linux.git/drivers/char/pty.c, branch v2.6.32

headers: remove sched.h from interrupt.h

2009-10-11T18:20:58+00:00

After m68k's task_thread_info() doesn't refer to current,
it's possible to remove sched.h from interrupt.h and not break m68k!
Many thanks to Heiko Carstens for allowing this.

Signed-off-by: Alexey Dobriyan

pty: reconnect the BSD TIOCSPTLCK handling to legacy ptys

2009-09-30T14:49:40+00:00

David Howells noticed (due to the compiler warning about an unused
'pty_ops_bsd' variable) that we haven't actually been using the code
that implements TIOCSPTLCK for legacy pty handling.  It's been that way
since 2.6.26, commit 3e8e88ca053150efdbecb45d8f481cf560ec808d to be
exact ("pty: prepare for tty->ops changes").

DavidH initially submitted a patch just removing the dead code entirely,
and since nobody has apparently ever complained, I'm not entirely sure
that wouldn't be the right thing to do.  But since the whole and only
point of the legacy pty code is to be compatible with legacy distros
that don't use the new unix98 pty model, let's just wire it up again.

And clean it up a bit while we're at it.

Acked-by: David Howells 
Cc: Alan Cox 
Signed-off-by: Linus Torvalds

pty_write: don't do a tty_wakeup() when the buffers are full

2009-09-18T14:05:58+00:00

Commit ac89a9174 ("pty: don't limit the writes to 'pty_space()' inside
'pty_write()'") removed the pty_space() checking, in order to let the
regular tty buffer code limit the buffering itself.

That was all good, but as a subtle side effect it meant that we'd be
doing a tty_wakeup() even in the case where the buffers were all filled
up, and didn't actually make any progress on the write.

Which sounds innocuous, but it interacts very badly with the ppp_async
code, which has an infinite loop in ppp_async_push() that tries to push
out data to the tty.  When we call tty_wakeup(), that loop ends up
thinking that progress was made (see the subtle interactions between
XMIT_WAKEUP and 'tty_stuffed' for details).  End result: one unhappy ppp
user.

Fixed by noticing when tty_insert_flip_string() didn't actually do
anything, and then not doing any more processing (including, very much
not calling tty_wakeup()).

Bisected-and-tested-by: Peter Volkov 
Cc: stable@kernel.org (2.6.31)
Signed-off-by: Linus Torvalds

pty: don't limit the writes to 'pty_space()' inside 'pty_write()'

2009-09-05T20:27:10+00:00

The whole write-room thing is something that is up to the _caller_ to
worry about, not the pty layer itself.  The total buffer space will
still be limited by the buffering routines themselves, so there is no
advantage or need in having pty_write() artificially limit the size
somehow.

And what happened was that the caller (the n_tty line discipline, in
this case) may have verified that there is room for 2 bytes to be
written (for NL -> CRNL expansion), and it used to then do those writes
as two single-byte writes.  And if the first byte written (CR) then
caused a new tty buffer to be allocated, pty_space() may have returned
zero when trying to write the second byte (LF), and then incorrectly
failed the write - leading to a lost newline character.

This should finally fix

	http://bugzilla.kernel.org/show_bug.cgi?id=14015

Reported-by: Mikael Pettersson 
Acked-by: Alan Cox 
Signed-off-by: Linus Torvalds

pty: fix data loss when stopped (^S/^Q)

2009-08-10T20:31:18+00:00

Commit d945cb9cc ("pty: Rework the pty layer to use the normal buffering
logic") dropped the test for 'tty->stopped' in pty_write_room(), which
then causes the n_tty line discipline thing to not throttle the data
properly when the tty is stopped.

So instead of pausing the write due to the tty being stopped, the ldisc
layer would go ahead and push it down to the pty.  The pty write()
routine would then refuse to take the data (because it _did_ check
'stopped'), and the data wouldn't actually be written.

This whole stopped test should eventually be moved into the tty ldisc
layer rather than have low-level tty drivers care about these things,
but right now the fix is to just re-instate the missing pty 'stopped'
handling.

Reported-and-tested-by: Artur Skawina 
Cc: Alan Cox 
Signed-off-by: Linus Torvalds

pty: avoid forcing 'low_latency' tty flag

2009-07-29T19:15:56+00:00

We really don't want to mark the pty as a low-latency device, because as
Alan points out, the ->write method can be called from an IRQ (ppp?),
and that means we can't use ->low_latency=1 as we take mutexes in the
low_latency case.

So rather than using low_latency to force the written data to be pushed
to the ldisc handling at 'write()' time, just make the reader side (or
the poll function) do the flush when it checks whether there is data to
be had.

This also fixes the problem with lost data in an emacs compile buffer
(bugzilla 13815), and we can thus revert the low_latency pty hack
(commit 3a54297478e6578f96fd54bf4daa1751130aca86: "pty: quickfix for the
pty ENXIO timing problems").

Signed-off-by: OGAWA Hirofumi 
Tested-by: Aneesh Kumar K.V 
[ Modified to do the tty_flush_to_ldisc() inside input_available_p() so
  that it triggers for both read and poll()  - Linus]
Signed-off-by: Linus Torvalds

pty: quickfix for the pty ENXIO timing problems

2009-07-27T22:53:29+00:00

This also makes close stall in the normal case which is apparently
needed to fix emacs

Signed-off-by: Alan Cox 
Signed-off-by: Linus Torvalds

headers: smp_lock.h redux

2009-07-12T19:22:34+00:00

* Remove smp_lock.h from files which don't need it (including some headers!)
* Add smp_lock.h to files which do need it
* Make smp_lock.h include conditional in hardirq.h
  It's needed only for one kernel_locked() usage which is under CONFIG_PREEMPT

  This will make hardirq.h inclusion cheaper for every PREEMPT=n config
  (which includes allmodconfig/allyesconfig, BTW)

Signed-off-by: Alexey Dobriyan 
Signed-off-by: Linus Torvalds

pty: Rework the pty layer to use the normal buffering logic

2009-07-08T16:47:59+00:00

This fixes the ppp problems and various other issues with call locking
caused by one side of a pty called in one locking context trying to match
another with differing rules on the other side. We also get a big slack
space to work with that means we can bury the flow control deadlock case
for any conceivable real world situation.

Signed-off-by: Alan Cox 
Signed-off-by: Linus Torvalds

pty: Narrow the race on ldisc locking

2009-06-16T19:01:16+00:00

The pty code has always been buggy on its ldisc handling. The recent
changes made the window for the race much bigger. Pending fixing it
properly which is not at all trivial, at least make the race small again so
we don't disrupt other dev work.

Signed-off-by: Alan Cox 
Signed-off-by: Linus Torvalds