Messages in this thread Patch in this message | | | From | Manfred Spraul <> | Subject | [PATCH 2/3] include/linux/percpu_counter.h: Race in uniprocessor percpu_counter_add() | Date | Fri, 16 Dec 2022 16:04:40 +0100 |
| |
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.
Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Cc: "Sun, Jiebin" <jiebin.sun@intel.com> --- include/linux/percpu_counter.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h index a3aae8d57a42..521a733e21a9 100644 --- a/include/linux/percpu_counter.h +++ b/include/linux/percpu_counter.h @@ -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 */ -- 2.38.1
| |