diff options
| author | Dmitry Safonov <dima@arista.com> | 2018-11-01 01:24:48 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-12-05 12:16:33 +0100 |
| commit | c96cf923a98d1b094df9f0cf97a83e118817e31b (patch) | |
| tree | 600f4d868ef87ff58a642bb7e6d4825894d9c657 /drivers/tty/tty_ldisc.c | |
| parent | tty: Hold tty_ldisc_lock() during tty_reopen() (diff) | |
| download | linux-c96cf923a98d1b094df9f0cf97a83e118817e31b.tar.xz 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/tty_ldisc.c')
| -rw-r--r-- | drivers/tty/tty_ldisc.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index fc4c97cae01e..9434d20cf3ca 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -327,6 +327,11 @@ int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) { int ret; + /* Kindly asking blocked readers to release the read side */ + set_bit(TTY_LDISC_CHANGING, &tty->flags); + wake_up_interruptible_all(&tty->read_wait); + wake_up_interruptible_all(&tty->write_wait); + ret = __tty_ldisc_lock(tty, timeout); if (!ret) return -EBUSY; @@ -337,6 +342,8 @@ int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) void tty_ldisc_unlock(struct tty_struct *tty) { clear_bit(TTY_LDISC_HALTED, &tty->flags); + /* Can be cleared here - ldisc_unlock will wake up writers firstly */ + clear_bit(TTY_LDISC_CHANGING, &tty->flags); __tty_ldisc_unlock(tty); } |