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| author | Dmitry Safonov <dima@arista.com> | 2018-11-01 00:24:48 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-12-05 12:16:33 +0100 |
| commit | c96cf923a98d1b094df9f0cf97a83e118817e31b (patch) | |
| tree | 600f4d868ef87ff58a642bb7e6d4825894d9c657 /drivers/tty/n_tty.c | |
| parent | 83d817f41070c48bc3eb7ec18e43000a548fca5c (diff) | |
| download | linux-c96cf923a98d1b094df9f0cf97a83e118817e31b.tar.gz linux-c96cf923a98d1b094df9f0cf97a83e118817e31b.tar.bz2 linux-c96cf923a98d1b094df9f0cf97a83e118817e31b.zip | |
tty: Don't block on IO when ldisc change is pending
There might be situations where tty_ldisc_lock() has blocked, but there
is already IO on tty and it prevents line discipline changes.
It might theoretically turn into dead-lock.
Basically, provide more priority to pending tty_ldisc_lock() than to
servicing reads/writes over tty.
User-visible issue was reported by Mikulas where on pa-risc with
Debian 5 reboot took either 80 seconds, 3 minutes or 3:25 after proper
locking in tty_reopen().
Cc: Jiri Slaby <jslaby@suse.com>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/n_tty.c')
| -rw-r--r-- | drivers/tty/n_tty.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 3ad460219fd6..5dc9686697cf 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -1702,7 +1702,7 @@ n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp, down_read(&tty->termios_rwsem); - while (1) { + do { /* * When PARMRK is set, each input char may take up to 3 chars * in the read buf; reduce the buffer space avail by 3x @@ -1744,7 +1744,7 @@ n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp, fp += n; count -= n; rcvd += n; - } + } while (!test_bit(TTY_LDISC_CHANGING, &tty->flags)); tty->receive_room = room; @@ -2211,7 +2211,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, break; if (!timeout) break; - if (file->f_flags & O_NONBLOCK) { + if (tty_io_nonblock(tty, file)) { retval = -EAGAIN; break; } @@ -2365,7 +2365,7 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, } if (!nr) break; - if (file->f_flags & O_NONBLOCK) { + if (tty_io_nonblock(tty, file)) { retval = -EAGAIN; break; } |