[PATCH] vt: refactor console SAK processing
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>
diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c
index dc8368e..3a5d301 100644
--- a/drivers/char/vt_ioctl.c
+++ b/drivers/char/vt_ioctl.c
@@ -672,7 +672,8 @@
vc->vt_mode = tmp;
/* the frsig is ignored, so we set it to 0 */
vc->vt_mode.frsig = 0;
- put_pid(xchg(&vc->vt_pid, get_pid(task_pid(current))));
+ put_pid(vc->vt_pid);
+ vc->vt_pid = get_pid(task_pid(current));
/* no switch is required -- saw@shade.msu.ru */
vc->vt_newvt = -1;
release_console_sem();
@@ -1063,12 +1064,35 @@
vc->vt_mode.relsig = 0;
vc->vt_mode.acqsig = 0;
vc->vt_mode.frsig = 0;
- put_pid(xchg(&vc->vt_pid, NULL));
+ put_pid(vc->vt_pid);
+ vc->vt_pid = NULL;
vc->vt_newvt = -1;
if (!in_interrupt()) /* Via keyboard.c:SAK() - akpm */
reset_palette(vc);
}
+void vc_SAK(struct work_struct *work)
+{
+ struct vc *vc_con =
+ container_of(work, struct vc, SAK_work);
+ struct vc_data *vc;
+ struct tty_struct *tty;
+
+ acquire_console_sem();
+ vc = vc_con->d;
+ if (vc) {
+ tty = vc->vc_tty;
+ /*
+ * SAK should also work in all raw modes and reset
+ * them properly.
+ */
+ if (tty)
+ __do_SAK(tty);
+ reset_vc(vc);
+ }
+ release_console_sem();
+}
+
/*
* Performs the back end of a vt switch
*/