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From 3665e8094e50f1f70b02a34d96c005ce152d62a6 Mon Sep 17 00:00:00 2001
From: Colin Watson <cjwatson@ubuntu.com>
Date: Sat, 20 Nov 2010 17:57:22 +0100
Subject: [PATCH] Retry opening console device on EIO
As reported in https://launchpad.net/bugs/544139, ConsoleKit sometimes fails to
track the active VT. This particular case was tracked down to a race condition
that happens if you try to open /dev/console while the current TTY is currently
being closed. This yields an -EIO error, in which case CK should just try
again.
For a more detailled summary of the problem from a kernel perspective, please
see https://bugs.launchpad.net/ubuntu/+source/linux/+bug/554172/comments/245 .
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=31790
Bug-Ubuntu: https://launchpad.net/bugs/544139
---
src/ck-sysdeps-unix.c | 17 +++++++++++++++++
1 files changed, 17 insertions(+), 0 deletions(-)
diff --git a/src/ck-sysdeps-unix.c b/src/ck-sysdeps-unix.c
index e4ab16b..4a1736c 100644
--- a/src/ck-sysdeps-unix.c
+++ b/src/ck-sysdeps-unix.c
@@ -26,6 +26,7 @@
#include <unistd.h>
#include <string.h>
#include <errno.h>
+#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
@@ -150,9 +151,25 @@ open_a_console (char *fnam)
{
int fd;
+again:
fd = open (fnam, O_RDONLY | O_NOCTTY);
if (fd < 0 && errno == EACCES)
fd = open (fnam, O_WRONLY | O_NOCTTY);
+#ifdef __linux__
+ if (fd < 0 && errno == EIO) {
+ /* Linux can return EIO if the tty is currently closing,
+ * which can happen if multiple processes are opening and
+ * closing the console in parallel. Unfortunately it can
+ * also return EIO in more serious situations too (see
+ * https://bugs.launchpad.net/bugs/554172), but there isn't
+ * much we can do about that since we really need a console
+ * fd.
+ */
+ struct timespec ts = { 0, 100000000 }; /* 0.1 seconds */
+ nanosleep (&ts, NULL);
+ goto again;
+ }
+#endif
if (fd < 0)
return -1;
--
1.7.2.3
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