Re: [PATCH] clocksource/drivers/ti-32k: Prevent ftrace recursion

From	Jisheng Zhang <jszhang@marvell.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] clocksource/drivers/ti-32k: Prevent ftrace recursion
Date	2016-09-23 04:10 +0200
Message-ID	<sko65-5Wq-3@gated-at.bofh.it> (permalink)
References	<sk7eV-3OW-15@gated-at.bofh.it> <skcRk-7nx-15@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hi Thomas,

On Thu, 22 Sep 2016 15:58:03 +0200 Thomas Gleixner wrote:

> On Thu, 22 Sep 2016, Jisheng Zhang wrote:
> 
> > Currently ti-32k can be used as a scheduler clock. We properly marked
> > omap_32k_read_sched_clock() as notrace but we then call another
> > function ti_32k_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.  
> 
> Kernel crash? Doesn't ftrace core prevent recursion?

a recent similar issue:

http://www.spinics.net/lists/arm-kernel/msg533480.html

Thanks,
Jisheng

Thread

[PATCH] clocksource/drivers/ti-32k: Prevent ftrace recursion Jisheng Zhang <jszhang@marvell.com> - 2016-09-22 10:10 +0200
  Re: [PATCH] clocksource/drivers/ti-32k: Prevent ftrace recursion Thomas Gleixner <tglx@linutronix.de> - 2016-09-22 16:10 +0200
    Re: [PATCH] clocksource/drivers/ti-32k: Prevent ftrace recursion Steven Rostedt <rostedt@goodmis.org> - 2016-09-22 16:30 +0200
    Re: [PATCH] clocksource/drivers/ti-32k: Prevent ftrace recursion Jisheng Zhang <jszhang@marvell.com> - 2016-09-23 04:10 +0200
      Re: [PATCH] clocksource/drivers/ti-32k: Prevent ftrace recursion Steven Rostedt <rostedt@goodmis.org> - 2016-09-23 04:50 +0200
        Re: [PATCH] clocksource/drivers/ti-32k: Prevent ftrace recursion Jisheng Zhang <jszhang@marvell.com> - 2016-09-23 05:00 +0200
  [tip:timers/core] clocksource/drivers/ti-32k: Prevent ftrace  recursion tip-bot for Jisheng Zhang <tipbot@zytor.com> - 2016-09-22 17:00 +0200

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