From 5cb73340d92a716fd2776700742c3558206ae298 Mon Sep 17 00:00:00 2001 From: Adrian Hunter Date: Wed, 19 Aug 2015 17:29:20 +0300 Subject: [PATCH] perf tools: Make fork event processing more resilient When processing a fork event, the tools lookup the parent thread by its tid. In a couple of cases, it is possible for that thread to have the wrong pid. That can happen if the data is being processed out of order, or if the (fork) event that would have removed the erroneous thread was lost. Assume the latter case, print a dump message, remove the erroneous thread, create a new one with the correct pid, and keep going. Reported-by: Arnaldo Carvalho de Melo Signed-off-by: Adrian Hunter Tested-by: Jiri Olsa Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1439994561-27436-3-git-send-email-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/machine.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index 7ff682770fdb..f1a4c833121e 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -1387,6 +1387,24 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event event->fork.ptid); int err = 0; + if (dump_trace) + perf_event__fprintf_task(event, stdout); + + /* + * There may be an existing thread that is not actually the parent, + * either because we are processing events out of order, or because the + * (fork) event that would have removed the thread was lost. Assume the + * latter case and continue on as best we can. + */ + if (parent->pid_ != (pid_t)event->fork.ppid) { + dump_printf("removing erroneous parent thread %d/%d\n", + parent->pid_, parent->tid); + machine__remove_thread(machine, parent); + thread__put(parent); + parent = machine__findnew_thread(machine, event->fork.ppid, + event->fork.ptid); + } + /* if a thread currently exists for the thread id remove it */ if (thread != NULL) { machine__remove_thread(machine, thread); @@ -1395,8 +1413,6 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event thread = machine__findnew_thread(machine, event->fork.pid, event->fork.tid); - if (dump_trace) - perf_event__fprintf_task(event, stdout); if (thread == NULL || parent == NULL || thread__fork(thread, parent, sample->time) < 0) {