linux-kernel - [tip:perf/urgent] perf: Find_get_context: fix the per-cpu-counter check

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Message-ID: <tip-22a4ec729017ba613337a28f306f94ba5023fe2e@git.kernel.org>
Date:	Tue, 18 Jan 2011 19:06:59 GMT
From:	tip-bot for Oleg Nesterov <oleg@...hat.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, paulus@...ba.org, acme@...hat.com,
	hpa@...or.com, mingo@...hat.com, stern@...land.harvard.edu,
	a.p.zijlstra@...llo.nl, roland@...hat.com, fweisbec@...il.com,
	tglx@...utronix.de, oleg@...hat.com, mingo@...e.hu,
	prasad@...ux.vnet.ibm.com
Subject: [tip:perf/urgent] perf: Find_get_context: fix the per-cpu-counter check

Commit-ID:  22a4ec729017ba613337a28f306f94ba5023fe2e
Gitweb:     http://git.kernel.org/tip/22a4ec729017ba613337a28f306f94ba5023fe2e
Author:     Oleg Nesterov <oleg@...hat.com>
AuthorDate: Tue, 18 Jan 2011 17:10:08 +0100
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Tue, 18 Jan 2011 19:34:23 +0100

perf: Find_get_context: fix the per-cpu-counter check

If task == NULL, find_get_context() should always check that cpu
is correct.

Afaics, the bug was introduced by 38a81da2 "perf events: Clean
up pid passing", but even before that commit "&& cpu != -1" was
not exactly right, -ESRCH from find_task_by_vpid() is not
accurate.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Alan Stern <stern@...land.harvard.edu>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Prasad <prasad@...ux.vnet.ibm.com>
Cc: Roland McGrath <roland@...hat.com>
Cc: gregkh@...e.de
Cc: stable@...nel.org
LKML-Reference: <20110118161008.GB693@...hat.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/perf_event.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 76be4c7..a962b19 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2228,7 +2228,7 @@ find_get_context(struct pmu *pmu, struct task_struct *task, int cpu)
 	unsigned long flags;
 	int ctxn, err;
 
-	if (!task && cpu != -1) {
+	if (!task) {
 		/* Must be root to operate on a CPU event: */
 		if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
 			return ERR_PTR(-EACCES);
--
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