Fix: ignore SIGPIPE

Issuing fprintf() to stderr (thus write() to the standard error file
descriptor) within the SIGPIPE signal handler is bad: it can trigger
SIGPIPE repeatedly if the listening end has closed its end of the pipe.

Set the SIGPIPE action to SIG_IGN in relayd, sessiond, and consumerd.

This was affecting sessiond and relayd. The consumerd did not print
anything to stderr.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/bin/lttng-consumerd/lttng-consumerd.c b/src/bin/lttng-consumerd/lttng-consumerd.c
index 1636b9c0d22777798ff220df010c4bc5ca6c9634..1373a74b28212d5595d8c4f0dc18a89938e6a616 100644 (file)
--- a/src/bin/lttng-consumerd/lttng-consumerd.c
+++ b/src/bin/lttng-consumerd/lttng-consumerd.c
@@ -99,14 +99,6 @@ static void sighandler(int sig)
                return;
        }
 
-       /*
-        * Ignore SIGPIPE because it should not stop the consumer whenever a
-        * SIGPIPE is caught through a FD operation.
-        */
-       if (sig == SIGPIPE) {
-               return;
-       }
-
        if (ctx) {
                lttng_consumer_should_exit(ctx);
        }
@@ -127,9 +119,10 @@ static int set_signal_handler(void)
                return ret;
        }
 
-       sa.sa_handler = sighandler;
        sa.sa_mask = sigset;
        sa.sa_flags = 0;
+
+       sa.sa_handler = sighandler;
        if ((ret = sigaction(SIGTERM, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
@@ -140,6 +133,7 @@ static int set_signal_handler(void)
                return ret;
        }
 
+       sa.sa_handler = SIG_IGN;
        if ((ret = sigaction(SIGPIPE, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;

diff --git a/src/bin/lttng-relayd/main.c b/src/bin/lttng-relayd/main.c
index e8f3087b11bd95e966be7e4e5c9dcf9ad1eb5a1e..ea46ec72276117359b32fa499b584357b5aeb401 100644 (file)
--- a/src/bin/lttng-relayd/main.c
+++ b/src/bin/lttng-relayd/main.c
@@ -582,9 +582,6 @@ int lttng_relay_stop_threads(void)
 static void sighandler(int sig)
 {
        switch (sig) {
-       case SIGPIPE:
-               DBG("SIGPIPE caught");
-               return;
        case SIGINT:
                DBG("SIGINT caught");
                if (lttng_relay_stop_threads()) {
@@ -620,9 +617,10 @@ static int set_signal_handler(void)
                return ret;
        }
 
-       sa.sa_handler = sighandler;
        sa.sa_mask = sigset;
        sa.sa_flags = 0;
+
+       sa.sa_handler = sighandler;
        if ((ret = sigaction(SIGTERM, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
@@ -633,12 +631,13 @@ static int set_signal_handler(void)
                return ret;
        }
 
-       if ((ret = sigaction(SIGPIPE, &sa, NULL)) < 0) {
+       if ((ret = sigaction(SIGUSR1, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }
 
-       if ((ret = sigaction(SIGUSR1, &sa, NULL)) < 0) {
+       sa.sa_handler = SIG_IGN;
+       if ((ret = sigaction(SIGPIPE, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }

diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c
index 1964fe0cca3b80e57b8293d00aa12cfb92d18790..a2afb8f757626b71f24655d7b682ac38c483a019 100644 (file)
--- a/src/bin/lttng-sessiond/main.c
+++ b/src/bin/lttng-sessiond/main.c
@@ -5370,9 +5370,6 @@ error:
 static void sighandler(int sig)
 {
        switch (sig) {
-       case SIGPIPE:
-               DBG("SIGPIPE caught");
-               return;
        case SIGINT:
                DBG("SIGINT caught");
                stop_threads();
@@ -5404,9 +5401,10 @@ static int set_signal_handler(void)
                return ret;
        }
 
-       sa.sa_handler = sighandler;
        sa.sa_mask = sigset;
        sa.sa_flags = 0;
+
+       sa.sa_handler = sighandler;
        if ((ret = sigaction(SIGTERM, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
@@ -5417,12 +5415,13 @@ static int set_signal_handler(void)
                return ret;
        }
 
-       if ((ret = sigaction(SIGPIPE, &sa, NULL)) < 0) {
+       if ((ret = sigaction(SIGUSR1, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }
 
-       if ((ret = sigaction(SIGUSR1, &sa, NULL)) < 0) {
+       sa.sa_handler = SIG_IGN;
+       if ((ret = sigaction(SIGPIPE, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }