[PATCH] io-wq: set task TASK_INTERRUPTIBLE state before schedule_timeout

[PATCH] io-wq: set task TASK_INTERRUPTIBLE state before schedule_timeout

[qiang.zhang]

From: Zqiang <qiang.zhang@windriver.com>

In 'io_wqe_worker' thread, if the work which in 'wqe->work_list' be
finished, the 'wqe->work_list' is empty, and after that the
'__io_worker_idle' func return false, the task state is TASK_RUNNING,
need to be set TASK_INTERRUPTIBLE before call schedule_timeout func.

Signed-off-by: Zqiang <qiang.zhang@windriver.com>
---
 fs/io-wq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 02894df7656d..5f0626935b64 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -618,7 +618,7 @@ static int io_wqe_worker(void *data)
 		raw_spin_unlock_irq(&wqe->lock);
 		if (signal_pending(current))
 			flush_signals(current);
-		if (schedule_timeout(WORKER_IDLE_TIMEOUT))
+		if (schedule_timeout_interruptible(WORKER_IDLE_TIMEOUT))
 			continue;
 		/* timed out, exit unless we're the fixed worker */
 		if (test_bit(IO_WQ_BIT_EXIT, &wq->state) ||
-- 
2.17.1

[PATCH] io-wq: set task TASK_INTERRUPTIBLE state before schedule_timeout

[qiang.zhang]

From: Zqiang <qiang.zhang@windriver.com>

In 'io_wqe_worker' thread, if the work which in 'wqe->work_list' be
finished, the 'wqe->work_list' is empty, and after that the
'__io_worker_idle' func return false, the task state is TASK_RUNNING,
need to be set TASK_INTERRUPTIBLE before call schedule_timeout func.

Signed-off-by: Zqiang <qiang.zhang@windriver.com>
---
 fs/io-wq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 02894df7656d..5f0626935b64 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -618,7 +618,7 @@ static int io_wqe_worker(void *data)
 		raw_spin_unlock_irq(&wqe->lock);
 		if (signal_pending(current))
 			flush_signals(current);
-		if (schedule_timeout(WORKER_IDLE_TIMEOUT))
+		if (schedule_timeout_interruptible(WORKER_IDLE_TIMEOUT))
 			continue;
 		/* timed out, exit unless we're the fixed worker */
 		if (test_bit(IO_WQ_BIT_EXIT, &wq->state) ||
-- 
2.17.1

Re: [PATCH] io-wq: set task TASK_INTERRUPTIBLE state before schedule_timeout

[Jens Axboe]

On 10/26/20 9:09 PM, qiang.zhang@windriver.com wrote:
> From: Zqiang <qiang.zhang@windriver.com>
> 
> In 'io_wqe_worker' thread, if the work which in 'wqe->work_list' be
> finished, the 'wqe->work_list' is empty, and after that the
> '__io_worker_idle' func return false, the task state is TASK_RUNNING,
> need to be set TASK_INTERRUPTIBLE before call schedule_timeout func.

I don't think that's safe - what if someone added work right before you
call schedule_timeout_interruptible? Something ala:


io_wq_enqueue()
			set_current_state(TASK_INTERRUPTIBLE();
			schedule_timeout(WORKER_IDLE_TIMEOUT);

then we'll have work added and the task state set to running, but the
worker itself just sets us to non-running and will hence wait
WORKER_IDLE_TIMEOUT before the work is processed.

The current situation will do one extra loop for this case, as the
schedule_timeout() just ends up being a nop and we go around again
checking for work. Since we already unused the mm, the next iteration
will go to sleep properly unless new work came in.

-- 
Jens Axboe