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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 25 Aug 2022 18:41:30 +0200
Subject: [PATCH 7/8] flex_proportions: Disable preemption entering the write
section.
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.0/older/patches-6.0.5-rt14.tar.xz
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>
Link: https://lore.kernel.org/r/20220825164131.402717-8-bigeasy@linutronix.de
---
lib/flex_proportions.c | 2 ++
1 file changed, 2 insertions(+)
--- a/lib/flex_proportions.c
+++ b/lib/flex_proportions.c
@@ -70,6 +70,7 @@ bool fprop_new_period(struct fprop_globa
*/
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_globa
percpu_counter_add(&p->events, -events);
p->period += periods;
write_seqcount_end(&p->sequence);
+ preempt_enable_nested();
return true;
}
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