linux-kernel - Re: [PATCH v2] oprofile: Fix the hang while offline the cpu

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Message-ID: <20101028001257.GZ5969@erda.amd.com>
Date:	Thu, 28 Oct 2010 02:12:57 +0200
From:	Robert Richter <robert.richter@....com>
To:	Santosh Shilimkar <santosh.shilimkar@...com>
CC:	"oprofile-list@...ts.sf.net" <oprofile-list@...ts.sf.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	sricharan <r.sricharan@...com>
Subject: Re: [PATCH v2] oprofile: Fix the hang while offline the cpu

On 27.10.10 11:17:15, Santosh Shilimkar wrote:
> The kernel build with CONFIG_OPROFILE and CPU_HOTPLUG enabled.
> The oprofile is initialised using system timer in absence of hardware
> counters supports. Oprofile isn't started from userland.
> 
> In this setup while doing a CPU offline the kernel hangs in infinite
> for loop inside lock_hrtimer_base() function
> 
> This happens because as part of oprofile_cpu_notify(, it tries to
> stop an hrtimer which was never started. These per-cpu hrtimers
> are started when the oprfile is started.
> 	echo 1	> /dev/oprofile/enable
> 
> This problem also existwhen the cpu is booted with maxcpus parameter
> set. When bringing the remaining cpus online the timers are started
> even if oprofile is not yet enabled.
> 
> This patch fix this issue by adding a state variable so that
> these hrtimer start/stop is only attempted when oprofile is
> started
> 
> Reported-by: Jan Sebastien <s-jan@...com>
> Signed-off-by: sricharan <r.sricharan@...com>
> Tested-by: sricharan <r.sricharan@...com>
> Cc: Robert Richter <robert.richter@....com>
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...com>
> ---
> V2: Updated patch with comments from Robert Richter
>  drivers/oprofile/timer_int.c |   13 +++++++++++++
>  1 files changed, 13 insertions(+), 0 deletions(-)

Applied to oprofile/urgent, thanks Santosh.

-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center

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