From 5a042aa4b8e994a15d2c2ee750219971f0ab3905 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Fri, 2 Sep 2011 17:04:09 -0600 Subject: mm: Cleanup clearing of BDI_pending bit in bdi_forker_thread() bdi_forker_thread() clears BDI_pending bit at the end of the main loop. However clearing of this bit must not be done in some cases which is handled by calling 'continue' from switch statement. That's kind of unusual construct and without a good reason so change the function into more intuitive code flow. CC: Wu Fengguang CC: Andrew Morton Signed-off-by: Jan Kara Signed-off-by: Jens Axboe --- mm/backing-dev.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) (limited to 'mm') diff --git a/mm/backing-dev.c b/mm/backing-dev.c index d6edf8d14f9c..94a047bb6c39 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -359,6 +359,17 @@ static unsigned long bdi_longest_inactive(void) return max(5UL * 60 * HZ, interval); } +/* + * Clear pending bit and wakeup anybody waiting for flusher thread creation or + * shutdown + */ +static void bdi_clear_pending(struct backing_dev_info *bdi) +{ + clear_bit(BDI_pending, &bdi->state); + smp_mb__after_clear_bit(); + wake_up_bit(&bdi->state, BDI_pending); +} + static int bdi_forker_thread(void *ptr) { struct bdi_writeback *me = ptr; @@ -469,11 +480,13 @@ static int bdi_forker_thread(void *ptr) spin_unlock_bh(&bdi->wb_lock); wake_up_process(task); } + bdi_clear_pending(bdi); break; case KILL_THREAD: __set_current_state(TASK_RUNNING); kthread_stop(task); + bdi_clear_pending(bdi); break; case NO_ACTION: @@ -489,16 +502,8 @@ static int bdi_forker_thread(void *ptr) else schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10)); try_to_freeze(); - /* Back to the main loop */ - continue; + break; } - - /* - * Clear pending bit and wakeup anybody waiting to tear us down. - */ - clear_bit(BDI_pending, &bdi->state); - smp_mb__after_clear_bit(); - wake_up_bit(&bdi->state, BDI_pending); } return 0; -- cgit v1.2.3-59-g8ed1b From 09f40f98bfa2ac22a332a713629a2f8f92896834 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Fri, 2 Sep 2011 17:04:10 -0600 Subject: mm: Add comment explaining task state setting in bdi_forker_thread() CC: Wu Fengguang CC: Andrew Morton Signed-off-by: Jan Kara Signed-off-by: Jens Axboe --- mm/backing-dev.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'mm') diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 94a047bb6c39..a87da524a4a0 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -401,6 +401,13 @@ static int bdi_forker_thread(void *ptr) } spin_lock_bh(&bdi_lock); + /* + * In the following loop we are going to check whether we have + * some work to do without any synchronization with tasks + * waking us up to do work for them. So we have to set task + * state already here so that we don't miss wakeups coming + * after we verify some condition. + */ set_current_state(TASK_INTERRUPTIBLE); list_for_each_entry(bdi, &bdi_list, bdi_list) { -- cgit v1.2.3-59-g8ed1b