Messages in this thread Patch in this message | | | Date | Wed, 28 Nov 2007 14:04:40 -0500 | From | Jeff Dike <> | Subject | [PATCH 4/4] UML - Work around host tcsetattr bug |
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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; - 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/
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