diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2014-06-16 15:17:06 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-07-11 01:06:49 +0200 |
| commit | e359a4e38d229d53e28905863a1fabf41debd591 (patch) | |
| tree | c70f7762dac31dad62188b7b8bb2140bea8b311a /net | |
| parent | serial: Use UPF_* constants with struct uart_port flags (diff) | |
| download | linux-e359a4e38d229d53e28905863a1fabf41debd591.tar.xz linux-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 'net')
| -rw-r--r-- | net/irda/ircomm/ircomm_tty.c | 6 |
1 files changed, 2 insertions, 4 deletions
diff --git a/net/irda/ircomm/ircomm_tty.c b/net/irda/ircomm/ircomm_tty.c index 2ba8b9705bb7..61ceb4cdb4a2 100644 --- a/net/irda/ircomm/ircomm_tty.c +++ b/net/irda/ircomm/ircomm_tty.c @@ -320,8 +320,7 @@ static int ircomm_tty_block_til_ready(struct ircomm_tty_cb *self, __FILE__, __LINE__, tty->driver->name, port->count); spin_lock_irqsave(&port->lock, flags); - if (!tty_hung_up_p(filp)) - port->count--; + port->count--; port->blocked_open++; spin_unlock_irqrestore(&port->lock, flags); @@ -458,8 +457,7 @@ static int ircomm_tty_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) || - test_bit(ASYNCB_CLOSING, &self->port.flags)) { + if (test_bit(ASYNCB_CLOSING, &self->port.flags)) { /* Hm, why are we blocking on ASYNC_CLOSING if we * do return -EAGAIN/-ERESTARTSYS below anyway? |