On Tue, Nov 22 2016, Shaohua Li wrote:
> There is mechanism to suspend a kernel thread. Use it instead of playing
> create/destroy game.
Good idea!
>
> Signed-off-by: Shaohua Li <shli@xxxxxx>
> ---
> drivers/md/md.c | 4 +++-
> drivers/md/raid5-cache.c | 18 +++++-------------
> 2 files changed, 8 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index d3cef77..f548469 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -7136,10 +7136,12 @@ static int md_thread(void *arg)
> wait_event_interruptible_timeout
> (thread->wqueue,
> test_bit(THREAD_WAKEUP, &thread->flags)
> - || kthread_should_stop(),
> + || kthread_should_stop() || kthread_should_park(),
> thread->timeout);
>
> clear_bit(THREAD_WAKEUP, &thread->flags);
> + if (kthread_should_park())
> + kthread_parkme();
> if (!kthread_should_stop())
> thread->run(thread);
> }
> diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
> index 8cb79fc..5f817bd 100644
> --- a/drivers/md/raid5-cache.c
> +++ b/drivers/md/raid5-cache.c
> @@ -19,6 +19,7 @@
> #include <linux/raid/md_p.h>
> #include <linux/crc32c.h>
> #include <linux/random.h>
> +#include <linux/kthread.h>
> #include "md.h"
> #include "raid5.h"
> #include "bitmap.h"
> @@ -1437,23 +1438,14 @@ void r5l_quiesce(struct r5l_log *log, int state)
> struct mddev *mddev;
> if (!log || state == 2)
> return;
> - if (state == 0) {
> - /*
> - * This is a special case for hotadd. In suspend, the array has
> - * no journal. In resume, journal is initialized as well as the
> - * reclaim thread.
> - */
> - if (log->reclaim_thread)
> - return;
> - log->reclaim_thread = md_register_thread(r5l_reclaim_thread,
> - log->rdev->mddev, "reclaim");
> - log->reclaim_thread->timeout = R5C_RECLAIM_WAKEUP_INTERVAL;
> - } else if (state == 1) {
> + if (state == 0)
> + kthread_unpark(log->reclaim_thread->tsk);
The old code tested for log->reclaim_thread being NULL. This new
version will just crash.
> + else if (state == 1) {
> /* make sure r5l_write_super_and_discard_space exits */
> mddev = log->rdev->mddev;
> wake_up(&mddev->sb_wait);
> + kthread_park(log->reclaim_thread->tsk);
r5l_do_reclaim has a wait loop internally. I think you need that to
abort when kthread_should_park(), else this will block indefinitely.
Thanks,
NeilBrown
> r5l_wake_reclaim(log, MaxSector);
> - md_unregister_thread(&log->reclaim_thread);
> r5l_do_reclaim(log);
> }
> }
> --
> 2.9.3
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