sched: use existing helper function for accessing avg_rt, avg_dl and avg_irq

[PATCH v2 2/2] sched: add READ_ONCE and use existing helper function to access ->avg_irq

Posted by Shrikanth Hegde 1 year, 12 months ago

Use existing helper function cpu_util_irq instead of referencing it
directly.

It was noted that avg_irq could be updated by different CPU than the one
which is trying to access it. avg_irq is updated with WRITE_ONCE. Use
READ_ONCE to access it in order to avoid any compiler optimizations.

Signed-off-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com>
---
 kernel/sched/fair.c  | 4 +---
 kernel/sched/sched.h | 2 +-
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1aeca3f943a8..02631060ca7e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9221,10 +9221,8 @@ static inline bool others_have_blocked(struct rq *rq)
 	if (thermal_load_avg(rq))
 		return true;

-#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
-	if (READ_ONCE(rq->avg_irq.util_avg))
+	if (cpu_util_irq(rq))
 		return true;
-#endif

 	return false;
 }
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e58a54bda77d..edc20c5cc7ce 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3125,7 +3125,7 @@ static inline bool uclamp_rq_is_idle(struct rq *rq)
 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
 static inline unsigned long cpu_util_irq(struct rq *rq)
 {
-	return rq->avg_irq.util_avg;
+	return READ_ONCE(rq->avg_irq.util_avg);
 }

 static inline
--
2.39.3

Re: [PATCH v2 2/2] sched: add READ_ONCE and use existing helper function to access ->avg_irq

Posted by Vincent Guittot 1 year, 11 months ago

On Mon, 1 Jan 2024 at 16:47, Shrikanth Hegde <sshegde@linux.vnet.ibm.com> wrote:
>
> Use existing helper function cpu_util_irq instead of referencing it
> directly.
>
> It was noted that avg_irq could be updated by different CPU than the one
> which is trying to access it. avg_irq is updated with WRITE_ONCE. Use
> READ_ONCE to access it in order to avoid any compiler optimizations.
>
> Signed-off-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com>

Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>

> ---
>  kernel/sched/fair.c  | 4 +---
>  kernel/sched/sched.h | 2 +-
>  2 files changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 1aeca3f943a8..02631060ca7e 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -9221,10 +9221,8 @@ static inline bool others_have_blocked(struct rq *rq)
>         if (thermal_load_avg(rq))
>                 return true;
>
> -#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
> -       if (READ_ONCE(rq->avg_irq.util_avg))
> +       if (cpu_util_irq(rq))
>                 return true;
> -#endif
>
>         return false;
>  }
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index e58a54bda77d..edc20c5cc7ce 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -3125,7 +3125,7 @@ static inline bool uclamp_rq_is_idle(struct rq *rq)
>  #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
>  static inline unsigned long cpu_util_irq(struct rq *rq)
>  {
> -       return rq->avg_irq.util_avg;
> +       return READ_ONCE(rq->avg_irq.util_avg);
>  }
>
>  static inline
> --
> 2.39.3
>

[tip: sched/core] sched/fair: Add READ_ONCE() and use existing helper function to access ->avg_irq

Posted by tip-bot2 for Shrikanth Hegde 1 year, 10 months ago

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

Commit-ID:     a6965b31888501f889261a6783f0de6afff84f8d
Gitweb:        https://git.kernel.org/tip/a6965b31888501f889261a6783f0de6afff84f8d
Author:        Shrikanth Hegde <sshegde@linux.vnet.ibm.com>
AuthorDate:    Mon, 01 Jan 2024 21:16:24 +05:30
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 28 Feb 2024 15:11:15 +01:00

sched/fair: Add READ_ONCE() and use existing helper function to access ->avg_irq

Use existing helper function cpu_util_irq() instead of open-coding
access to ->avg_irq.

During review it was noted that ->avg_irq could be updated by a
different CPU than the one which is trying to access it.

->avg_irq is updated with WRITE_ONCE(), use READ_ONCE to access it
in order to avoid any compiler optimizations.

Signed-off-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20240101154624.100981-3-sshegde@linux.vnet.ibm.com
---
 kernel/sched/fair.c  | 4 +---
 kernel/sched/sched.h | 2 +-
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 127e727..ba36339 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9246,10 +9246,8 @@ static inline bool others_have_blocked(struct rq *rq)
 	if (thermal_load_avg(rq))
 		return true;
 
-#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
-	if (READ_ONCE(rq->avg_irq.util_avg))
+	if (cpu_util_irq(rq))
 		return true;
-#endif
 
 	return false;
 }
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 001fe04..d224267 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3136,7 +3136,7 @@ static inline bool uclamp_rq_is_idle(struct rq *rq)
 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
 static inline unsigned long cpu_util_irq(struct rq *rq)
 {
-	return rq->avg_irq.util_avg;
+	return READ_ONCE(rq->avg_irq.util_avg);
 }
 
 static inline