linux-kernel - [PATCH] clocksource/arm_arch_timer: Don't trace count reader functions

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Message-Id: <1558689025-50679-1-git-send-email-julien.thierry@arm.com>
Date:   Fri, 24 May 2019 10:10:25 +0100
From:   Julien Thierry <julien.thierry@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org,
        Julien Thierry <julien.thierry@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Mark Rutland <mark.rutland@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH] clocksource/arm_arch_timer: Don't trace count reader functions

With v5.2-rc1, The ftrace functions_graph tracer locks up whenever it is
enabled on arm64.

Since commit 0ea415390cd3 ("clocksource/arm_arch_timer: Use
arch_timer_read_counter to access stable counters") a function pointer
is consistently used to read the counter instead of potentially
referencing an inlinable function.

The graph tacers relies on accessing the timer counters to compute the
time spent in functions which causes the lockup when attempting to trace
these code paths.

Annontate the arm arch timer counter accessors as notrace.

Fixes: 0ea415390cd3 ("clocksource/arm_arch_timer: Use
       arch_timer_read_counter to access stable counters")
Signed-off-by: Julien Thierry <julien.thierry@....com>
Cc: Marc Zyngier <marc.zyngier@....com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Steven Rostedt <rostedt@...dmis.org>
---
 drivers/clocksource/arm_arch_timer.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index b2a951a..5c69c9a 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -149,22 +149,22 @@ u32 arch_timer_reg_read(int access, enum arch_timer_reg reg,
 	return val;
 }
 
-static u64 arch_counter_get_cntpct_stable(void)
+static notrace u64 arch_counter_get_cntpct_stable(void)
 {
 	return __arch_counter_get_cntpct_stable();
 }
 
-static u64 arch_counter_get_cntpct(void)
+static notrace u64 arch_counter_get_cntpct(void)
 {
 	return __arch_counter_get_cntpct();
 }
 
-static u64 arch_counter_get_cntvct_stable(void)
+static notrace u64 arch_counter_get_cntvct_stable(void)
 {
 	return __arch_counter_get_cntvct_stable();
 }
 
-static u64 arch_counter_get_cntvct(void)
+static notrace u64 arch_counter_get_cntvct(void)
 {
 	return __arch_counter_get_cntvct();
 }
-- 
1.9.1