lkml.org 
[lkml]   [2014]   [Jun]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH tty-next 09/22] tty: Remove tty_hung_up_p() tests from tty drivers' open()
On Mon, Jun 16, 2014 at 09:17:06AM -0400, Peter Hurley wrote:
> 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>

For the CRIS part:

Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>

> CC: Samuel Ortiz <samuel@sortiz.org>
> CC: "David S. Miller" <davem@davemloft.net>
> Signed-off-by: Peter Hurley <peter@hurleysoftware.com>

/^JN - Jesper Nilsson
--
Jesper Nilsson -- jesper.nilsson@axis.com


\
 
 \ /
  Last update: 2014-06-16 16:41    [W:2.025 / U:0.428 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site