[lttng-dev] [PATCH lttng-tools] Fix: ignore SIGPIPE

[Jérémie Galarneau]

Merged, thanks!

Jérémie

On 6 October 2016 at 12:57, Mathieu Desnoyers
<mathieu.desnoyers at efficios.com> wrote:
> 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 at efficios.com>
> ---
>  src/bin/lttng-consumerd/lttng-consumerd.c | 12 +++---------
>  src/bin/lttng-relayd/main.c               | 11 +++++------
>  src/bin/lttng-sessiond/main.c             | 11 +++++------
>  3 files changed, 13 insertions(+), 21 deletions(-)
>
> diff --git a/src/bin/lttng-consumerd/lttng-consumerd.c b/src/bin/lttng-consumerd/lttng-consumerd.c
> index 1636b9c..1373a74 100644
> --- 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 e8f3087..ea46ec7 100644
> --- 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 1964fe0..a2afb8f 100644
> --- 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;
>         }
> --
> 2.1.4
>



-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com