linux-kernel - [PATCH RFC] preempt: Put preempt_enable() within an instrumentation*() section.

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Date:   Thu, 9 Mar 2023 08:27:24 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Mel Gorman <mgorman@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Valentin Schneider <vschneid@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH RFC] preempt: Put preempt_enable() within an
 instrumentation*() section.

Callers of preempt_enable() can be within an noinstr section leading to:
| vmlinux.o: warning: objtool: native_sched_clock+0x97: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section
| vmlinux.o: warning: objtool: kvm_clock_read+0x22: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section
| vmlinux.o: warning: objtool: local_clock+0xb4: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section
| vmlinux.o: warning: objtool: enter_from_user_mode+0xea: call to preempt_schedule_thunk() leaves .noinstr.text section
| vmlinux.o: warning: objtool: syscall_enter_from_user_mode+0x140: call to preempt_schedule_thunk() leaves .noinstr.text section
| vmlinux.o: warning: objtool: syscall_enter_from_user_mode_prepare+0xf2: call to preempt_schedule_thunk() leaves .noinstr.text section
| vmlinux.o: warning: objtool: irqentry_enter_from_user_mode+0xea: call to preempt_schedule_thunk() leaves .noinstr.text section

This only happens on CONFIG_PREEMPT+ due to the conditional call into the scheduler.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 include/linux/preempt.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 12f59cdaaedda..05338f00a5907 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -238,15 +238,21 @@ do { \
 #define preempt_enable() \
 do { \
 	barrier(); \
-	if (unlikely(preempt_count_dec_and_test())) \
+	if (unlikely(preempt_count_dec_and_test())) { \
+		instrumentation_begin(); \
 		__preempt_schedule(); \
+		instrumentation_end(); \
+	} \
 } while (0)
 
 #define preempt_enable_notrace() \
 do { \
 	barrier(); \
-	if (unlikely(__preempt_count_dec_and_test())) \
+	if (unlikely(__preempt_count_dec_and_test())) { \
+		instrumentation_begin(); \
 		__preempt_schedule_notrace(); \
+		instrumentation_end(); \
+	} \
 } while (0)
 
 #define preempt_check_resched() \
-- 
2.39.2