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

From: tip-bot for Jiri Olsa
Date: Sun Nov 08 2015 - 02:31:44 EST

Commit-ID: 0014de172d228e450377d1fd079d94e67128d27f
Gitweb: http://git.kernel.org/tip/0014de172d228e450377d1fd079d94e67128d27f
Author: Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Mon, 2 Nov 2015 12:10:25 +0100
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
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@xxxxxxxxxxxxxx
Reported-by: Mohit Agrawal <moagrawa@xxxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Acked-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1446462625-15807-1-git-send-email-jolsa@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
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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