From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rajan Aggarwal Subject: [PATCH 1/1] fs-writeback: Using spin_lock to check for work_list empty Date: Wed, 31 Aug 2011 10:41:49 +0530 Message-ID: <1314767509-17862-1-git-send-email-rajan.aggarwal85@gmail.com> Cc: linux-kernel@vger.kernel.org, Rajan Aggarwal To: linux-fsdevel@vger.kernel.org Return-path: Received: from mail-yi0-f46.google.com ([209.85.218.46]:43032 "EHLO mail-yi0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752950Ab1HaFMI (ORCPT ); Wed, 31 Aug 2011 01:12:08 -0400 Sender: linux-fsdevel-owner@vger.kernel.org List-ID: The bdi_writeback_thread function does not use spin_lock to see if the work_list is empty. If the list is not empty, and if an interrupt happens before we set the current->state to TASK_RUNNING then we could be stuck in a schedule() due to kernel preemption. This patch acquires and releases the wb_lock to avoid this scenario. Signed-off-by: Rajan Aggarwal --- fs/fs-writeback.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 04cf3b9..e333898 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -936,11 +936,14 @@ int bdi_writeback_thread(void *data) if (pages_written) wb->last_active = jiffies; + spin_lock_bh(&bdi->wb_lock); set_current_state(TASK_INTERRUPTIBLE); if (!list_empty(&bdi->work_list) || kthread_should_stop()) { __set_current_state(TASK_RUNNING); + spin_unlock_bh(&bdi->wb_lock); continue; } + spin_unlock_bh(&bdi->wb_lock); if (wb_has_dirty_io(wb) && dirty_writeback_interval) schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10)); -- 1.7.4.1