[PATCH] sched/core: Use do-while instead of for loop in set_nr_if_polling

[PATCH] sched/core: Use do-while instead of for loop in set_nr_if_polling

[Uros Bizjak]

Use equivalent do-while loop instead of infinite for loop.

There are no asm code changes.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
---
 kernel/sched/core.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index af017e038b48..349c018eaf09 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -899,14 +899,13 @@ static bool set_nr_if_polling(struct task_struct *p)
 	struct thread_info *ti = task_thread_info(p);
 	typeof(ti->flags) val = READ_ONCE(ti->flags);
 
-	for (;;) {
+	do {
 		if (!(val & _TIF_POLLING_NRFLAG))
 			return false;
 		if (val & _TIF_NEED_RESCHED)
 			return true;
-		if (try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED))
-			break;
-	}
+	} while (!try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED));
+
 	return true;
 }
 
-- 
2.39.2

Re: [PATCH] sched/core: Use do-while instead of for loop in set_nr_if_polling

[Uros Bizjak]

I would like to ping for the patch below. The patch normalizes
try_cmpxchg loop to a more readable "while" instead of "for (;;)"
loop, otherwise it is a nop.

https://lore.kernel.org/lkml/20230228161426.4508-1-ubizjak@gmail.com/

Uros.



On Tue, Feb 28, 2023 at 5:14 PM Uros Bizjak <ubizjak@gmail.com> wrote:
>
> Use equivalent do-while loop instead of infinite for loop.
>
> There are no asm code changes.
>
> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Vincent Guittot <vincent.guittot@linaro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ben Segall <bsegall@google.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
> Cc: Christian Brauner <brauner@kernel.org>
> ---
>  kernel/sched/core.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index af017e038b48..349c018eaf09 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -899,14 +899,13 @@ static bool set_nr_if_polling(struct task_struct *p)
>         struct thread_info *ti = task_thread_info(p);
>         typeof(ti->flags) val = READ_ONCE(ti->flags);
>
> -       for (;;) {
> +       do {
>                 if (!(val & _TIF_POLLING_NRFLAG))
>                         return false;
>                 if (val & _TIF_NEED_RESCHED)
>                         return true;
> -               if (try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED))
> -                       break;
> -       }
> +       } while (!try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED));
> +
>         return true;
>  }
>
> --
> 2.39.2
>

[tip: sched/core] sched/core: Use do-while instead of for loop in set_nr_if_polling()

[tip-bot2 for Uros Bizjak]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     4ff34ad3d39377d9f6953f3606ccf611ce636767
Gitweb:        https://git.kernel.org/tip/4ff34ad3d39377d9f6953f3606ccf611ce636767
Author:        Uros Bizjak <ubizjak@gmail.com>
AuthorDate:    Tue, 28 Feb 2023 17:14:26 +01:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Fri, 15 Sep 2023 17:18:02 +02:00

sched/core: Use do-while instead of for loop in set_nr_if_polling()

Use equivalent do-while loop instead of infinite for loop.

There are no asm code changes.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230228161426.4508-1-ubizjak@gmail.com
---
 kernel/sched/core.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 76662d8..f39482d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -919,14 +919,13 @@ static bool set_nr_if_polling(struct task_struct *p)
 	struct thread_info *ti = task_thread_info(p);
 	typeof(ti->flags) val = READ_ONCE(ti->flags);
 
-	for (;;) {
+	do {
 		if (!(val & _TIF_POLLING_NRFLAG))
 			return false;
 		if (val & _TIF_NEED_RESCHED)
 			return true;
-		if (try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED))
-			break;
-	}
+	} while (!try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED));
+
 	return true;
 }