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author | Peter Hurley <peter@hurleysoftware.com> | 2014-06-16 09:17:06 -0400 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-07-10 16:06:49 -0700 |
commit | e359a4e38d229d53e28905863a1fabf41debd591 (patch) | |
tree | c70f7762dac31dad62188b7b8bb2140bea8b311a /drivers/tty/cyclades.c | |
parent | 5fda7a0e715c32c6dd9a39ebce8429eeafb64b7d (diff) | |
download | linux-e359a4e38d229d53e28905863a1fabf41debd591.tar.gz |
tty: Remove tty_hung_up_p() tests from tty drivers' open()
Since at least before 2.6.30, it has not been possible to observe a hung up file pointer in a tty driver's open() method unless/until the driver open() releases the tty_lock() (eg., before blocking). This is because tty_open() adds the file pointer while holding the tty_lock() _and_ doesn't release the lock until after calling the tty driver's open() method. [ Before tty_lock(), this was lock_kernel(). ] Since __tty_hangup() first waits on the tty_lock() before enumerating and hanging up the open file pointers, either __tty_hangup() will wait for the tty_lock() or tty_open() will not yet have added the file pointer. For example, CPU 0 | CPU 1 | tty_open | __tty_hangup .. | .. tty_lock | .. tty_reopen | tty_lock / blocks .. | tty_add_file(tty, filp) | .. | tty->ops->open(tty, filp) | tty_port_open | tty_port_block_til_ready | .. | while (1) | .. | tty_unlock | / unblocks schedule | for each filp on tty->tty_files | f_ops = tty_hung_up_fops; | .. | tty_unlock tty_lock | .. | tty_unlock | Note that since tty_port_block_til_ready() and similar drop the tty_lock while blocking, when woken, the file pointer must then be tested for having been hung up. Also, fix bit-rotted drivers that used extra_count to track the port->count bump. CC: Mikael Starvik <starvik@axis.com> CC: Samuel Ortiz <samuel@sortiz.org> CC: "David S. Miller" <davem@davemloft.net> Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Acked-by: Jesper Nilsson <jesper.nilsson@axis.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/cyclades.c')
-rw-r--r-- | drivers/tty/cyclades.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/tty/cyclades.c b/drivers/tty/cyclades.c index a57bb5ab761c..fd66f57390d0 100644 --- a/drivers/tty/cyclades.c +++ b/drivers/tty/cyclades.c @@ -1579,7 +1579,7 @@ static int cy_open(struct tty_struct *tty, struct file *filp) /* * If the port is the middle of closing, bail out now */ - if (tty_hung_up_p(filp) || (info->port.flags & ASYNC_CLOSING)) { + if (info->port.flags & ASYNC_CLOSING) { wait_event_interruptible_tty(tty, info->port.close_wait, !(info->port.flags & ASYNC_CLOSING)); return (info->port.flags & ASYNC_HUP_NOTIFY) ? -EAGAIN: -ERESTARTSYS; |