linux-kernel - [RFC PATCH v3 08/15] sched/clock, x86: Make __sched_clock

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Message-ID: <20241119153502.41361-9-vschneid@redhat.com>
Date: Tue, 19 Nov 2024 16:34:55 +0100
From: Valentin Schneider <vschneid@...hat.com>
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Subject: [RFC PATCH v3 08/15] sched/clock, x86: Make __sched_clock_stable forceful

Later commits will cause objtool to warn about non __ro_after_init static
keys being used in .noinstr sections in order to safely defer instruction
patching IPIs targeted at NOHZ_FULL CPUs.

__sched_clock_stable is used in .noinstr code, and can be modified at
runtime (e.g. KVM module loading). Suppressing the text_poke_sync() IPI has
little benefits for this key, as NOHZ_FULL is incompatible with an unstable
TSC anyway.

Mark it as forceful to let the kernel know to always send the
text_poke_sync() IPI for it, and to let objtool know not to warn about it.

Signed-off-by: Valentin Schneider <vschneid@...hat.com>
---
 kernel/sched/clock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c
index 200e5568b9894..dc94b3717f5ce 100644
--- a/kernel/sched/clock.c
+++ b/kernel/sched/clock.c
@@ -76,7 +76,7 @@ static DEFINE_STATIC_KEY_FALSE_RO(sched_clock_running);
  * Similarly we start with __sched_clock_stable_early, thereby assuming we
  * will become stable, such that there's only a single 1 -> 0 transition.
  */
-static DEFINE_STATIC_KEY_FALSE(__sched_clock_stable);
+static DEFINE_STATIC_KEY_FALSE_FORCE(__sched_clock_stable);
 static int __sched_clock_stable_early = 1;
 
 /*
-- 
2.43.0