[PATCH] uml: fix SIGWINCH handler race while waiting for signals.
If a SIGWINCH comes in, while winch_thread() isn't waiting in wait(),
winch_thread could miss signals. It isn't very probable, that anyone will
see this causing trouble, as it would need a very special timing, that a
missed SIGWINCH results in a wrong window size.
So, this is a minor problem. But why not fix, as it can be done so easy?
Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c
index 5d37681..de3bce7 100644
--- a/arch/um/drivers/chan_user.c
+++ b/arch/um/drivers/chan_user.c
@@ -63,7 +63,7 @@
*
* SIGWINCH can't be received synchronously, so you have to set up to receive it
* as a signal. That being the case, if you are going to wait for it, it is
- * convenient to sit in a pause() and wait for the signal to bounce you out of
+ * convenient to sit in sigsuspend() and wait for the signal to bounce you out of
* it (see below for how we make sure to exit only on SIGWINCH).
*/
@@ -94,18 +94,19 @@
"byte, err = %d\n", -count);
/* We are not using SIG_IGN on purpose, so don't fix it as I thought to
- * do! If using SIG_IGN, the pause() call below would not stop on
+ * do! If using SIG_IGN, the sigsuspend() call below would not stop on
* SIGWINCH. */
signal(SIGWINCH, winch_handler);
sigfillset(&sigs);
- sigdelset(&sigs, SIGWINCH);
- /* Block anything else than SIGWINCH. */
+ /* Block all signals possible. */
if(sigprocmask(SIG_SETMASK, &sigs, NULL) < 0){
printk("winch_thread : sigprocmask failed, errno = %d\n",
errno);
exit(1);
}
+ /* In sigsuspend(), block anything else than SIGWINCH. */
+ sigdelset(&sigs, SIGWINCH);
if(setsid() < 0){
printk("winch_thread : setsid failed, errno = %d\n", errno);
@@ -130,7 +131,7 @@
while(1){
/* This will be interrupted by SIGWINCH only, since other signals
* are blocked.*/
- pause();
+ sigsuspend(&sigs);
count = os_write_file(pipe_fd, &c, sizeof(c));
if(count != sizeof(c))