* Re: sched: exporting linux-rt migrate_disable for ZFS
2020-12-14 12:33 ` Sebastian Andrzej Siewior
@ 2020-12-14 23:31 ` Orivej Desh
2020-12-15 3:19 ` Mike Galbraith
1 sibling, 0 replies; 5+ messages in thread
From: Orivej Desh @ 2020-12-14 23:31 UTC (permalink / raw)
To: Sebastian Andrzej Siewior
Cc: LKML, Thomas Gleixner, Steven Rostedt, linux-rt-users,
Peter Zijlstra, Brian Behlendorf
* Sebastian Andrzej Siewior <bigeasy@linutronix.de> [2020-12-14]
> On 2020-12-08 23:58:27 [+0000], Orivej Desh wrote:
> > With sched-Add-migrate_disable.patch first released in v5.9-rc8-rt14 [1]
> > linux-rt defines functions migrate_disable and migrate_enable.
> > They are used in linux headers in various macros and static inline
> > functions, and in particular in kmap_atomic and kunmap_atomic.
> > The latter are needed by ZFS which currently fails to build against
> > 5.9-rt [2] because these functions are exported with EXPORT_SYMBOL_GPL.
> > Could you export them with EXPORT_SYMBOL instead?
>
> This is out of my jurisdiction, so just a few notes:
> - v5.9 is out of maintenance. Be careful.
Thanks! I have noticed a bug with usb-storage (using smp_processor_id
in preemptible code) in 5.9.1-rt20 thas has been fixed in 5.10-rt17.
> - We don't export symbols for out-of-tree modules.
The issue is that in the vanilla kernel these two functions are
available as macros that expand into EXPORT_SYMBOL function calls
(kunmap_atomic_high, etc.). If I am not mistaken the kernel is
generally supposed to keep the API made available to non-GPL modules
still available, for example here https://lwn.net/Articles/171838/ :
"When GPL-only exports were first added to the kernel, they went in
with the understanding that only new symbols would be tagged
GPL-only. The current module interface - while always subject to
change - was not to have symbols withdrawn arbitrarily." The current
rt patch has this effect: it makes non-GPL API of the vanilla kernel
GPL-only.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: sched: exporting linux-rt migrate_disable for ZFS
2020-12-14 12:33 ` Sebastian Andrzej Siewior
2020-12-14 23:31 ` Orivej Desh
@ 2020-12-15 3:19 ` Mike Galbraith
2020-12-15 14:05 ` Steven Rostedt
1 sibling, 1 reply; 5+ messages in thread
From: Mike Galbraith @ 2020-12-15 3:19 UTC (permalink / raw)
To: Sebastian Andrzej Siewior, Orivej Desh
Cc: LKML, Thomas Gleixner, Steven Rostedt, linux-rt-users,
Peter Zijlstra, Brian Behlendorf
On Mon, 2020-12-14 at 13:33 +0100, Sebastian Andrzej Siewior wrote:
> On 2020-12-08 23:58:27 [+0000], Orivej Desh wrote:
> > Greetings!
> Hi,
>
> > With sched-Add-migrate_disable.patch first released in v5.9-rc8-rt14 [1]
> > linux-rt defines functions migrate_disable and migrate_enable.
> > They are used in linux headers in various macros and static inline
> > functions, and in particular in kmap_atomic and kunmap_atomic.
> > The latter are needed by ZFS which currently fails to build against
> > 5.9-rt [2] because these functions are exported with EXPORT_SYMBOL_GPL.
> > Could you export them with EXPORT_SYMBOL instead?
>
> This is out of my jurisdiction, so just a few notes:
> - v5.9 is out of maintenance. Be careful.
> - We don't export symbols for out-of-tree modules.
Hm, dejavu all over again. I recall this issue long ago having been
resolved in favor of exporting via plain EXPORT_SYMBOL.
https://lore.kernel.org/linux-rt-users/1321359802.4181.1.camel@frodo/
From 859a31c5ec958326dd046f4e41f6fa0db0ce98c3 Mon Sep 17 00:00:00 2001
From: Steven Rostedt <srostedt@redhat.com>
Date: Mon, 16 Apr 2012 21:51:54 -0400
Subject: rt: Make migrate_disable/enable() and __rt_mutex_init non-GPL only
Modules that load on the normal vanilla kernel should also load on
an -rt kernel as well. This does not mean we condone non-GPL modules,
we are only being consistent.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/rtmutex.c | 2 +-
kernel/sched.c | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index a02fbd9f9583..d58db993f5cd 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -1282,7 +1282,7 @@ void __rt_mutex_init(struct rt_mutex *lock, const char *name)
debug_rt_mutex_init(lock, name);
}
-EXPORT_SYMBOL_GPL(__rt_mutex_init);
+EXPORT_SYMBOL(__rt_mutex_init);
/**
* rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a
diff --git a/kernel/sched.c b/kernel/sched.c
index df3048139d1b..ed3433573641 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4255,7 +4255,7 @@ void migrate_disable(void)
p->migrate_disable = 1;
preempt_enable();
}
-EXPORT_SYMBOL_GPL(migrate_disable);
+EXPORT_SYMBOL(migrate_disable);
void migrate_enable(void)
{
@@ -4307,7 +4307,7 @@ void migrate_enable(void)
unpin_current_cpu();
preempt_enable();
}
-EXPORT_SYMBOL_GPL(migrate_enable);
+EXPORT_SYMBOL(migrate_enable);
#else
static inline void update_migrate_disable(struct task_struct *p) { }
#define migrate_disabled_updated(p) 0
--
2.29.2
^ permalink raw reply related [flat|nested] 5+ messages in thread