* [PATCH] hazptrtorture: Fix inverted sleep condition in do_pending kthread
@ 2026-08-04 0:03 Bradley Morgan
2026-08-04 3:46 ` Paul E. McKenney
2026-09-04 13:01 ` Mathieu Desnoyers
0 siblings, 2 replies; 6+ messages in thread
From: Bradley Morgan @ 2026-08-04 0:03 UTC (permalink / raw)
To: Paul E . McKenney, Frederic Weisbecker, Neeraj Upadhyay,
Joel Fernandes, Josh Triplett, Boqun Feng, Uladzislau Rezki
Cc: Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, Zqiang, rcu,
linux-kernel
The do_pending kthread never sleeps. Its supposed to.
kthread_do_pending_ms sets the gap between cleanups, and the docs
say so too. But the sleep sits behind torture_must_stop(), and thats
false while the test runs. So the kthread never sleeps. It just loops.
It drains the pending lists over and over, no pause, and burns a full
CPU for the whole test.
Flip the check. With !torture_must_stop() it sleeps for
kthread_do_pending_ms between passes. When the test stops it does one
last cleanup and exits. Nothing left to do, so no sleep needed then.
Fixes: 94d2e93c222e ("hazptrtorture: Add kthread to release deferred hazard pointers")
Signed-off-by: Bradley Morgan <include@grrlz.net>
---
kernel/rcu/hazptrtorture.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/hazptrtorture.c b/kernel/rcu/hazptrtorture.c
index 72aeb50668e9..7c8b5899fb01 100644
--- a/kernel/rcu/hazptrtorture.c
+++ b/kernel/rcu/hazptrtorture.c
@@ -555,7 +555,7 @@ static int hazptr_torture_do_pending(void *arg)
cpu = cpumask_next_wrap(cpu, cpu_possible_mask);
hazptr_torture_do_one_pending(cpu, &rand);
}
- if (torture_must_stop())
+ if (!torture_must_stop())
torture_hrtimeout_ms(kthread_do_pending_ms, USEC_PER_MSEC, &rand);
// Omit stutter_wait() because this function needs to do cleanup.
} while (!torture_must_stop());
--
2.47.3
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] hazptrtorture: Fix inverted sleep condition in do_pending kthread
2026-08-04 0:03 [PATCH] hazptrtorture: Fix inverted sleep condition in do_pending kthread Bradley Morgan
@ 2026-08-04 3:46 ` Paul E. McKenney
2026-09-04 13:01 ` Mathieu Desnoyers
1 sibling, 0 replies; 6+ messages in thread
From: Paul E. McKenney @ 2026-08-04 3:46 UTC (permalink / raw)
To: Bradley Morgan
Cc: Frederic Weisbecker, Neeraj Upadhyay, Joel Fernandes,
Josh Triplett, Boqun Feng, Uladzislau Rezki, Steven Rostedt,
Mathieu Desnoyers, Lai Jiangshan, Zqiang, rcu, linux-kernel
On Tue, Aug 04, 2026 at 12:03:39AM +0000, Bradley Morgan wrote:
> The do_pending kthread never sleeps. Its supposed to.
> kthread_do_pending_ms sets the gap between cleanups, and the docs
> say so too. But the sleep sits behind torture_must_stop(), and thats
> false while the test runs. So the kthread never sleeps. It just loops.
> It drains the pending lists over and over, no pause, and burns a full
> CPU for the whole test.
>
> Flip the check. With !torture_must_stop() it sleeps for
> kthread_do_pending_ms between passes. When the test stops it does one
> last cleanup and exits. Nothing left to do, so no sleep needed then.
>
> Fixes: 94d2e93c222e ("hazptrtorture: Add kthread to release deferred hazard pointers")
> Signed-off-by: Bradley Morgan <include@grrlz.net>
Good catch, applied, thank you!
Thanx, Paul
> ---
> kernel/rcu/hazptrtorture.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/hazptrtorture.c b/kernel/rcu/hazptrtorture.c
> index 72aeb50668e9..7c8b5899fb01 100644
> --- a/kernel/rcu/hazptrtorture.c
> +++ b/kernel/rcu/hazptrtorture.c
> @@ -555,7 +555,7 @@ static int hazptr_torture_do_pending(void *arg)
> cpu = cpumask_next_wrap(cpu, cpu_possible_mask);
> hazptr_torture_do_one_pending(cpu, &rand);
> }
> - if (torture_must_stop())
> + if (!torture_must_stop())
> torture_hrtimeout_ms(kthread_do_pending_ms, USEC_PER_MSEC, &rand);
> // Omit stutter_wait() because this function needs to do cleanup.
> } while (!torture_must_stop());
> --
> 2.47.3
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] hazptrtorture: Fix inverted sleep condition in do_pending kthread
2026-08-04 0:03 [PATCH] hazptrtorture: Fix inverted sleep condition in do_pending kthread Bradley Morgan
2026-08-04 3:46 ` Paul E. McKenney
@ 2026-09-04 13:01 ` Mathieu Desnoyers
2026-09-04 16:00 ` Paul E. McKenney
1 sibling, 1 reply; 6+ messages in thread
From: Mathieu Desnoyers @ 2026-09-04 13:01 UTC (permalink / raw)
To: Bradley Morgan, Paul E . McKenney, Frederic Weisbecker,
Neeraj Upadhyay, Joel Fernandes, Josh Triplett, Boqun Feng,
Uladzislau Rezki
Cc: Steven Rostedt, Lai Jiangshan, Zqiang, rcu, linux-kernel
On 2026-08-03 20:03, Bradley Morgan wrote:
> The do_pending kthread never sleeps. Its supposed to.
> kthread_do_pending_ms sets the gap between cleanups, and the docs
> say so too. But the sleep sits behind torture_must_stop(), and thats
> false while the test runs. So the kthread never sleeps. It just loops.
> It drains the pending lists over and over, no pause, and burns a full
> CPU for the whole test.
Paul, I just found this patch in my junk email folder. Maybe relevant
for you ?
Thanks,
Mathieu
>
> Flip the check. With !torture_must_stop() it sleeps for
> kthread_do_pending_ms between passes. When the test stops it does one
> last cleanup and exits. Nothing left to do, so no sleep needed then.
>
> Fixes: 94d2e93c222e ("hazptrtorture: Add kthread to release deferred hazard pointers")
> Signed-off-by: Bradley Morgan <include@grrlz.net>
> ---
> kernel/rcu/hazptrtorture.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/hazptrtorture.c b/kernel/rcu/hazptrtorture.c
> index 72aeb50668e9..7c8b5899fb01 100644
> --- a/kernel/rcu/hazptrtorture.c
> +++ b/kernel/rcu/hazptrtorture.c
> @@ -555,7 +555,7 @@ static int hazptr_torture_do_pending(void *arg)
> cpu = cpumask_next_wrap(cpu, cpu_possible_mask);
> hazptr_torture_do_one_pending(cpu, &rand);
> }
> - if (torture_must_stop())
> + if (!torture_must_stop())
> torture_hrtimeout_ms(kthread_do_pending_ms, USEC_PER_MSEC, &rand);
> // Omit stutter_wait() because this function needs to do cleanup.
> } while (!torture_must_stop());
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] hazptrtorture: Fix inverted sleep condition in do_pending kthread
2026-09-04 13:01 ` Mathieu Desnoyers
@ 2026-09-04 16:00 ` Paul E. McKenney
2026-09-04 17:28 ` Bradley Morgan
0 siblings, 1 reply; 6+ messages in thread
From: Paul E. McKenney @ 2026-09-04 16:00 UTC (permalink / raw)
To: Mathieu Desnoyers
Cc: Bradley Morgan, Frederic Weisbecker, Neeraj Upadhyay,
Joel Fernandes, Josh Triplett, Boqun Feng, Uladzislau Rezki,
Steven Rostedt, Lai Jiangshan, Zqiang, rcu, linux-kernel
On Fri, Sep 04, 2026 at 09:01:05AM -0400, Mathieu Desnoyers wrote:
> On 2026-08-03 20:03, Bradley Morgan wrote:
> > The do_pending kthread never sleeps. Its supposed to.
> > kthread_do_pending_ms sets the gap between cleanups, and the docs
> > say so too. But the sleep sits behind torture_must_stop(), and thats
> > false while the test runs. So the kthread never sleeps. It just loops.
> > It drains the pending lists over and over, no pause, and burns a full
> > CPU for the whole test.
>
> Paul, I just found this patch in my junk email folder. Maybe relevant
> for you ?
We got it in my -rcu tree:
15b9fca2f5ce ("hazptrtorture: Fix inverted sleep condition in do_pending kthread")
But I do appreciate your checking for missed patches, thank you!
Thanx, Paul
> Thanks,
>
> Mathieu
>
> >
> > Flip the check. With !torture_must_stop() it sleeps for
> > kthread_do_pending_ms between passes. When the test stops it does one
> > last cleanup and exits. Nothing left to do, so no sleep needed then.
> >
> > Fixes: 94d2e93c222e ("hazptrtorture: Add kthread to release deferred hazard pointers")
> > Signed-off-by: Bradley Morgan <include@grrlz.net>
> > ---
> > kernel/rcu/hazptrtorture.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/rcu/hazptrtorture.c b/kernel/rcu/hazptrtorture.c
> > index 72aeb50668e9..7c8b5899fb01 100644
> > --- a/kernel/rcu/hazptrtorture.c
> > +++ b/kernel/rcu/hazptrtorture.c
> > @@ -555,7 +555,7 @@ static int hazptr_torture_do_pending(void *arg)
> > cpu = cpumask_next_wrap(cpu, cpu_possible_mask);
> > hazptr_torture_do_one_pending(cpu, &rand);
> > }
> > - if (torture_must_stop())
> > + if (!torture_must_stop())
> > torture_hrtimeout_ms(kthread_do_pending_ms, USEC_PER_MSEC, &rand);
> > // Omit stutter_wait() because this function needs to do cleanup.
> > } while (!torture_must_stop());
>
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> https://www.efficios.com
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] hazptrtorture: Fix inverted sleep condition in do_pending kthread
2026-09-04 16:00 ` Paul E. McKenney
@ 2026-09-04 17:28 ` Bradley Morgan
2026-09-05 20:40 ` Paul E. McKenney
0 siblings, 1 reply; 6+ messages in thread
From: Bradley Morgan @ 2026-09-04 17:28 UTC (permalink / raw)
To: paulmck
Cc: boqun, frederic, include, jiangshanlai, joelagnelf, josh,
linux-kernel, mathieu.desnoyers, neeraj.upadhyay, qiang.zhang,
rcu, rostedt, urezki
On 4 September 2026 17:00:22 BST, "Paul E. McKenney" <paulmck@kernel.org>
wrote:
>On Fri, Sep 04, 2026 at 09:01:05AM -0400, Mathieu Desnoyers wrote:
>> On 2026-08-03 20:03, Bradley Morgan wrote:
>> > The do_pending kthread never sleeps. Its supposed to.
>> > kthread_do_pending_ms sets the gap between cleanups, and the docs
>> > say so too. But the sleep sits behind torture_must_stop(), and thats
>> > false while the test runs. So the kthread never sleeps. It just loops.
>> > It drains the pending lists over and over, no pause, and burns a full
>> > CPU for the whole test.
>>
>> Paul, I just found this patch in my junk email folder. Maybe relevant
>> for you ?
>
>We got it in my -rcu tree:
>
>15b9fca2f5ce ("hazptrtorture: Fix inverted sleep condition in do_pending
>kthread")
>
>But I do appreciate your checking for missed patches, thank you!
>
> Thanx, Paul
>
>> Thanks,
>>
>> Mathieu
>>
>> >
>> > Flip the check. With !torture_must_stop() it sleeps for
>> > kthread_do_pending_ms between passes. When the test stops it does one
>> > last cleanup and exits. Nothing left to do, so no sleep needed then.
>> >
>> > Fixes: 94d2e93c222e ("hazptrtorture: Add kthread to release deferred
>hazard pointers")
>> > Signed-off-by: Bradley Morgan <include@grrlz.net>
>> > ---
>> > kernel/rcu/hazptrtorture.c | 2 +-
>> > 1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/kernel/rcu/hazptrtorture.c b/kernel/rcu/hazptrtorture.c
>> > index 72aeb50668e9..7c8b5899fb01 100644
>> > --- a/kernel/rcu/hazptrtorture.c
>> > +++ b/kernel/rcu/hazptrtorture.c
>> > @@ -555,7 +555,7 @@ static int hazptr_torture_do_pending(void *arg)
>> > cpu = cpumask_next_wrap(cpu, cpu_possible_mask);
>> > hazptr_torture_do_one_pending(cpu, &rand);
>> > }
>> > - if (torture_must_stop())
>> > + if (!torture_must_stop())
>> > torture_hrtimeout_ms(kthread_do_pending_ms, USEC_PER_MSEC, &rand);
>> > // Omit stutter_wait() because this function needs to do cleanup.
>> > } while (!torture_must_stop());
>>
>>
>> --
>> Mathieu Desnoyers
>> EfficiOS Inc.
>> https://www.efficios.com
>
>
Hi, new email.
Could I ask where the heck hazptr is? Its not in next, would you like,
help???
--- Thanks!
https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@grrlz.net/
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] hazptrtorture: Fix inverted sleep condition in do_pending kthread
2026-09-04 17:28 ` Bradley Morgan
@ 2026-09-05 20:40 ` Paul E. McKenney
0 siblings, 0 replies; 6+ messages in thread
From: Paul E. McKenney @ 2026-09-05 20:40 UTC (permalink / raw)
To: Bradley Morgan
Cc: boqun, frederic, include, jiangshanlai, joelagnelf, josh,
linux-kernel, mathieu.desnoyers, neeraj.upadhyay, qiang.zhang,
rcu, rostedt, urezki
On Fri, Sep 04, 2026 at 06:28:45PM +0100, Bradley Morgan wrote:
> On 4 September 2026 17:00:22 BST, "Paul E. McKenney" <paulmck@kernel.org>
> wrote:
> >On Fri, Sep 04, 2026 at 09:01:05AM -0400, Mathieu Desnoyers wrote:
> >> On 2026-08-03 20:03, Bradley Morgan wrote:
> >> > The do_pending kthread never sleeps. Its supposed to.
> >> > kthread_do_pending_ms sets the gap between cleanups, and the docs
> >> > say so too. But the sleep sits behind torture_must_stop(), and thats
> >> > false while the test runs. So the kthread never sleeps. It just loops.
> >> > It drains the pending lists over and over, no pause, and burns a full
> >> > CPU for the whole test.
> >>
> >> Paul, I just found this patch in my junk email folder. Maybe relevant
> >> for you ?
> >
> >We got it in my -rcu tree:
> >
> >15b9fca2f5ce ("hazptrtorture: Fix inverted sleep condition in do_pending
> >kthread")
> >
> >But I do appreciate your checking for missed patches, thank you!
> >
> > Thanx, Paul
> >
> >> Thanks,
> >>
> >> Mathieu
> >>
> >> >
> >> > Flip the check. With !torture_must_stop() it sleeps for
> >> > kthread_do_pending_ms between passes. When the test stops it does one
> >> > last cleanup and exits. Nothing left to do, so no sleep needed then.
> >> >
> >> > Fixes: 94d2e93c222e ("hazptrtorture: Add kthread to release deferred
> >hazard pointers")
> >> > Signed-off-by: Bradley Morgan <include@grrlz.net>
> >> > ---
> >> > kernel/rcu/hazptrtorture.c | 2 +-
> >> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >> >
> >> > diff --git a/kernel/rcu/hazptrtorture.c b/kernel/rcu/hazptrtorture.c
> >> > index 72aeb50668e9..7c8b5899fb01 100644
> >> > --- a/kernel/rcu/hazptrtorture.c
> >> > +++ b/kernel/rcu/hazptrtorture.c
> >> > @@ -555,7 +555,7 @@ static int hazptr_torture_do_pending(void *arg)
> >> > cpu = cpumask_next_wrap(cpu, cpu_possible_mask);
> >> > hazptr_torture_do_one_pending(cpu, &rand);
> >> > }
> >> > - if (torture_must_stop())
> >> > + if (!torture_must_stop())
> >> > torture_hrtimeout_ms(kthread_do_pending_ms, USEC_PER_MSEC, &rand);
> >> > // Omit stutter_wait() because this function needs to do cleanup.
> >> > } while (!torture_must_stop());
> >>
> >>
> >> --
> >> Mathieu Desnoyers
> >> EfficiOS Inc.
> >> https://www.efficios.com
> >
> >
> Hi, new email.
>
> Could I ask where the heck hazptr is? Its not in next, would you like,
> help???
>
> --- Thanks!
> https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@grrlz.net/
It is still in my -rcu tree.
I would not say "no" to a fix for this issue:
https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@grrlz.net/
Once that is in place, I would be happy to put this back into -next.
At some point, we will need to get rid of the concept of wildcard hazard
pointers, as those end up instead emulating RCU, but I don't see that
as an immediate obstacle.
Thanx, Paul
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2026-09-05 20:40 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2026-08-04 0:03 [PATCH] hazptrtorture: Fix inverted sleep condition in do_pending kthread Bradley Morgan
2026-08-04 3:46 ` Paul E. McKenney
2026-09-04 13:01 ` Mathieu Desnoyers
2026-09-04 16:00 ` Paul E. McKenney
2026-09-04 17:28 ` Bradley Morgan
2026-09-05 20:40 ` Paul E. McKenney
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