uml: work around host tcsetattr bug
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>
diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c
index b88e93b..0257640 100644
--- a/arch/um/drivers/chan_user.c
+++ b/arch/um/drivers/chan_user.c
@@ -74,10 +74,16 @@
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 @@
* 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;