p@samsung.com> wrote:

> Hello Ingo & Peter,
> 
> I added Greg on Cc.
> 
> W dniu 12.12.2013 13:52, Peter Zijlstra pisze:
> >On Thu, Dec 12, 2013 at 09:02:07PM +0900, Kyungmin Park wrote:
> >>
> >>>-----Original Message-----
> >>>From: Peter Zijlstra [mailto:peterz@infradead.org]
> >>>Sent: Thursday, December 12, 2013 8:35 PM
> >>>To: Andrzej Pietrasiewicz
> >>>Cc: linux-kernel@vger.kernel.org; Kyungmin Park; Marek Szyprowski; Ingo
> >>>Molnar
> >>>Subject: Re: [PATCH v2] kernel/locking: mutex: simplify access to the
> >>>first entry in the wait-list
> >>>
> >>>On Thu, Dec 12, 2013 at 12:29:32PM +0100, Andrzej Pietrasiewicz wrote:
> >>>>Use list_first_entry instead of explicitly accessing the first entry
> >>>>with "head".next. The comment one line above becomes obsolete.
> >>>>
> >>>>Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
> >>>>Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> >>>>---
> 
> For quite a long time I've been sending the same SOB lines to the
> linux-usb list.

They can slip through the cracks - but in the past Linus has 
complained about such SOB sequences so it's a real concern.

SOB has a very specific purpose outlined in 
Documentation/SubmittingPatches, please use Reviewed-by or other 
methods of adding credit to others.

Of course if you write a patch and Kyungmin sends me the patch then 
that signoff sequence is completely valid.

Thanks,

	Ingo

Re: [PATCH v2] kernel/locking: mutex: simplify access to the first entry in the wait-list

[Ingo Molnar]

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Fri, Dec 13, 2013 at 07:24:06AM +0100, Andrzej Pietrasiewicz wrote:
> > Hello Ingo & Peter,
> > 
> > I added Greg on Cc.
> 
> > For quite a long time I've been sending the same SOB lines to the
> > linux-usb list.
> 
> Then Greg is more forgiving. Doesn't make it right though.

Also, it's easy to not notice, and it has no testable side effects.

Yet if mistakes _are_ noticed like in this case then the inconsistency 
should be fixed, as the SOB chains have specific meaning.

Thanks,

	Ingo

Re: [PATCH v2] kernel/locking: mutex: simplify access to the first entry in the wait-list

[Greg Kroah-Hartman]

On Fri, Dec 13, 2013 at 03:00:11PM +0100, Peter Zijlstra wrote:
> On Fri, Dec 13, 2013 at 07:24:06AM +0100, Andrzej Pietrasiewicz wrote:
> > Hello Ingo & Peter,
> > 
> > I added Greg on Cc.
> 
> > For quite a long time I've been sending the same SOB lines to the
> > linux-usb list.
> 
> Then Greg is more forgiving. Doesn't make it right though.

I usually make sure the one sending me the patch is the "last" on the
chain, if not, that's a mistake on my part when I take the patch, sorry.

greg k-h