From: Stephane Eranian <[email protected]> This patch fixes a problem with perf stat whereby on termination it may send a SIGTERM signal to random processes on systems with high PID recycling. I got some actual bug reports on this.
There is race between the SIGCHLD and sig_atexit() handlers. This patch addresses this problem by clearing child_pid in the SIGCHLD handler. Signed-off-by: Stephane Eranian <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Namhyung Kim <[email protected]> Cc: Peter Zijlstra <[email protected]> Link: http://lkml.kernel.org/r/20130604154426.GA2928@quad Signed-off-by: Arnaldo Carvalho de Melo <[email protected]> --- tools/perf/builtin-stat.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index 7e910ba..95768af 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -87,7 +87,7 @@ static int run_count = 1; static bool no_inherit = false; static bool scale = true; static enum aggr_mode aggr_mode = AGGR_GLOBAL; -static pid_t child_pid = -1; +static volatile pid_t child_pid = -1; static bool null_run = false; static int detailed_run = 0; static bool big_num = true; @@ -1148,13 +1148,34 @@ static void skip_signal(int signo) done = 1; signr = signo; + /* + * render child_pid harmless + * won't send SIGTERM to a random + * process in case of race condition + * and fast PID recycling + */ + child_pid = -1; } static void sig_atexit(void) { + sigset_t set, oset; + + /* + * avoid race condition with SIGCHLD handler + * in skip_signal() which is modifying child_pid + * goal is to avoid send SIGTERM to a random + * process + */ + sigemptyset(&set); + sigaddset(&set, SIGCHLD); + sigprocmask(SIG_BLOCK, &set, &oset); + if (child_pid != -1) kill(child_pid, SIGTERM); + sigprocmask(SIG_SETMASK, &oset, NULL); + if (signr == -1) return; -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
