From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Tue, 29 Sep 2015 16:19:00 +0000 (-0400)
Subject: Fix: Log and ignore SIGINT and SIGTERM in run_as worker
X-Git-Tag: v2.7.1~13
X-Git-Url: http://git.lttng.org./?a=commitdiff_plain;h=8ce28af8cd87de4cbbe2ee2fe490b9abff807ab7;p=lttng-tools.git

Fix: Log and ignore SIGINT and SIGTERM in run_as worker

The run_as worker is in the same process group as its parent and
will receive both SIGINT and SIGTERM. However, we want to give
the worker a chance to tear itself down gracefully when its
parent closes the command socket.

The run_as worker will now ignore these signals (although it will
log them) and wait for the parent to induce the teardown.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/common/runas.c b/src/common/runas.c
index 08979fb79..fc30a5567 100644
--- a/src/common/runas.c
+++ b/src/common/runas.c
@@ -528,9 +528,9 @@ int run_as_rmdir_recursive(const char *path, uid_t uid, gid_t gid)
 }
 
 static
-void reset_sighandler(void)
+int reset_sighandler(void)
 {
-	int sig;
+	int sig, ret = 0;
 
 	for (sig = SIGHUP; sig <= SIGUNUSED; sig++) {
 		/* Skip unblockable signals. */
@@ -539,8 +539,67 @@ void reset_sighandler(void)
 		}
 		if (signal(sig, SIG_DFL) == SIG_ERR) {
 			PERROR("reset signal %d", sig);
+			ret = -1;
+			goto end;
 		}
 	}
+end:
+	return ret;
+}
+
+static
+void worker_sighandler(int sig)
+{
+	const char *signame;
+
+	/*
+	 * The worker will its parent's signals since they are part of the same
+	 * process group. However, in the case of SIGINT and SIGTERM, we want
+	 * to give the worker a chance to teardown gracefully when its parent
+	 * closes the command socket.
+	 */
+	switch (sig) {
+	case SIGINT:
+		signame = "SIGINT";
+		break;
+	case SIGTERM:
+		signame = "SIGTERM";
+		break;
+	default:
+		signame = "Unknown";
+	}
+
+	DBG("run_as worker received signal %s", signame);
+}
+
+static
+int set_worker_sighandlers(void)
+{
+	int ret = 0;
+	sigset_t sigset;
+	struct sigaction sa;
+
+	if ((ret = sigemptyset(&sigset)) < 0) {
+		PERROR("sigemptyset");
+		goto end;
+	}
+
+	sa.sa_handler = worker_sighandler;
+	sa.sa_mask = sigset;
+	sa.sa_flags = 0;
+	if ((ret = sigaction(SIGINT, &sa, NULL)) < 0) {
+		PERROR("sigaction SIGINT");
+		goto end;
+	}
+
+	if ((ret = sigaction(SIGTERM, &sa, NULL)) < 0) {
+		PERROR("sigaction SIGTERM");
+		goto end;
+	}
+
+	DBG("run_as signal handler set for SIGTERM and SIGINT");
+end:
+	return ret;
 }
 
 LTTNG_HIDDEN
@@ -584,6 +643,8 @@ int run_as_create_worker(char *procname)
 
 		reset_sighandler();
 
+		set_worker_sighandlers();
+
 		/* The child has no use for this lock. */
 		pthread_mutex_unlock(&worker_lock);
 		/* Just close, no shutdown. */