linux-kernel - Re: [PATCH 3.4 43/91] perf: Fix a race condition in perf_remove_from

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Message-ID: <20141201184324.GA5032@us.ibm.com>
Date:	Mon, 1 Dec 2014 10:43:24 -0800
From:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To:	lizf@...nel.org
Cc:	stable@...r.kernel.org, linux-kernel@...r.kernel.org,
	Cong Wang <cwang@...pensource.com>,
	Cong Wang <xiyou.wangcong@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>, Zefan Li <lizefan@...wei.com>
Subject: Re: [PATCH 3.4 43/91] perf: Fix a race condition in
 perf_remove_from_context()

lizf@...nel.org [lizf@...nel.org] wrote:
| From: Cong Wang <cwang@...pensource.com>
| 
| 3.4.105-rc1 review patch.  If anyone has any objections, please let me know.
| 
<snip>
| 
| diff --git a/kernel/events/core.c b/kernel/events/core.c
| index 685ce46..c958be1 100644
| --- a/kernel/events/core.c
| +++ b/kernel/events/core.c
| @@ -1702,6 +1702,16 @@ retry:
|  	 */
|  	if (ctx->is_active) {
|  		raw_spin_unlock_irq(&ctx->lock);
| +		/*
| +		 * Reload the task pointer, it might have been changed by
| +		 * a concurrent perf_event_context_sched_out().
| +		 */
| +		task = ctx->task;
| +		/*
| +		 * Reload the task pointer, it might have been changed by
| +		 * a concurrent perf_event_context_sched_out().
| +		 */
| +		task = ctx->task;

Something wrong in the way the patch was applied ?
The lines are identical...

The original commit, 3577af70, has the change applied in two
places: perf_event_disable() and perf_remove_from_context().

|  		goto retry;
|  	}
| 
| -- 
| 1.9.1
| 
| --
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