2022-03-25 11:34:56

by Zqiang

Subject: [PATCH] rcu: Check the validity of the boost_kthread_task pointer

The boost kthreads may spawn failed, although the probability of
creation failure is very low, in consideration of the robustness
of the code, add boost_kthread_task pointer detection.

Signed-off-by: Zqiang <[email protected]>
---
kernel/rcu/tree_plugin.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 6b9bcd45c7b2..fd642f14f31f 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1125,7 +1125,8 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
__releases(rnp->lock)
{
raw_lockdep_assert_held_rcu_node(rnp);
- if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) {
+ if (!rnp->boost_kthread_task ||
+ (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL)) {
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return;
}
--
2.25.1

2022-03-25 19:22:10

by Paul E. McKenney

Subject: Re: [PATCH] rcu: Check the validity of the boost_kthread_task pointer

On Thu, Mar 24, 2022 at 07:15:15PM +0800, Zqiang wrote:
> The boost kthreads may spawn failed, although the probability of
> creation failure is very low, in consideration of the robustness
> of the code, add boost_kthread_task pointer detection.
>
> Signed-off-by: Zqiang <[email protected]>

Good catch! As you say, rare, but definitely worth fixing.

I could not resist a bit of wordsmithing. Could you please check
to see if I messed something up?

Thanx, Paul

------------------------------------------------------------------------

commit ad3c438e248cbc41fe30a41287621c3dbfcdf51c
Author: Zqiang <[email protected]>
Date: Thu Mar 24 19:15:15 2022 +0800

rcu: Check for successful spawn of ->boost_kthread_task

For the spawning of the priority-boost kthreads can fail, improbable
though this might seem. This commit therefore refrains from attemoting
to initiate RCU priority boosting when The ->boost_kthread_task pointer
is NULL.

Signed-off-by: Zqiang <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 6b9bcd45c7b2..d58f6d6073bf 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1125,7 +1125,8 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
__releases(rnp->lock)
{
raw_lockdep_assert_held_rcu_node(rnp);
- if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) {
+ if (!rnp->boost_kthread_task ||
+ (!rcu_preempt_blocked_readers_cgp(rnp) && !rnp->exp_tasks)) {
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return;
}

2022-03-25 19:51:56

by Zqiang

Subject: RE: [PATCH] rcu: Check the validity of the boost_kthread_task pointer

On Thu, Mar 24, 2022 at 07:15:15PM +0800, Zqiang wrote:
> The boost kthreads may spawn failed, although the probability of
> creation failure is very low, in consideration of the robustness of
> the code, add boost_kthread_task pointer detection.
>
> Signed-off-by: Zqiang <[email protected]>
>
>Good catch! As you say, rare, but definitely worth fixing.
>
>I could not resist a bit of wordsmithing. Could you please check to see if I messed something up?

Thanks wordsmithing, I think it's ok.

Thanks,
Zqiang

>
> Thanx, Paul
>
>------------------------------------------------------------------------
>
>commit ad3c438e248cbc41fe30a41287621c3dbfcdf51c
>Author: Zqiang <[email protected]>
>Date: Thu Mar 24 19:15:15 2022 +0800
>
> rcu: Check for successful spawn of ->boost_kthread_task
>
> For the spawning of the priority-boost kthreads can fail, improbable
> though this might seem. This commit therefore refrains from attemoting
> to initiate RCU priority boosting when The ->boost_kthread_task pointer
> is NULL.
>
> Signed-off-by: Zqiang <[email protected]>
> Signed-off-by: Paul E. McKenney <[email protected]>
>
>diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 6b9bcd45c7b2..d58f6d6073bf 100644
>--- a/kernel/rcu/tree_plugin.h
>+++ b/kernel/rcu/tree_plugin.h
>@@ -1125,7 +1125,8 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
> __releases(rnp->lock)
> {
> raw_lockdep_assert_held_rcu_node(rnp);
>- if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) {
>+ if (!rnp->boost_kthread_task ||
>+ (!rcu_preempt_blocked_readers_cgp(rnp) && !rnp->exp_tasks)) {
> raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
> return;
> }