Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751071AbaALQK6 (ORCPT ); Sun, 12 Jan 2014 11:10:58 -0500 Received: from mail-pa0-f51.google.com ([209.85.220.51]:61985 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750955AbaALQK4 (ORCPT ); Sun, 12 Jan 2014 11:10:56 -0500 From: Ming Lei To: Andrew Morton , linux-kernel@vger.kernel.org Cc: Paul Gortmaker , Shaohua Li , Jens Axboe , Fan Du , Ming Lei Subject: [PATCH] lib/percpu_counter.c: fix __percpu_counter_add Date: Mon, 13 Jan 2014 00:10:45 +0800 Message-Id: <1389543045-10563-1-git-send-email-tom.leiming@gmail.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andrew Morton __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 Cc: Shaohua Li Cc: Jens Axboe Cc: Fan Du Cc: Andrew Morton Signed-off-by: Ming Lei --- 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 majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/