From f173657bccae4dd0cbfe0a7ed33ebc9117b74f05 Mon Sep 17 00:00:00 2001

From: Lennart Poettering <lennart@poettering.net>

Date: Wed, 24 Jul 2013 07:24:05 +0200

Subject: [PATCH] core: synchronously block when logging

Previously, the logging sockets were asynchronous and if clogged we'd

lose messages. We did this to be extra careful given that PID 1 might

need to spawn the logging daemon as response to PID 1's own log messages

and we really should avoid a deadlock in that case.

As it turns out this causes loss of too many messages, hence make the

socket blocking again, however put a time limit on it to avoid unbounded

deadlocks in the unlikely case they happen.

https://bugs.freedesktop.org/show_bug.cgi?id=66664

---

 src/shared/log.c | 12 ++++++++----

 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/shared/log.c b/src/shared/log.c

index 27317f7..8f4995a 100644

--- a/src/shared/log.c

+++ b/src/shared/log.c

@@ -115,16 +115,20 @@ void log_close_syslog(void) {

 static int create_log_socket(int type) {

         int fd;

+        struct timeval tv;

-        /* All output to the syslog/journal fds we do asynchronously,

-         * and if the buffers are full we just drop the messages */

-

-        fd = socket(AF_UNIX, type|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);

+        fd = socket(AF_UNIX, type|SOCK_CLOEXEC, 0);

         if (fd < 0)

                 return -errno;

         fd_inc_sndbuf(fd, SNDBUF_SIZE);

+        /* We need a blocking fd here since we'd otherwise lose

+        messages way too early. However, let's not hang forever in the

+        unlikely case of a deadlock. */

+        timeval_store(&tv, 1*USEC_PER_MINUTE);

+        setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv));

+

         return fd;

 }