* [PATCH] rcu/srcutiny: don't return before reenabling preemption
@ 2024-10-07 10:14 Michal Schmidt
2024-10-09 17:19 ` Paul E. McKenney
0 siblings, 1 reply; 3+ messages in thread
From: Michal Schmidt @ 2024-10-07 10:14 UTC (permalink / raw)
To: Lai Jiangshan, Paul E. McKenney, Josh Triplett, Steven Rostedt,
Mathieu Desnoyers, Uladzislau Rezki (Sony)
Cc: rcu, linux-kernel
Code after the return statement is dead. Enable preemption before
returning from srcu_drive_gp().
This will be important when/if PREEMPT_AUTO (lazy resched) gets merged.
Fixes: 65b4a59557f6 ("srcu: Make Tiny SRCU explicitly disable preemption")
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
---
kernel/rcu/srcutiny.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
index 549c03336ee9..4dcbf8aa80ff 100644
--- a/kernel/rcu/srcutiny.c
+++ b/kernel/rcu/srcutiny.c
@@ -122,8 +122,8 @@ void srcu_drive_gp(struct work_struct *wp)
ssp = container_of(wp, struct srcu_struct, srcu_work);
preempt_disable(); // Needed for PREEMPT_AUTO
if (ssp->srcu_gp_running || ULONG_CMP_GE(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max))) {
- return; /* Already running or nothing to do. */
preempt_enable();
+ return; /* Already running or nothing to do. */
}
/* Remove recently arrived callbacks and wait for readers. */
--
2.46.2
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] rcu/srcutiny: don't return before reenabling preemption
2024-10-07 10:14 [PATCH] rcu/srcutiny: don't return before reenabling preemption Michal Schmidt
@ 2024-10-09 17:19 ` Paul E. McKenney
2024-10-18 21:10 ` Frederic Weisbecker
0 siblings, 1 reply; 3+ messages in thread
From: Paul E. McKenney @ 2024-10-09 17:19 UTC (permalink / raw)
To: Michal Schmidt
Cc: Lai Jiangshan, Josh Triplett, Steven Rostedt, Mathieu Desnoyers,
Uladzislau Rezki (Sony), rcu, linux-kernel
On Mon, Oct 07, 2024 at 12:14:15PM +0200, Michal Schmidt wrote:
> Code after the return statement is dead. Enable preemption before
> returning from srcu_drive_gp().
>
> This will be important when/if PREEMPT_AUTO (lazy resched) gets merged.
>
> Fixes: 65b4a59557f6 ("srcu: Make Tiny SRCU explicitly disable preemption")
> Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Good catch!
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
> ---
> kernel/rcu/srcutiny.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
> index 549c03336ee9..4dcbf8aa80ff 100644
> --- a/kernel/rcu/srcutiny.c
> +++ b/kernel/rcu/srcutiny.c
> @@ -122,8 +122,8 @@ void srcu_drive_gp(struct work_struct *wp)
> ssp = container_of(wp, struct srcu_struct, srcu_work);
> preempt_disable(); // Needed for PREEMPT_AUTO
> if (ssp->srcu_gp_running || ULONG_CMP_GE(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max))) {
> - return; /* Already running or nothing to do. */
> preempt_enable();
> + return; /* Already running or nothing to do. */
> }
>
> /* Remove recently arrived callbacks and wait for readers. */
> --
> 2.46.2
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] rcu/srcutiny: don't return before reenabling preemption
2024-10-09 17:19 ` Paul E. McKenney
@ 2024-10-18 21:10 ` Frederic Weisbecker
0 siblings, 0 replies; 3+ messages in thread
From: Frederic Weisbecker @ 2024-10-18 21:10 UTC (permalink / raw)
To: Paul E. McKenney
Cc: Michal Schmidt, Lai Jiangshan, Josh Triplett, Steven Rostedt,
Mathieu Desnoyers, Uladzislau Rezki (Sony), rcu, linux-kernel
Le Wed, Oct 09, 2024 at 10:19:01AM -0700, Paul E. McKenney a écrit :
> On Mon, Oct 07, 2024 at 12:14:15PM +0200, Michal Schmidt wrote:
> > Code after the return statement is dead. Enable preemption before
> > returning from srcu_drive_gp().
> >
> > This will be important when/if PREEMPT_AUTO (lazy resched) gets merged.
> >
> > Fixes: 65b4a59557f6 ("srcu: Make Tiny SRCU explicitly disable preemption")
> > Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
>
> Good catch!
>
> Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Applied!
Thanks.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2024-10-07 10:14 [PATCH] rcu/srcutiny: don't return before reenabling preemption Michal Schmidt
2024-10-09 17:19 ` Paul E. McKenney
2024-10-18 21:10 ` Frederic Weisbecker
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