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authorRabin Vincent <rabin.vincent@stericsson.com>2012-05-21 13:38:42 +0530
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-06-14 17:10:08 -0700
commit2fc46915ecfbc51afcf995901f6ade7c3d503a25 (patch)
tree8b7b2a931020acdd349e2eb793f4e8da85239d37 /drivers/tty/vt
parent057eb856eda1d957c0f1155eaa90739221f809a7 (diff)
downloadop-kernel-dev-2fc46915ecfbc51afcf995901f6ade7c3d503a25.zip
op-kernel-dev-2fc46915ecfbc51afcf995901f6ade7c3d503a25.tar.gz
vt: fix race in vt_waitactive()
pm_restore_console() is called from the suspend/resume path, and this calls vt_move_to_console(), which calls vt_waitactive(). There's a race in this path which causes the process which requests the suspend to sleep indefinitely waiting for an event which already happened: P1 P2 vt_move_to_console() set_console() schedule_console_callback() vt_waitactive() check n == fg_console +1 console_callback() switch_screen() vt_event_post() // no waiters vt_event_wait() // forever Fix the race by ensuring we're registered for the event before we check if it's already completed. Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com> Acked-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/vt')
-rw-r--r--drivers/tty/vt/vt_ioctl.c47
1 files changed, 34 insertions, 13 deletions
diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index 6461854..b841f56 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -110,16 +110,7 @@ void vt_event_post(unsigned int event, unsigned int old, unsigned int new)
wake_up_interruptible(&vt_event_waitqueue);
}
-/**
- * vt_event_wait - wait for an event
- * @vw: our event
- *
- * Waits for an event to occur which completes our vt_event_wait
- * structure. On return the structure has wv->done set to 1 for success
- * or 0 if some event such as a signal ended the wait.
- */
-
-static void vt_event_wait(struct vt_event_wait *vw)
+static void __vt_event_queue(struct vt_event_wait *vw)
{
unsigned long flags;
/* Prepare the event */
@@ -129,8 +120,18 @@ static void vt_event_wait(struct vt_event_wait *vw)
spin_lock_irqsave(&vt_event_lock, flags);
list_add(&vw->list, &vt_events);
spin_unlock_irqrestore(&vt_event_lock, flags);
+}
+
+static void __vt_event_wait(struct vt_event_wait *vw)
+{
/* Wait for it to pass */
wait_event_interruptible(vt_event_waitqueue, vw->done);
+}
+
+static void __vt_event_dequeue(struct vt_event_wait *vw)
+{
+ unsigned long flags;
+
/* Dequeue it */
spin_lock_irqsave(&vt_event_lock, flags);
list_del(&vw->list);
@@ -138,6 +139,22 @@ static void vt_event_wait(struct vt_event_wait *vw)
}
/**
+ * vt_event_wait - wait for an event
+ * @vw: our event
+ *
+ * Waits for an event to occur which completes our vt_event_wait
+ * structure. On return the structure has wv->done set to 1 for success
+ * or 0 if some event such as a signal ended the wait.
+ */
+
+static void vt_event_wait(struct vt_event_wait *vw)
+{
+ __vt_event_queue(vw);
+ __vt_event_wait(vw);
+ __vt_event_dequeue(vw);
+}
+
+/**
* vt_event_wait_ioctl - event ioctl handler
* @arg: argument to ioctl
*
@@ -177,10 +194,14 @@ int vt_waitactive(int n)
{
struct vt_event_wait vw;
do {
- if (n == fg_console + 1)
- break;
vw.event.event = VT_EVENT_SWITCH;
- vt_event_wait(&vw);
+ __vt_event_queue(&vw);
+ if (n == fg_console + 1) {
+ __vt_event_dequeue(&vw);
+ break;
+ }
+ __vt_event_wait(&vw);
+ __vt_event_dequeue(&vw);
if (vw.done == 0)
return -EINTR;
} while (vw.event.newev != n);
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