From: Andrew Morton <[email protected]> __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.
The patch fixes problem that 'rmmod null_blk' hangs in blk_cleanup_queue() because of miscounting of request_queue->mq_usage_counter. Cc: Paul Gortmaker <[email protected]> Cc: Shaohua Li <[email protected]> Cc: Jens Axboe <[email protected]> Cc: Fan Du <[email protected]> Cc: Andrew Morton <[email protected]> Signed-off-by: Ming Lei <[email protected]> --- 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(). lib/percpu_counter.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c index 7473ee3..1da85bb 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); } preempt_enable(); } -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
