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

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Date:	Wed, 17 Apr 2013 17:34:45 -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 03/26/13 10:35, Stephen Boyd wrote:
> On 03/21/13 10:49, Stephen Boyd wrote:
>> 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?
> Russell, should I put this into the patch tracker?

I'll throw this into the patch tracker tomorrow if nobody complains.

>>> 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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