Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759258AbXK1TGY (ORCPT ); Wed, 28 Nov 2007 14:06:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755989AbXK1TFj (ORCPT ); Wed, 28 Nov 2007 14:05:39 -0500 Received: from saraswathi.solana.com ([198.99.130.12]:42877 "EHLO saraswathi.solana.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759444AbXK1TFh (ORCPT ); Wed, 28 Nov 2007 14:05:37 -0500 Date: Wed, 28 Nov 2007 14:04:40 -0500 From: Jeff Dike To: Andrew Morton Cc: LKML , uml-devel Subject: [PATCH 4/4] UML - Work around host tcsetattr bug Message-ID: <20071128190440.GA8313@c2.user-mode-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.2.3i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1821 Lines: 54 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 --- arch/um/drivers/chan_user.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) Index: linux-2.6.22/arch/um/drivers/chan_user.c =================================================================== --- linux-2.6.22.orig/arch/um/drivers/chan_user.c 2007-11-21 11:43:50.000000000 -0500 +++ linux-2.6.22/arch/um/drivers/chan_user.c 2007-11-27 14:03:10.000000000 -0500 @@ -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 * 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; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/