From 58a06a6dfb11121bc1220c1c21fdf11ae65ac895 Mon Sep 17 00:00:00 2001
From: Michal Schmidt <mschmidt@redhat.com>
Date: Sun, 18 Dec 2011 14:57:54 +0100
Subject: [PATCH] log: never block on syslog in PID 1

Use a non-blocking syslog socket if logging from PID 1.
If sendmsg fails with EAGAIN, fall back to kmsg or console only for the
current message. Next message will try syslog again.
(cherry picked from commit 8f7f7a1bd3a26f501b2d6546cce1c669b59dcc87)
---
 src/log.c |   23 ++++++++++++++++-------
 1 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/src/log.c b/src/log.c
index 5c5b734..4f57821 100644
--- a/src/log.c
+++ b/src/log.c
@@ -118,6 +118,9 @@ static int create_log_socket(int type) {
         struct timeval tv;
         int fd;
 
+        if (getpid() == 1)
+                /* systemd should not block on syslog */
+                type |= SOCK_NONBLOCK;
         if ((fd = socket(AF_UNIX, type|SOCK_CLOEXEC, 0)) < 0)
                 return -errno;
 
@@ -330,7 +333,8 @@ static int write_to_syslog(
         for (;;) {
                 ssize_t n;
 
-                if ((n = sendmsg(syslog_fd, &msghdr, MSG_NOSIGNAL)) < 0)
+                n = sendmsg(syslog_fd, &msghdr, MSG_NOSIGNAL);
+                if (n < 0)
                         return -errno;
 
                 if (!syslog_is_stream ||
@@ -407,8 +411,10 @@ static int log_dispatch(
                     log_target == LOG_TARGET_SYSLOG_OR_KMSG ||
                     log_target == LOG_TARGET_SYSLOG) {
 
-                        if ((k = write_to_syslog(level, file, line, func, buffer)) < 0) {
-                                log_close_syslog();
+                        k = write_to_syslog(level, file, line, func, buffer);
+                        if (k < 0) {
+                                if (k != -EAGAIN)
+                                        log_close_syslog();
                                 log_open_kmsg();
                         } else if (k > 0)
                                 r++;
@@ -419,16 +425,19 @@ static int log_dispatch(
                      log_target == LOG_TARGET_SYSLOG_OR_KMSG ||
                      log_target == LOG_TARGET_KMSG)) {
 
-                        if ((k = write_to_kmsg(level, file, line, func, buffer)) < 0) {
+                        k = write_to_kmsg(level, file, line, func, buffer);
+                        if (k < 0) {
                                 log_close_kmsg();
                                 log_open_console();
                         } else if (k > 0)
                                 r++;
                 }
 
-                if (k <= 0 &&
-                    (k = write_to_console(level, file, line, func, buffer)) < 0)
-                        return k;
+                if (k <= 0) {
+                        k = write_to_console(level, file, line, func, buffer);
+                        if (k < 0)
+                                return k;
+                }
 
                 buffer = e;
         } while (buffer);