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[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>
This commit is contained in:
Bodo Stroesser 2005-09-03 15:57:24 -07:00 committed by Linus Torvalds
parent 0221575903
commit ed1b58d8b5
1 changed files with 6 additions and 5 deletions
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11
arch/um/drivers/chan_user.c
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@ -63,7 +63,7 @@ error:
* *
* SIGWINCH can't be received synchronously, so you have to set up to receive it * 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 * 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). * it (see below for how we make sure to exit only on SIGWINCH).
*/ */
@ -94,18 +94,19 @@ static int winch_thread(void *arg)
"byte, err = %d\n", -count); "byte, err = %d\n", -count);
/* We are not using SIG_IGN on purpose, so don't fix it as I thought to /* 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. */ * SIGWINCH. */
signal(SIGWINCH, winch_handler); signal(SIGWINCH, winch_handler);
sigfillset(&sigs); sigfillset(&sigs);
sigdelset(&sigs, SIGWINCH); /* Block all signals possible. */
/* Block anything else than SIGWINCH. */
if(sigprocmask(SIG_SETMASK, &sigs, NULL) < 0){ if(sigprocmask(SIG_SETMASK, &sigs, NULL) < 0){
printk("winch_thread : sigprocmask failed, errno = %d\n", printk("winch_thread : sigprocmask failed, errno = %d\n",
errno); errno);
exit(1); exit(1);
} }
/* In sigsuspend(), block anything else than SIGWINCH. */
sigdelset(&sigs, SIGWINCH);
if(setsid() < 0){ if(setsid() < 0){
printk("winch_thread : setsid failed, errno = %d\n", errno); printk("winch_thread : setsid failed, errno = %d\n", errno);
@ -130,7 +131,7 @@ static int winch_thread(void *arg)
while(1){ while(1){
/* This will be interrupted by SIGWINCH only, since other signals /* This will be interrupted by SIGWINCH only, since other signals
* are blocked.*/ * are blocked.*/
pause(); sigsuspend(&sigs);
count = os_write_file(pipe_fd, &c, sizeof(c)); count = os_write_file(pipe_fd, &c, sizeof(c));
if(count != sizeof(c)) if(count != sizeof(c))