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[PATCH] vt: refactor console SAK processing

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This does several things.
- It moves looking up of the current foreground console into process
  context where we can safely take the semaphore that protects this
  operation.
- It uses the new flavor of work queue processing.
- This generates a factor of do_SAK, __do_SAK that runs immediately.
- This calls __do_SAK with the console semaphore held ensuring nothing
  else happens to the console while we process the SAK operation.
- With the console SAK processing moved into process context this
  patch removes the xchg operations that I used to attempt to attomically
  update struct pid, because of the strange locking used in the SAK processing.
  With SAK using the normal console semaphore nothing special is needed.

Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Eric W. Biederman
2007-02-10 01:44:34 -08:00
committed by Linus Torvalds
parent 0a7b35cb18
commit 8b6312f4dc
6 changed files with 45 additions and 18 deletions
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13
drivers/char/tty_io.c
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@@ -3324,10 +3324,8 @@ int tty_ioctl(struct inode * inode, struct file * file,
* Nasty bug: do_SAK is being called in interrupt context. This can
* deadlock. We punt it up to process context. AKPM - 16Mar2001
*/
static void __do_SAK(struct work_struct *work)
void __do_SAK(struct tty_struct *tty)
{
struct tty_struct *tty =
container_of(work, struct tty_struct, SAK_work);
#ifdef TTY_SOFT_SAK
tty_hangup(tty);
#else
@@ -3394,6 +3392,13 @@ static void __do_SAK(struct work_struct *work)
#endif
}
static void do_SAK_work(struct work_struct *work)
{
struct tty_struct *tty =
container_of(work, struct tty_struct, SAK_work);
__do_SAK(tty);
}
/*
* The tq handling here is a little racy - tty->SAK_work may already be queued.
* Fortunately we don't need to worry, because if ->SAK_work is already queued,
@@ -3404,7 +3409,7 @@ void do_SAK(struct tty_struct *tty)
{
if (!tty)
return;
PREPARE_WORK(&tty->SAK_work, __do_SAK);
PREPARE_WORK(&tty->SAK_work, do_SAK_work);
schedule_work(&tty->SAK_work);
}