Because after kthread_create, the state of kthread is TASK_UNINTERRUPTIBLE. If we don't wake up dc->writeback_thread, the thread will be hung-task. For those reasons, we don't wake up writeback_thread: A:only create backed device B:create backed device and cache device, but don't write at once C:write without writeback poliy
So like the way of create gc_thread, after creating writeback_thread, i set the state is TASK_INTERRUPTIBLE. Signed-off-by: Jianpeng Ma <[email protected]> --- drivers/md/bcache/writeback.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c index 6c44fe0..7fbc22a 100644 --- a/drivers/md/bcache/writeback.c +++ b/drivers/md/bcache/writeback.c @@ -499,6 +499,8 @@ int bch_cached_dev_writeback_init(struct cached_dev *dc) if (IS_ERR(dc->writeback_thread)) return PTR_ERR(dc->writeback_thread); + set_task_state(dc->writeback_thread, TASK_INTERRUPTIBLE); + INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate); schedule_delayed_work(&dc->writeback_rate_update, dc->writeback_rate_update_seconds * HZ); -- 1.7.10.4
