uml: work around host tcsetattr bug (ce3b642d) · Commits · 戴 / test

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>

arch/um/drivers/chan_user.c

+10 −1

Original line number	Diff line number	Diff line
		@@ -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;

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