perf stat: Avoid sending SIGTERM to random processes (d07f0b12) · Commits · 戴 / test

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 <eranian@google.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20130604154426.GA2928@quad Signed-off-by:

Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-stat.c

+22 −1

Original line number	Diff line number	Diff line
		@@ -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;

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