linux-kernel - Re: [PATCH] ARM: sched_clock: Add more notrace to prevent recursion

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Message-ID: <514B483F.7000304@codeaurora.org>
Date:	Thu, 21 Mar 2013 10:49:51 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Russell King <linux@....linux.org.uk>
CC:	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: sched_clock: Add more notrace to prevent recursion

On 03/14/13 17:08, Stephen Boyd wrote:
> cyc_to_sched_clock() is called by sched_clock() and cyc_to_ns()
> is called by cyc_to_sched_clock(). I suspect that some compilers
> inline both of these functions into sched_clock() and so we've
> been getting away without having a notrace marking. It seems that
> my compiler isn't inlining cyc_to_sched_clock() though, so I'm
> hitting a recursion bug when I enable the function graph tracer,
> causing my system to crash. Marking these functions notrace fixes
> it. Technically cyc_to_ns() doesn't need the notrace because it's
> already marked inline, but let's just add it so that if we ever
> remove inline from that function it doesn't blow up.

Anyone else seeing this problem?

>
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> ---
>  arch/arm/kernel/sched_clock.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/kernel/sched_clock.c b/arch/arm/kernel/sched_clock.c
> index bd6f56b..59d2adb 100644
> --- a/arch/arm/kernel/sched_clock.c
> +++ b/arch/arm/kernel/sched_clock.c
> @@ -45,12 +45,12 @@ static u32 notrace jiffy_sched_clock_read(void)
>  
>  static u32 __read_mostly (*read_sched_clock)(void) = jiffy_sched_clock_read;
>  
> -static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift)
> +static inline u64 notrace cyc_to_ns(u64 cyc, u32 mult, u32 shift)
>  {
>  	return (cyc * mult) >> shift;
>  }
>  
> -static unsigned long long cyc_to_sched_clock(u32 cyc, u32 mask)
> +static unsigned long long notrace cyc_to_sched_clock(u32 cyc, u32 mask)
>  {
>  	u64 epoch_ns;
>  	u32 epoch_cyc;

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