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flex_proportions: Disable preemption entering the write section.

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The seqcount fprop_global::sequence is not associated with a lock. The
write section (fprop_new_period()) is invoked from a timer and since the
softirq is preemptible on PREEMPT_RT it is possible to preempt the write
section which is not desited.

Disable preemption around the write section on PREEMPT_RT.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20220825164131.402717-8-bigeasy@linutronix.de
This commit is contained in:
Sebastian Andrzej Siewior 2022-08-25 18:41:30 +02:00 committed by Thomas Gleixner
parent c7e0b3d088
commit 9458e0a78c
1 changed files with 2 additions and 0 deletions
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2
lib/flex_proportions.c
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@ -70,6 +70,7 @@ bool fprop_new_period(struct fprop_global *p, int periods)
*/
if (events <= 1)
return false;
preempt_disable_nested();
write_seqcount_begin(&p->sequence);
if (periods < 64)
events -= events >> periods;
@ -77,6 +78,7 @@ bool fprop_new_period(struct fprop_global *p, int periods)
percpu_counter_add(&p->events, -events);
p->period += periods;
write_seqcount_end(&p->sequence);
preempt_enable_nested();
return true;
}