fix spinlock recursion in hvc_console

commit 611e097d7707741a336a0677d9d69bec40f29f3d
Author: Christian Borntraeger <borntraeger@de.ibm.com>
hvc_console: rework setup to replace irq functions with callbacks
introduced a spinlock recursion problem.

request_irq tries to call the handler if the IRQ is shared.
The irq handler of hvc_console calls hvc_poll and hvc_kill
which might take the hvc_struct spinlock. Therefore, we have
to call request_irq outside the spinlock.

We can move the notifier_add safely outside the spinlock as ->data must
not be changed by the backend. Otherwise, tty_hangup would fail anyway.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 2 insertions, 3 deletions

diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c
index 02aac104842d..fd64137b1ab9 100644
--- a/drivers/char/hvc_console.c
+++ b/drivers/char/hvc_console.c
@@ -322,11 +322,10 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
 
         hp->tty = tty;
 
-        if (hp->ops->notifier_add)
-                rc = hp->ops->notifier_add(hp, hp->data);
-
         spin_unlock_irqrestore(&hp->lock, flags);
 
+        if (hp->ops->notifier_add)
+                rc = hp->ops->notifier_add(hp, hp->data);
 
         /*
          * If the notifier fails we return an error.  The tty layer