On Tue, 19 Apr 2016, Jiri Kosina wrote:
> From: Jiri Kosina <jkosina@xxxxxxx>
>
> bch_writeback_thread() is calling try_to_freeze(), but that's just an
> expensive no-op given the fact that the thread is not marked freezable.
>
> I/O helper kthreads, exactly such as the bcache writeback thread, actually
> shouldn't be freezable, because they are potentially necessary for
> finalizing the image write-out.
This is good timing, as Maciej Piechotka just reported a hang when
suspending his system.
What is the proper way to safely support suspend? Assuming the
try_to_freeze() calls are in the right place, should we simply
set_freezable() on these kthreads?
--
Eric Wheeler
>
> Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
> ---
> drivers/md/bcache/writeback.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
> index b9346cd..6012367 100644
> --- a/drivers/md/bcache/writeback.c
> +++ b/drivers/md/bcache/writeback.c
> @@ -12,7 +12,6 @@
> #include "writeback.h"
>
> #include <linux/delay.h>
> -#include <linux/freezer.h>
> #include <linux/kthread.h>
> #include <trace/events/bcache.h>
>
> @@ -228,7 +227,6 @@ static void read_dirty(struct cached_dev *dc)
> */
>
> while (!kthread_should_stop()) {
> - try_to_freeze();
>
> w = bch_keybuf_next(&dc->writeback_keys);
> if (!w)
> @@ -433,7 +431,6 @@ static int bch_writeback_thread(void *arg)
> if (kthread_should_stop())
> return 0;
>
> - try_to_freeze();
> schedule();
> continue;
> }
> --
> Jiri Kosina
> SUSE Labs
>
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