From: Jeff Dike <jdike@addtoit.com>
To: Andrew Morton <akpm@osdl.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
uml-devel <user-mode-linux-devel@lists.sourceforge.net>
Subject: [uml-devel] [PATCH 4/4] UML - Work around host tcsetattr bug
Date: Wed, 28 Nov 2007 14:04:40 -0500 [thread overview]
Message-ID: <20071128190440.GA8313@c2.user-mode-linux.org> (raw)
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>
---
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;
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WARNING: multiple messages have this Message-ID (diff)
From: Jeff Dike <jdike@addtoit.com>
To: Andrew Morton <akpm@osdl.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
uml-devel <user-mode-linux-devel@lists.sourceforge.net>
Subject: [PATCH 4/4] UML - Work around host tcsetattr bug
Date: Wed, 28 Nov 2007 14:04:40 -0500 [thread overview]
Message-ID: <20071128190440.GA8313@c2.user-mode-linux.org> (raw)
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>
---
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;
next reply other threads:[~2007-11-28 19:04 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-28 19:04 Jeff Dike [this message]
2007-11-28 19:04 ` [PATCH 4/4] UML - Work around host tcsetattr bug Jeff Dike
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