Commit 9458e0a7 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Thomas Gleixner
Browse files

flex_proportions: Disable preemption entering the write section. 



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: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20220825164131.402717-8-bigeasy@linutronix.de
parent c7e0b3d0

lib/flex_proportions.c

+2 −0
Original line number Diff line number Diff line
@@ -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;

}