diff options
authorMing Lei <tom.leiming@gmail.com>2014-01-14 17:56:42 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-01-15 14:19:42 +0700
commit74e72f894d56eb9d2e1218530c658e7d297e002b (patch)
parent5a610fcc7390ee60308deaf09426ada87a1eeec2 (diff)
lib/percpu_counter.c: fix __percpu_counter_add()
__percpu_counter_add() may be called in softirq/hardirq handler (such as, blk_mq_queue_exit() is typically called in hardirq/softirq handler), so we need to call this_cpu_add()(irq safe helper) to update percpu counter, otherwise counts may be lost. This fixes the problem that 'rmmod null_blk' hangs in blk_cleanup_queue() because of miscounting of request_queue->mq_usage_counter. This patch is the v1 of previous one of "lib/percpu_counter.c: disable local irq when updating percpu couter", and takes Andrew's approach which may be more efficient for ARCHs(x86, s390) that have optimized this_cpu_add(). Signed-off-by: Ming Lei <tom.leiming@gmail.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Shaohua Li <shli@fusionio.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Fan Du <fan.du@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 2 insertions, 2 deletions
diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
index 7473ee3b4ee..1da85bb1bc0 100644
--- a/lib/percpu_counter.c
+++ b/lib/percpu_counter.c
@@ -82,10 +82,10 @@ void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch)
unsigned long flags;
raw_spin_lock_irqsave(&fbc->lock, flags);
fbc->count += count;
+ __this_cpu_sub(*fbc->counters, count);
raw_spin_unlock_irqrestore(&fbc->lock, flags);
- __this_cpu_write(*fbc->counters, 0);
} else {
- __this_cpu_write(*fbc->counters, count);
+ this_cpu_add(*fbc->counters, amount);