Patch "perf evlist: Reference count the cpu and thread maps at set_maps()" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

perf evlist: Reference count the cpu and thread maps at set_maps()

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
perf-evlist-reference-count-the-cpu-and-thread-maps-at-set_maps.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Arnaldo Carvalho de Melo <[email protected]>
Date: Wed, 17 Feb 2016 10:57:19 -0300
Subject: perf evlist: Reference count the cpu and thread maps at set_maps()

From: Arnaldo Carvalho de Melo <[email protected]>

commit a55e5663761366fb883f6f25375dd68bc958b9db upstream.

We were dropping the reference we possibly held but not obtaining one for the new maps, which we will drop at perf_evlist__delete(), fix it.

This was caught by Steven Noonan in some of the machines which would produce this output when caught by glibc debug mechanisms:

  $ sudo perf test 21
  21: Test object code reading                                 :***
  Error in `perf': corrupted double-linked list: 0x00000000023ffcd0 ***
  ======= Backtrace: =========
  /usr/lib/libc.so.6(+0x72055)[0x7f25be0f3055]
  /usr/lib/libc.so.6(+0x779b6)[0x7f25be0f89b6]
  /usr/lib/libc.so.6(+0x7a0ed)[0x7f25be0fb0ed]
  /usr/lib/libc.so.6(__libc_calloc+0xba)[0x7f25be0fceda]
  perf(parse_events_lex_init_extra+0x38)[0x4cfff8]
  perf(parse_events+0x55)[0x4a0615]
  perf(perf_evlist__config+0xcf)[0x4eeb2f]
  perf[0x479f82]
  perf(test__code_reading+0x1e)[0x47ad4e]
  perf(cmd_test+0x5dd)[0x46452d]
  perf[0x47f4e3]
  perf(main+0x603)[0x42c723]
  /usr/lib/libc.so.6(__libc_start_main+0xf0)[0x7f25be0a1610]
  perf(_start+0x29)[0x42c859]

Further investigation using valgrind led to the reference count imbalance fixed in this patch.

Report-Link: http://lkml.kernel.org/r/CAKbGBLjC2Dx5vshxyGmQkcD+VwiAQLbHoXA9i7kvRB2-2opHZQ@mail.gmail.com

---
 tools/perf/util/evlist.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -1211,12 +1211,12 @@ void perf_evlist__set_maps(struct perf_e
 	 */
 	if (cpus != evlist->cpus) {
 		cpu_map__put(evlist->cpus);
-		evlist->cpus = cpus;
+		evlist->cpus = cpu_map__get(cpus);
 	}
 
 	if (threads != evlist->threads) {
 		thread_map__put(evlist->threads);
-		evlist->threads = threads;
+		evlist->threads = thread_map__get(threads);
 	}
 
 	perf_evlist__propagate_maps(evlist);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/perf-evlist-reference-count-the-cpu-and-thread-maps-at-set_maps.patch queue-4.4/perf-intel-pt-fix-segfault-tracing-transactions.patch