Re: [PATCH RT 0/1] Linux v4.19.312-rt134-rc2
Hi Sebastian, On Tue, May 07, 2024 at 11:54:07AM GMT, Sebastian Andrzej Siewior wrote: > I compared mine outcome vs v4.19-rt-next and the diff at the bottom came > out: > > - timer_delete_sync() used to have "#if 0" block around > lockdep_assert_preemption_enabled() because the function is not part > of v4.19. You ended up with might_sleep() which is a minor change. > Your queue as of a previous release had the if0 block (in > __del_timer_sync()). > I would say this is minor but looks like a miss-merge. Therefore I > would say it should go back for consistency vs previous release and > not change it due to conflicts. Makes sense. > - The timer_delete_sync() is structured differently with > __del_timer_sync(). That function invokes timer_sync_wait_running() > which drops two locks which are not acquired. That is wrong. It should > have been del_timer_wait_running(). Understood. I was a bit strungling here. Glad you caught this error. > I suggest you apply the diff below to align it with later versions. It > also gets rid of the basep argument in __try_to_del_timer_sync() which > is not really used. Will do. > As an alternative I can send you my rebased queue if this makes it > easier for you. Yes please, this makes it easy to sync the rebase branch. Thanks a lot! Cheers, Daniel
Re: [PATCH RT 0/1] Linux v4.19.312-rt134-rc2
On 2024-05-06 13:00:39 [+0200], Daniel Wagner wrote:
> Hi Sebastian,
Hi Daniel,
> On 06.05.24 12:46, Daniel Wagner wrote:
> > Dear RT Folks,
> >
> > This is the RT stable review cycle of patch 4.19.312-rt134-rc2.
> >
> > Please scream at me if I messed something up. Please test the patches
> > too.
>
> My announce script is not attaching any conflict resolve diffs
> (eventually, I'll fix this). Could have a look if I got the
> kernel/time/timer.c upddate right? This was caused by stable
> including the 030dcdd197d7 ("timers: Prepare support for
> PREEMPT_RT") patch.
I compared mine outcome vs v4.19-rt-next and the diff at the bottom came
out:
- timer_delete_sync() used to have "#if 0" block around
lockdep_assert_preemption_enabled() because the function is not part
of v4.19. You ended up with might_sleep() which is a minor change.
Your queue as of a previous release had the if0 block (in
__del_timer_sync()).
I would say this is minor but looks like a miss-merge. Therefore I
would say it should go back for consistency vs previous release and
not change it due to conflicts.
- The timer_delete_sync() is structured differently with
__del_timer_sync(). That function invokes timer_sync_wait_running()
which drops two locks which are not acquired. That is wrong. It should
have been del_timer_wait_running().
I suggest you apply the diff below to align it with later versions. It
also gets rid of the basep argument in __try_to_del_timer_sync() which
is not really used.
As an alternative I can send you my rebased queue if this makes it
easier for you.
Sebastian
-->8-
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1250,25 +1250,6 @@ int del_timer(struct timer_list *timer)
}
EXPORT_SYMBOL(del_timer);
-static int __try_to_del_timer_sync(struct timer_list *timer,
- struct timer_base **basep)
-{
- struct timer_base *base;
- unsigned long flags;
- int ret = -1;
-
- debug_assert_init(timer);
-
- *basep = base = lock_timer_base(timer, );
-
- if (base->running_timer != timer)
- ret = detach_if_pending(timer, base, true);
-
- raw_spin_unlock_irqrestore(>lock, flags);
-
- return ret;
-}
-
/**
* try_to_del_timer_sync - Try to deactivate a timer
* @timer: Timer to deactivate
@@ -1288,8 +1269,19 @@ static int __try_to_del_timer_sync(struct timer_list
*timer,
int try_to_del_timer_sync(struct timer_list *timer)
{
struct timer_base *base;
+ unsigned long flags;
+ int ret = -1;
- return __try_to_del_timer_sync(timer, );
+ debug_assert_init(timer);
+
+ base = lock_timer_base(timer, );
+
+ if (base->running_timer != timer)
+ ret = detach_if_pending(timer, base, true);
+
+ raw_spin_unlock_irqrestore(>lock, flags);
+
+ return ret;
}
EXPORT_SYMBOL(try_to_del_timer_sync);
@@ -1366,36 +1358,6 @@ static inline void timer_sync_wait_running(struct
timer_base *base) { }
static inline void del_timer_wait_running(struct timer_list *timer) { }
#endif
-static int __del_timer_sync(struct timer_list *timer)
-{
- struct timer_base *base;
- int ret;
-
- /*
-* Must be able to sleep on PREEMPT_RT because of the slowpath in
-* del_timer_wait_running().
-*/
-#if 0
- if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(timer->flags & TIMER_IRQSAFE))
- lockdep_assert_preemption_enabled();
-#endif
-
- for (;;) {
- ret = __try_to_del_timer_sync(timer, );
- if (ret >= 0)
- return ret;
-
- if (READ_ONCE(timer->flags) & TIMER_IRQSAFE)
- continue;
-
- /*
-* When accessing the lock, timers of base are no longer expired
-* and so timer is no longer running.
-*/
- timer_sync_wait_running(base);
- }
-}
-
/**
* timer_delete_sync - Deactivate a timer and wait for the handler to finish.
* @timer: The timer to be deactivated
@@ -1437,6 +1399,8 @@ static int __del_timer_sync(struct timer_list *timer)
*/
int timer_delete_sync(struct timer_list *timer)
{
+ int ret;
+
#ifdef CONFIG_LOCKDEP
unsigned long flags;
@@ -1454,14 +1418,26 @@ int timer_delete_sync(struct timer_list *timer)
* could lead to deadlock.
*/
WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE));
+
/*
* Must be able to sleep on PREEMPT_RT because of the slowpath in
-* __del_timer_sync().
+* del_timer_wait_running().
*/
+#if 0
if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(timer->flags & TIMER_IRQSAFE))
- might_sleep();
+ lockdep_assert_preemption_enabled();
+#endif
- return __del_timer_sync(timer);
+ do {
+ ret =
Re: [PATCH RT 0/1] Linux v4.19.312-rt134-rc2
Hi Sebastian,
On 06.05.24 12:46, Daniel Wagner wrote:
Dear RT Folks,
This is the RT stable review cycle of patch 4.19.312-rt134-rc2.
Please scream at me if I messed something up. Please test the patches
too.
My announce script is not attaching any conflict resolve diffs
(eventually, I'll fix this). Could have a look if I got the
kernel/time/timer.c upddate right? This was caused by stable
including the 030dcdd197d7 ("timers: Prepare support for
PREEMPT_RT") patch.
commit 2c1a32c5e05fd75885186793bc0d26e0a65b473d
Merge: 4790d0210f19 3d86e7f5bdf3
Author: Daniel Wagner
Date: Wed Apr 17 16:31:21 2024 +0200
Merge tag 'v4.19.312' into v4.19-rt-next
This is the 4.19.312 stable release
Conflicts:
include/linux/timer.h
kernel/time/timer.c
diff --git a/include/linux/timer.h b/include/linux/timer.h
remerge CONFLICT (content): Merge conflict in include/linux/timer.h
index b70c5168a346..aef40cac2add 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -173,13 +173,6 @@ extern void add_timer(struct timer_list *timer);
extern int try_to_del_timer_sync(struct timer_list *timer);
extern int timer_delete_sync(struct timer_list *timer);
-<<< 4790d0210f19 (Linux 4.19.307-rt133)
-#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT_FULL)
- extern int del_timer_sync(struct timer_list *timer);
-#else
-# define del_timer_sync(t) del_timer(t)
-#endif
-===
/**
* del_timer_sync - Delete a pending timer and wait for a running callback
* @timer: The timer to be deleted
@@ -192,7 +185,6 @@ static inline int del_timer_sync(struct timer_list
*timer)
{
return timer_delete_sync(timer);
}
->>> 3d86e7f5bdf3 (Linux 4.19.312)
#define del_singleshot_timer_sync(t) del_timer_sync(t)
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
remerge CONFLICT (content): Merge conflict in kernel/time/timer.c
index 911191916df1..bc5ce0cf9488 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1250,6 +1250,25 @@ int del_timer(struct timer_list *timer)
}
EXPORT_SYMBOL(del_timer);
+static int __try_to_del_timer_sync(struct timer_list *timer,
+ struct timer_base **basep)
+{
+ struct timer_base *base;
+ unsigned long flags;
+ int ret = -1;
+
+ debug_assert_init(timer);
+
+ *basep = base = lock_timer_base(timer, );
+
+ if (base->running_timer != timer)
+ ret = detach_if_pending(timer, base, true);
+
+ raw_spin_unlock_irqrestore(>lock, flags);
+
+ return ret;
+}
+
/**
* try_to_del_timer_sync - Try to deactivate a timer
* @timer: Timer to deactivate
@@ -1269,19 +1288,8 @@ EXPORT_SYMBOL(del_timer);
int try_to_del_timer_sync(struct timer_list *timer)
{
struct timer_base *base;
- unsigned long flags;
- int ret = -1;
-
- debug_assert_init(timer);
-
- base = lock_timer_base(timer, );
-
- if (base->running_timer != timer)
- ret = detach_if_pending(timer, base, true);
-
- raw_spin_unlock_irqrestore(>lock, flags);
- return ret;
+ return __try_to_del_timer_sync(timer, );
}
EXPORT_SYMBOL(try_to_del_timer_sync);
@@ -1303,7 +1311,6 @@ static inline void timer_base_unlock_expiry(struct
timer_base *base)
/*
* The counterpart to del_timer_wait_running().
-<<< 4790d0210f19 (Linux 4.19.307-rt133)
*
* If there is a waiter for base->expiry_lock, then it was waiting for the
* timer callback to finish. Drop expiry_lock and reaquire it. That allows
@@ -1359,64 +1366,35 @@ static inline void
timer_sync_wait_running(struct timer_base *base) { }
static inline void del_timer_wait_running(struct timer_list *timer) { }
#endif
-#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT_FULL)
-/**
- * del_timer_sync - deactivate a timer and wait for the handler to finish.
- * @timer: the timer to be deactivated
-===
->>> 3d86e7f5bdf3 (Linux 4.19.312)
- *
- * If there is a waiter for base->expiry_lock, then it was waiting for the
- * timer callback to finish. Drop expiry_lock and reaquire it. That allows
- * the waiter to acquire the lock and make progress.
- */
-static void timer_sync_wait_running(struct timer_base *base)
+static int __del_timer_sync(struct timer_list *timer)
{
- if (atomic_read(>timer_waiters)) {
- spin_unlock(>expiry_lock);
- spin_lock(>expiry_lock);
- }
-}
+ struct timer_base *base;
+ int ret;
-/*
- * This function is called on PREEMPT_RT kernels when the fast path
- * deletion of a timer failed because the timer callback function was
- * running.
- *
- * This prevents priority inversion, if the softirq thread on a remote CPU
- * got preempted, and it prevents a life lock when the task which tries to
- * delete a timer preempted the softirq thread running the timer callback
- * function.
- */
-static void del_timer_wait_running(struct timer_list *timer)
-{
- u32 tf;
+ /*
+
[PATCH RT 0/1] Linux v4.19.312-rt134-rc2
Dear RT Folks, This is the RT stable review cycle of patch 4.19.312-rt134-rc2. Please scream at me if I messed something up. Please test the patches too. The -rc release is also available on kernel.org https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git on the v4.19-rt-next branch. If all goes well, this patch will be converted to the next main release on 2024-05-13. Signing key fingerprint: 5BF6 7BC5 0826 72CA BB45 ACAE 587C 5ECA 5D0A 306C All keys used for the above files and repositories can be found on the following git repository: git://git.kernel.org/pub/scm/docs/kernel/pgpkeys.git Enjoy! Daniel Changes from v4.19.307-rt133: Daniel Wagner (1): Linux 4.19.312-rt134 localversion-rt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.44.0
