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 /drivers/tty/serial/crisv10.c | |
| 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 'drivers/tty/serial/crisv10.c')
| -rw-r--r-- | drivers/tty/serial/crisv10.c | 15 |
1 files changed, 5 insertions, 10 deletions
diff --git a/drivers/tty/serial/crisv10.c b/drivers/tty/serial/crisv10.c index d567ac5d3af4..58e6f61a87e4 100644 --- a/drivers/tty/serial/crisv10.c +++ b/drivers/tty/serial/crisv10.c @@ -3831,14 +3831,13 @@ block_til_ready(struct tty_struct *tty, struct file * filp, DECLARE_WAITQUEUE(wait, current); unsigned long flags; int retval; - int do_clocal = 0, extra_count = 0; + int do_clocal = 0; /* * If the device is in the middle of being closed, then block * until it's done, and then try again. */ - 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)); #ifdef SERIAL_DO_RESTART @@ -3879,10 +3878,7 @@ block_til_ready(struct tty_struct *tty, struct file * filp, info->line, info->port.count); #endif local_irq_save(flags); - if (!tty_hung_up_p(filp)) { - extra_count++; - info->port.count--; - } + info->port.count--; local_irq_restore(flags); info->port.blocked_open++; while (1) { @@ -3921,7 +3917,7 @@ block_til_ready(struct tty_struct *tty, struct file * filp, } set_current_state(TASK_RUNNING); remove_wait_queue(&info->port.open_wait, &wait); - if (extra_count) + if (!tty_hung_up_p(filp)) info->port.count++; info->port.blocked_open--; #ifdef SERIAL_DEBUG_OPEN @@ -3976,8 +3972,7 @@ rs_open(struct tty_struct *tty, struct file * filp) /* * If the port is in 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)); #ifdef SERIAL_DO_RESTART |