Commit ce3b642d authored by Jeff Dike's avatar Jeff Dike Committed by Linus Torvalds

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 for the

This patch works around it by blocking SIGIO while the terminal attributes are
being fiddled.
Signed-off-by: default avatarJeff Dike <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 0a765329
......@@ -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)) {
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;
return -errno;
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