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author | Linus Torvalds <torvalds@linux-foundation.org> | 2009-10-03 21:44:21 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-10-03 21:44:21 -0700 |
commit | 0b5759c654e74c8dc317ea2c6b3a7476160f688a (patch) | |
tree | 50de6ba41dcc19cb76c8a35408b7cc1ba80d2e41 /arch/arm/mm/copypage-xscale.c | |
parent | f0a221ef47df3cdde2123fe75ce3b61bb7df656d (diff) |
tty: Avoid dropping ldisc_mutex over hangup tty re-initialization
A couple of people have hit the WARN_ON() in drivers/char/tty_io.c,
tty_open() that is unhappy about seeing the tty line discipline go away
during the tty hangup. See for example
http://bugzilla.kernel.org/show_bug.cgi?id=14255
and the reason is that we do the tty_ldisc_halt() outside the
ldisc_mutex in order to be able to flush the scheduled work without a
deadlock with vhangup_work.
However, it turns out that we can solve this particular case by
- using "cancel_delayed_work_sync()" in tty_ldisc_halt(), which waits
for just the particular work, rather than synchronizing with any
random outstanding pending work.
This won't deadlock, since the buf.work we synchronize with doesn't
care about the ldisc_mutex, it just flushes the tty ldisc buffers.
- realize that for this particular case, we don't need to wait for any
hangup work, because we are inside the hangup codepaths ourselves.
so as a result we can just drop the flush_scheduled_work() entirely, and
then move the tty_ldisc_halt() call to inside the mutex. That way we
never expose the partially torn down ldisc state to tty_open(), and hold
the ldisc_mutex over the whole sequence.
Reported-by: Ingo Molnar <mingo@elte.hu>
Reported-by: Heinz Diehl <htd@fancy-poultry.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/arm/mm/copypage-xscale.c')
0 files changed, 0 insertions, 0 deletions