Re: [PATCH 1/1] fs-writeback: Using spin_lock to check for work_list empty
From: Rajan Aggarwal <hidden>
Date: 2011-08-31 06:46:30
Also in:
linux-fsdevel
Hi Kamezawa, I noticed that you are responding to emails right now. Can you please review the patch below and tell me whether it is technically correct ? Or, can you please suggest a suitable change for solving this ? Thanks. Kautuk On Wed, Aug 31, 2011 at 10:41 AM, Rajan Aggarwal [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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