linux-kernel - [PATCH 2/8] clocksource/drivers/pistachio: Prevent ftrace recursion

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Date:	Wed, 28 Oct 2015 14:11:27 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	tglx@...utronix.de
Cc:	Jisheng Zhang <jszhang@...vell.com>,
	linux-kernel@...r.kernel.org (open list:CLOCKSOURCE, CLOC...)
Subject: [PATCH 2/8] clocksource/drivers/pistachio: Prevent ftrace recursion

From: Jisheng Zhang <jszhang@...vell.com>

Currently pistachio can be used as a scheduler clock. We properly marked
pistachio_read_sched_clock() as notrace but we then call another function
pistachio_clocksource_read_cycles() that _wasn't_ notrace.

Having a traceable function in the sched_clock() path leads to a recursion
within ftrace and a kernel crash.

Fix this by adding notrace attribute to the pistachio_clocksource_read_cycles()
function.

Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
---
 drivers/clocksource/time-pistachio.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/time-pistachio.c b/drivers/clocksource/time-pistachio.c
index 18d4266..bba6799 100644
--- a/drivers/clocksource/time-pistachio.c
+++ b/drivers/clocksource/time-pistachio.c
@@ -67,7 +67,8 @@ static inline void gpt_writel(void __iomem *base, u32 value, u32 offset,
 	writel(value, base + 0x20 * gpt_id + offset);
 }
 
-static cycle_t pistachio_clocksource_read_cycles(struct clocksource *cs)
+static cycle_t notrace
+pistachio_clocksource_read_cycles(struct clocksource *cs)
 {
 	struct pistachio_clocksource *pcs = to_pistachio_clocksource(cs);
 	u32 counter, overflw;
-- 
1.9.1

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