linux-kernel - [PATCH v4 1/2] sched/core: Remove ifdeffery for saved

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Message-ID: <20230908-avoid-spurious-freezer-wakeups-v4-1-6155aa3dafae@quicinc.com>
Date:   Fri, 8 Sep 2023 15:49:15 -0700
From:   Elliot Berman <quic_eberman@...cinc.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>
CC:     Thomas Gleixner <tglx@...utronix.de>, <kernel@...cinc.com>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-pm@...r.kernel.org>,
        Elliot Berman <quic_eberman@...cinc.com>
Subject: [PATCH v4 1/2] sched/core: Remove ifdeffery for saved_state

In preparation for freezer to also use saved_state, remove the
CONFIG_PREEMPT_RT compilation guard around saved_state.

On the arm64 platform I tested which did not have CONFIG_PREEMPT_RT,
there was no statistically significant deviation by applying this patch.

Test methodology:

perf bench sched message -g 40 -l 40

Signed-off-by: Elliot Berman <quic_eberman@...cinc.com>
---
 include/linux/sched.h |  2 --
 kernel/sched/core.c   | 17 +++--------------
 2 files changed, 3 insertions(+), 16 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 609bde814cb0..14194a62294f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -745,10 +745,8 @@ struct task_struct {
 #endif
 	unsigned int			__state;
 
-#ifdef CONFIG_PREEMPT_RT
 	/* saved state for "spinlock sleepers" */
 	unsigned int			saved_state;
-#endif
 
 	/*
 	 * This begins the randomizable portion of task_struct. Only
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c52c2eba7c73..58921ab7442b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2219,31 +2219,21 @@ int __task_state_match(struct task_struct *p, unsigned int state)
 	if (READ_ONCE(p->__state) & state)
 		return 1;
 
-#ifdef CONFIG_PREEMPT_RT
 	if (READ_ONCE(p->saved_state) & state)
 		return -1;
-#endif
+
 	return 0;
 }
 
 static __always_inline
 int task_state_match(struct task_struct *p, unsigned int state)
 {
-#ifdef CONFIG_PREEMPT_RT
-	int match;
-
 	/*
 	 * Serialize against current_save_and_set_rtlock_wait_state() and
 	 * current_restore_rtlock_saved_state().
 	 */
-	raw_spin_lock_irq(&p->pi_lock);
-	match = __task_state_match(p, state);
-	raw_spin_unlock_irq(&p->pi_lock);
-
-	return match;
-#else
+	guard(raw_spinlock_irq)(&p->pi_lock);
 	return __task_state_match(p, state);
-#endif
 }
 
 /*
@@ -4053,7 +4043,6 @@ bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success)
 
 	*success = !!(match = __task_state_match(p, state));
 
-#ifdef CONFIG_PREEMPT_RT
 	/*
 	 * Saved state preserves the task state across blocking on
 	 * an RT lock.  If the state matches, set p::saved_state to
@@ -4069,7 +4058,7 @@ bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success)
 	 */
 	if (match < 0)
 		p->saved_state = TASK_RUNNING;
-#endif
+
 	return match > 0;
 }
 

-- 
2.41.0