diff options
| author | Dmitry Safonov <dima@arista.com> | 2018-11-01 00:24:48 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-12-17 20:38:37 +0100 |
| commit | ebded7823e7f1aedf9d8b47a5cb006119895a9d2 (patch) | |
| tree | f331dc68675feaf3d90ec8e7a619a83e2264b19d /drivers/tty/tty_ldisc.c | |
| parent | b7b8d8e667d0e5b4074bdb68e0faed2218b764de (diff) | |
tty: Don't block on IO when ldisc change is pending
[ Upstream commit c96cf923a98d1b094df9f0cf97a83e118817e31b ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.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 01fcdc7ff077..62dd2abb57fe 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -348,6 +348,11 @@ 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; @@ -358,6 +363,8 @@ 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); } |