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SubjectRe: [PATCH 1/3] sched/wait: use freezable_schedule when possible
On Fri, Feb 01, 2019 at 06:38:05AM +0100, Hugo Lefeuvre wrote:
> Replace schedule(); try_to_freeze() by freezable_schedule().
>
> Tasks calling freezable_schedule() set the PF_FREEZER_SKIP flag
> before calling schedule(). Unlike tasks calling schedule();
> try_to_freeze() tasks calling freezable_schedule() are not awaken by
> try_to_freeze_tasks(). Instead they call try_to_freeze() when they
> wake up if the freeze is still underway.
>
> It is not a problem since sleeping tasks can't do anything which isn't
> allowed for a frozen task while sleeping.
>
> The result is a potential performance gain during freeze, since less
> tasks have to be awaken.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>

thanks,

- Joel

>
> Signed-off-by: Hugo Lefeuvre <hle@owl.eu.com>
> ---
> include/linux/wait.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/wait.h b/include/linux/wait.h
> index ed7c122cb31f..5f3efabc36f4 100644
> --- a/include/linux/wait.h
> +++ b/include/linux/wait.h
> @@ -308,7 +308,7 @@ do { \
>
> #define __wait_event_freezable(wq_head, condition) \
> ___wait_event(wq_head, condition, TASK_INTERRUPTIBLE, 0, 0, \
> - schedule(); try_to_freeze())
> + freezable_schedule())
>
> /**
> * wait_event_freezable - sleep (or freeze) until a condition gets true
> @@ -367,7 +367,7 @@ do { \
> #define __wait_event_freezable_timeout(wq_head, condition, timeout) \
> ___wait_event(wq_head, ___wait_cond_timeout(condition), \
> TASK_INTERRUPTIBLE, 0, timeout, \
> - __ret = schedule_timeout(__ret); try_to_freeze())
> + __ret = freezable_schedule_timeout(__ret))
>
> /*
> * like wait_event_timeout() -- except it uses TASK_INTERRUPTIBLE to avoid
> @@ -588,7 +588,7 @@ do { \
>
> #define __wait_event_freezable_exclusive(wq, condition) \
> ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 1, 0, \
> - schedule(); try_to_freeze())
> + freezable_schedule())
>
> #define wait_event_freezable_exclusive(wq, condition) \
> ({ \
> --
> 2.20.1

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