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

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Message-ID: <170915761210.398.716787141204315247.tip-bot2@tip-bot2>
Date: Wed, 28 Feb 2024 22:00:12 -0000
From: "tip-bot2 for Shrikanth Hegde" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Shrikanth Hegde <sshegde@...ux.vnet.ibm.com>,
 Ingo Molnar <mingo@...nel.org>, Vincent Guittot <vincent.guittot@...aro.org>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/fair: Add READ_ONCE() and use existing helper
 function to access ->avg_irq

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@...ux.vnet.ibm.com>
AuthorDate:    Mon, 01 Jan 2024 21:16:24 +05:30
Committer:     Ingo Molnar <mingo@...nel.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@...ux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@...aro.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