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From: jszhang@marvell.com (Jisheng Zhang)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] clocksource/drivers/ti-32k: Prevent ftrace recursion
Date: Fri, 23 Sep 2016 10:04:31 +0800	[thread overview]
Message-ID: <20160923100431.6cf2c88f@xhacker> (raw)
In-Reply-To: <alpine.DEB.2.20.1609221555590.5599@nanos>

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

WARNING: multiple messages have this Message-ID (diff)
From: Jisheng Zhang <jszhang@marvell.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: <daniel.lezcano@linaro.org>, LKML <linux-kernel@vger.kernel.org>,
	LAK <linux-arm-kernel@lists.infradead.org>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH] clocksource/drivers/ti-32k: Prevent ftrace recursion
Date: Fri, 23 Sep 2016 10:04:31 +0800	[thread overview]
Message-ID: <20160923100431.6cf2c88f@xhacker> (raw)
In-Reply-To: <alpine.DEB.2.20.1609221555590.5599@nanos>

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

  parent reply	other threads:[~2016-09-23  2:04 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-22  7:56 [PATCH] clocksource/drivers/ti-32k: Prevent ftrace recursion Jisheng Zhang
2016-09-22  7:56 ` Jisheng Zhang
2016-09-22 13:58 ` Thomas Gleixner
2016-09-22 13:58   ` Thomas Gleixner
2016-09-22 14:29   ` Steven Rostedt
2016-09-22 14:29     ` Steven Rostedt
2016-09-23  2:04   ` Jisheng Zhang [this message]
2016-09-23  2:04     ` Jisheng Zhang
2016-09-23  2:45     ` Steven Rostedt
2016-09-23  2:45       ` Steven Rostedt
2016-09-23  2:48       ` Jisheng Zhang
2016-09-23  2:48         ` Jisheng Zhang
2016-09-22 14:54 ` [tip:timers/core] " tip-bot for Jisheng Zhang

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