Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/drzeus/mmc

[linux-2.6] / drivers / char / vt_ioctl.c

diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c
index 3a5d301e783b062617f3e7043b42670e33ca2be2..7a61a2a9aafe3879dc8a0e443fd7d1379e7e493e 100644 (file)
--- a/drivers/char/vt_ioctl.c
+++ b/drivers/char/vt_ioctl.c
@@ -34,7 +34,7 @@
 #include <linux/kbd_diacr.h>
 #include <linux/selection.h>
 
-static char vt_dont_switch;
+char vt_dont_switch;
 extern struct tty_driver *console_driver;
 
 #define VT_IS_IN_USE(i)        (console_driver->ttys[i] && console_driver->ttys[i]->count)
@@ -770,6 +770,7 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
                /*
                 * Switching-from response
                 */
+               acquire_console_sem();
                if (vc->vt_newvt >= 0) {
                        if (arg == 0)
                                /*
@@ -784,7 +785,6 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
                                 * complete the switch.
                                 */
                                int newvt;
-                               acquire_console_sem();
                                newvt = vc->vt_newvt;
                                vc->vt_newvt = -1;
                                i = vc_allocate(newvt);
@@ -798,7 +798,6 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
                                 * other console switches..
                                 */
                                complete_change_console(vc_cons[newvt].d);
-                               release_console_sem();
                        }
                }
 
@@ -810,9 +809,12 @@ int vt_ioctl(struct tty_struct *tty, struct file * file,
                        /*
                         * If it's just an ACK, ignore it
                         */
-                       if (arg != VT_ACKACQ)
+                       if (arg != VT_ACKACQ) {
+                               release_console_sem();
                                return -EINVAL;
+                       }
                }
+               release_console_sem();
 
                return 0;
 
@@ -1030,7 +1032,7 @@ static DECLARE_WAIT_QUEUE_HEAD(vt_activate_queue);
 
 /*
  * Sleeps until a vt is activated, or the task is interrupted. Returns
- * 0 if activation, -EINTR if interrupted.
+ * 0 if activation, -EINTR if interrupted by a signal handler.
  */
 int vt_waitactive(int vt)
 {
@@ -1039,17 +1041,29 @@ int vt_waitactive(int vt)
 
        add_wait_queue(&vt_activate_queue, &wait);
        for (;;) {
-               set_current_state(TASK_INTERRUPTIBLE);
                retval = 0;
-               if (vt == fg_console)
+
+               /*
+                * Synchronize with redraw_screen(). By acquiring the console
+                * semaphore we make sure that the console switch is completed
+                * before we return. If we didn't wait for the semaphore, we
+                * could return at a point where fg_console has already been
+                * updated, but the console switch hasn't been completed.
+                */
+               acquire_console_sem();
+               set_current_state(TASK_INTERRUPTIBLE);
+               if (vt == fg_console) {
+                       release_console_sem();
                        break;
-               retval = -EINTR;
+               }
+               release_console_sem();
+               retval = -ERESTARTNOHAND;
                if (signal_pending(current))
                        break;
                schedule();
        }
        remove_wait_queue(&vt_activate_queue, &wait);
-       current->state = TASK_RUNNING;
+       __set_current_state(TASK_RUNNING);
        return retval;
 }
 
@@ -1196,15 +1210,18 @@ void change_console(struct vc_data *new_vc)
                /*
                 * Send the signal as privileged - kill_pid() will
                 * tell us if the process has gone or something else
-                * is awry
+                * is awry.
+                *
+                * We need to set vt_newvt *before* sending the signal or we
+                * have a race.
                 */
+               vc->vt_newvt = new_vc->vc_num;
                if (kill_pid(vc->vt_pid, vc->vt_mode.relsig, 1) == 0) {
                        /*
                         * It worked. Mark the vt to switch to and
                         * return. The process needs to send us a
                         * VT_RELDISP ioctl to complete the switch.
                         */
-                       vc->vt_newvt = new_vc->vc_num;
                        return;
                }