perf tools: Don't stop synthesizing threads when one vanishes

The perf_event__synthesize_threads routine synthesizes all the existing
threads in the system, because we don't have any kernel facilities to
ask for PERF_RECORD_{FORK,MMAP,COMM} for existing threads.

It was returning an error as soon as one thread couldn't be synthesized,
which is a bit extreme when, for instance, a forkish workload is
running, like a kernel compile.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-i7oas1eodpoer2bx38fwyasv@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 6 insertions, 7 deletions

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 0ae444ef1429..ca9ca285406a 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -405,16 +405,15 @@ int perf_event__synthesize_threads(struct perf_tool *tool,
 
                 if (*end) /* only interested in proper numerical dirents */
                         continue;
-
-                if (__event__synthesize_thread(comm_event, mmap_event, pid, 1,
-                                           process, tool, machine) != 0) {
-                        err = -1;
-                        goto out_closedir;
-                }
+                /*
+                 * We may race with exiting thread, so don't stop just because
+                 * one thread couldn't be synthesized.
+                 */
+                __event__synthesize_thread(comm_event, mmap_event, pid, 1,
+                                           process, tool, machine);
         }
 
         err = 0;
-out_closedir:
         closedir(proc);
 out_free_mmap:
         free(mmap_event);