Messages in this thread |  | | Date | Wed, 18 Feb 2015 09:58:06 -0500 | From | Aristeu Rozanski <> | Subject | Re: [PATCH] n_tty_read: check for hanging tty while waiting for input |
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Hi Peter, On Tue, Feb 17, 2015 at 05:35:10PM -0500, Peter Hurley wrote: > I realize that. But hanging up the tty that is /dev/console only affects > open descriptors that are not /dev/console. > > So readers using the /dev/ttyS0 file descriptor will see a hungup fops, > but readers using /dev/console will not, and /dev/ttyS0 will _not_ > be closed or released because of the still-open descriptor on /dev/console.
I see.
> Ok, so the process sleeping on /dev/console read() should have received > SIGHUP, which would wake the process and cause it to exit the > n_tty_read() loop, thus dropping the ldisc reference it holds. > Did it ignore the signal or perhaps the signal is masked?
Not masked on the test case (attached). Sent sighup manually and it did receive it.
-- Aristeu
#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <termios.h> #include <errno.h> #include <signal.h> #include <sys/types.h> #include <sys/stat.h> #include <sys/wait.h> #include <fcntl.h> #include <sys/ioctl.h>
static char *default_console = "/dev/console"; static char *default_tty = "/dev/ttyS0"; struct data { char *console; char *tty; };
static void *reader(void *d) { struct data *data = (struct data *)d; struct termios old_termio; char buff[512]; int fd = -1, rc;
while (1) { if (fd == -1) { fd = open(data->console, O_RDWR); if (fd < 0) exit(1); if (tcgetattr(fd, &old_termio) == -1) exit(1); old_termio.c_lflag = ICANON; if (tcsetattr(fd, 0, &old_termio) == -1) exit(1); } rc = read(fd, buff, sizeof(buff)); if (rc < 0 && errno == EAGAIN) continue; close(fd); fd = -1; } }
void launch(void *(*fn)(void *), struct data *data) { if (fork() == 0) fn(data); }
int main(int argc, char *argv[]) { struct data data; int fd;
fd = open("/dev/ttyS0", O_RDWR); close(0); close(1); close(2); ioctl(fd, TIOCSCTTY, 1);
data.console = default_console; data.tty = default_tty;
launch(reader, &data);
waitpid(-1, NULL, 0);
return 0; }
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