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Date: Tue, 20 Feb 2024 20:20:02 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
 Masami Hiramatsu <mhiramat@kernel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@efficios.com>, Daniel Bristot de Oliveira
 <bristot@redhat.com>, Vincent Guittot <vincent.guittot@linaro.org>, Juri
 Lelli <juri.lelli@redhat.com>
Subject: [PATCH] sched/clock: Make local_clock() notrace
Message-ID: <20240220202002.38fec245@gandalf.local.home>
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From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The "perf" clock in /sys/kernel/tracing/trace_clock enables local_clock(),
where on machines that have CONFIG_HAVE_UNSTABLE_SCHED_CLOCK set is a
normal function. This function can be traced.

I found that enabling the "perf" clock on some debug configs and running
function tracer can live lock the machine. That is, it goes so slow that
nothing moves forward.

Cc: stable@vger.kernel.org
Fixes: fb7d4948c4da2 ("sched/clock: Provide local_clock_noinstr()")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 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 3c6193de9cde..af8b698dee8c 100644
--- a/kernel/sched/clock.c
+++ b/kernel/sched/clock.c
@@ -308,7 +308,7 @@ noinstr u64 local_clock_noinstr(void)
 	return clock;
 }
 
-u64 local_clock(void)
+notrace u64 local_clock(void)
 {
 	u64 now;
 	preempt_disable_notrace();
-- 
2.43.0