diff options
| author |   Peter Hurley <peter@hurleysoftware.com> | 2014-06-16 09:17:06 -0400 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-07-10 16:06:49 -0700 |
| commit | e359a4e38d229d53e28905863a1fabf41debd591 (patch) | |
| tree | c70f7762dac31dad62188b7b8bb2140bea8b311a /drivers/char/pcmcia | |
| parent | serial: Use UPF_* constants with struct uart_port flags (diff) | |
| download | linux-dev-e359a4e38d229d53e28905863a1fabf41debd591.tar.xz linux-dev-e359a4e38d229d53e28905863a1fabf41debd591.zip | |
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/char/pcmcia')
| -rw-r--r-- | drivers/char/pcmcia/synclink_cs.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/char/pcmcia/synclink_cs.c b/drivers/char/pcmcia/synclink_cs.c index 8320abd1ef14..a63970f76967 100644 --- a/drivers/char/pcmcia/synclink_cs.c +++ b/drivers/char/pcmcia/synclink_cs.c @@ -2510,7 +2510,7 @@ static int mgslpc_open(struct tty_struct *tty, struct file * filp) __FILE__, __LINE__, tty->driver->name, port->count); /* If port is closing, signal caller to try again */ - if (tty_hung_up_p(filp) || port->flags & ASYNC_CLOSING){ + if (port->flags & ASYNC_CLOSING){ wait_event_interruptible_tty(tty, port->close_wait, !(port->flags & ASYNC_CLOSING)); retval = ((port->flags & ASYNC_HUP_NOTIFY) ? |