diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2015-10-10 23:00:51 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-10-18 07:11:29 +0300 |
| commit | 79c1faa4511e78380cd643dac88a775062a08bc0 (patch) | |
| tree | 71d15bef9323d929a02d2f04d184ef2f7614b92e /drivers/tty/hvc | |
| parent | 32ede4a51754cb62b0d43d91cb7c4e3c57069a9c (diff) | |
| download | linux-79c1faa4511e78380cd643dac88a775062a08bc0.tar.xz | |
tty: Remove tty_wait_until_sent_from_close()
tty_wait_until_sent_from_close() drops the tty lock while waiting
for the tty driver to finish sending previously accepted data (ie.,
data remaining in its write buffer and transmit fifo).
tty_wait_until_sent_from_close() was added by commit a57a7bf3fc7e
("TTY: define tty_wait_until_sent_from_close") to prevent the entire
tty subsystem from being unable to open new ttys while waiting for
one tty to close while output drained.
However, since commit 0911261d4cb6 ("tty: Don't take tty_mutex for tty
count changes"), holding a tty lock while closing does not prevent other
ttys from being opened/closed/hung up, but only prevents lifetime event
changes for the tty under lock.
Holding the tty lock while waiting for output to drain does prevent
parallel non-blocking opens (O_NONBLOCK) from advancing or returning
while the tty lock is held. However, all parallel opens _already_
block even if the tty lock is dropped while closing and the parallel
open advances. Blocking in open has been in mainline since at least 2.6.29
(see tty_port_block_til_ready(); note the test for O_NONBLOCK is _after_
the wait while ASYNC_CLOSING).
IOW, before this patch a non-blocking open will sleep anyway for the
_entire_ duration of a parallel hardware shutdown, and when it wakes, the
error return will cause a release of its tty, and it will restart with
a fresh attempt to open. Similarly with a blocking open that is already
waiting; when it's woken, the hardware shutdown has already completed
to ASYNC_INITIALIZED is not set, which forces a release and restart as
well.
So, holding the tty lock across the _entire_ close (which is what this
patch does), even while waiting for output to drain, is equivalent to
the current outcome wrt parallel opens.
Cc: Alan Cox <alan@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
CC: Arnd Bergmann <arnd@arndb.de>
CC: Karsten Keil <isdn@linux-pingi.de>
CC: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/hvc')
| -rw-r--r-- | drivers/tty/hvc/hvc_console.c | 2 | ||||
| -rw-r--r-- | drivers/tty/hvc/hvcs.c | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c index 9c30f67c802a..e46d628998f5 100644 --- a/drivers/tty/hvc/hvc_console.c +++ b/drivers/tty/hvc/hvc_console.c @@ -418,7 +418,7 @@ static void hvc_close(struct tty_struct *tty, struct file * filp) * there is no buffered data otherwise sleeps on a wait queue * waking periodically to check chars_in_buffer(). */ - tty_wait_until_sent_from_close(tty, HVC_CLOSE_WAIT); + tty_wait_until_sent(tty, HVC_CLOSE_WAIT); } else { if (hp->port.count < 0) printk(KERN_ERR "hvc_close %X: oops, count is %d\n", diff --git a/drivers/tty/hvc/hvcs.c b/drivers/tty/hvc/hvcs.c index f7ff97c0ad34..5997b1731111 100644 --- a/drivers/tty/hvc/hvcs.c +++ b/drivers/tty/hvc/hvcs.c @@ -1230,7 +1230,7 @@ static void hvcs_close(struct tty_struct *tty, struct file *filp) irq = hvcsd->vdev->irq; spin_unlock_irqrestore(&hvcsd->lock, flags); - tty_wait_until_sent_from_close(tty, HVCS_CLOSE_WAIT); + tty_wait_until_sent(tty, HVCS_CLOSE_WAIT); /* * This line is important because it tells hvcs_open that this |