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include/linux/percpu_counter.h: race in uniprocessor percpu_counter_add()

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The percpu interface is supposed to be preempt and irq safe.

But:
The uniprocessor implementation of percpu_counter_add() is not irq safe:
if an interrupt happens during the +=, then the result is undefined.

Therefore: switch from preempt_disable() to local_irq_save().
This prevents interrupts from interrupting the +=, and as a side effect
prevents preemption.

Link: https://lkml.kernel.org/r/20221216150441.200533-2-manfred@colorfullife.com
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: "Sun, Jiebin" <jiebin.sun@intel.com>
Cc: <1vier1@web.de>
Cc: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Manfred Spraul 2022-12-16 16:04:40 +01:00 committed by Andrew Morton
parent 805afd8300
commit 88ad32a799
1 changed files with 4 additions and 2 deletions
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6
include/linux/percpu_counter.h
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@ -152,9 +152,11 @@ __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch)
static inline void
percpu_counter_add(struct percpu_counter *fbc, s64 amount)
{
preempt_disable();
unsigned long flags;
local_irq_save(flags);
fbc->count += amount;
preempt_enable();
local_irq_restore(flags);
}
/* non-SMP percpu_counter_add_local is the same with percpu_counter_add */