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uml: work around host tcsetattr bug

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Under the conditions that UML uses it, tcgetattr is guaranteed to return
-EINTR when the console is attached to /dev/ptmx, making generic_console_write
hang because it loops, calling tcgetattr until it succeeds.  This is a host
bug - see http://marc.info/?l=linux-kernel&m=119618990807182&w=2 for the
details.

This patch works around it by blocking SIGIO while the terminal attributes are
being fiddled.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jeff Dike 2007-12-01 12:16:30 -08:00 committed by Linus Torvalds
parent 0a765329ed
commit ce3b642d42
1 changed files with 10 additions and 1 deletions
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11
arch/um/drivers/chan_user.c
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@ -74,10 +74,16 @@ void generic_free(void *data)
int generic_console_write(int fd, const char *buf, int n)
{
sigset_t old, no_sigio;
struct termios save, new;
int err;
if (isatty(fd)) {
sigemptyset(&no_sigio);
sigaddset(&no_sigio, SIGIO);
if (sigprocmask(SIG_BLOCK, &no_sigio, &old))
goto error;
CATCH_EINTR(err = tcgetattr(fd, &save));
if (err)
goto error;
@ -97,8 +103,11 @@ int generic_console_write(int fd, const char *buf, int n)
* Restore raw mode, in any case; we *must* ignore any error apart
* EINTR, except for debug.
*/
if (isatty(fd))
if (isatty(fd)) {
CATCH_EINTR(tcsetattr(fd, TCSAFLUSH, &save));
sigprocmask(SIG_SETMASK, &old, NULL);
}
return err;
error:
return -errno;