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From: <quanyang.wang@windriver.com>
To: <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Leo Yan <leo.yan@linaro.org>, Will Deacon <will@kernel.org>,
	<a.darwish@linutronix.de>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Paul Cercueil <paul@crapouillou.net>,
	Randy Dunlap <rdunlap@infradead.org>, <ben.dooks@codethink.co.uk>
Subject: [PATCH] time/sched_clock: mark sched_clock_read_begin as notrace
Date: Mon, 28 Sep 2020 18:49:52 +0800	[thread overview]
Message-ID: <20200928104952.26892-1-quanyang.wang@windriver.com> (raw)

From: Quanyang Wang <quanyang.wang@windriver.com>

Since sched_clock_read_begin is called by notrace function sched_clock,
it shouldn't be traceable either, or else __ftrace_graph_caller will
run into a dead loop on the path (arm for instance):

  ftrace_graph_caller
    prepare_ftrace_return
      function_graph_enter
        ftrace_push_return_trace
          trace_clock_local
            sched_clock
              sched_clock_read_begin

Fixes: 1b86abc1c645 ("sched_clock: Expose struct clock_read_data")
Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>
---
 kernel/time/sched_clock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
index 1c03eec6ca9b..58459e1359d7 100644
--- a/kernel/time/sched_clock.c
+++ b/kernel/time/sched_clock.c
@@ -68,7 +68,7 @@ static inline u64 notrace cyc_to_ns(u64 cyc, u32 mult, u32 shift)
 	return (cyc * mult) >> shift;
 }
 
-struct clock_read_data *sched_clock_read_begin(unsigned int *seq)
+notrace struct clock_read_data *sched_clock_read_begin(unsigned int *seq)
 {
 	*seq = raw_read_seqcount_latch(&cd.seq);
 	return cd.read_data + (*seq & 1);
-- 
2.17.1


             reply	other threads:[~2020-09-28 11:36 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-28 10:49 quanyang.wang [this message]
2020-09-28 10:58 ` [PATCH] time/sched_clock: mark sched_clock_read_begin as notrace Peter Zijlstra
2020-09-28 12:41   ` Quanyang Wang
2020-09-28 21:33   ` Steven Rostedt
2020-09-29  7:13     ` Peter Zijlstra
2020-09-29 14:43       ` Steven Rostedt

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