linux-kernel - [tip:perf/urgent] perf sched latency: Fix thread pid reuse issue

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Message-ID: <tip-o4doazhhv0zax5zshkg8hnys@git.kernel.org>
Date:	Sat, 7 Nov 2015 23:31:22 -0800
From:	tip-bot for Jiri Olsa <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com,
	a.p.zijlstra@...llo.nl, acme@...hat.com, moagrawa@...hat.com,
	namhyung@...nel.org, mingo@...nel.org, jolsa@...nel.org,
	dsahern@...il.com, tglx@...utronix.de
Subject: [tip:perf/urgent] perf sched latency: Fix thread pid reuse issue

Commit-ID:  0014de172d228e450377d1fd079d94e67128d27f
Gitweb:     http://git.kernel.org/tip/0014de172d228e450377d1fd079d94e67128d27f
Author:     Jiri Olsa <jolsa@...nel.org>
AuthorDate: Mon, 2 Nov 2015 12:10:25 +0100
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Thu, 5 Nov 2015 12:51:00 -0300

perf sched latency: Fix thread pid reuse issue

The latency subcommand holds a tree of working atoms sorted by thread's
pid/tid. If there's new thread with same pid and tid, the old working atom is
found and assert bug condition is hit in search function:

  thread_atoms_search: Assertion `!(thread != atoms->thread)' failed

Changing the sort function to use thread object pointers together with pid and
tid check. This way new thread will never find old one with same pid/tid.

Link: http://lkml.kernel.org/n/tip-o4doazhhv0zax5zshkg8hnys@git.kernel.org
Reported-by: Mohit Agrawal <moagrawa@...hat.com>
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
Acked-by: Namhyung Kim <namhyung@...nel.org>
Cc: David Ahern <dsahern@...il.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/1446462625-15807-1-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/builtin-sched.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 0ee6d90..e3d3e32 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -1203,12 +1203,13 @@ static void output_lat_thread(struct perf_sched *sched, struct work_atoms *work_
 
 static int pid_cmp(struct work_atoms *l, struct work_atoms *r)
 {
+	if (l->thread == r->thread)
+		return 0;
 	if (l->thread->tid < r->thread->tid)
 		return -1;
 	if (l->thread->tid > r->thread->tid)
 		return 1;
-
-	return 0;
+	return (int)(l->thread - r->thread);
 }
 
 static int avg_cmp(struct work_atoms *l, struct work_atoms *r)
--
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