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authorPeter Hurley <peter@hurleysoftware.com>2015-10-10 16:00:51 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-10-17 21:11:29 -0700
commit79c1faa4511e78380cd643dac88a775062a08bc0 (patch)
tree71d15bef9323d929a02d2f04d184ef2f7614b92e /drivers/tty/hvc
parent32ede4a51754cb62b0d43d91cb7c4e3c57069a9c (diff)
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.c2
-rw-r--r--drivers/tty/hvc/hvcs.c2
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