linux-kernel - Re: Deadlock in fb and tty

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Date:	Thu, 12 Sep 2013 06:22:24 -0700 (PDT)
From:	johnflux <johnflux@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: Deadlock in fb and tty

The following seems to be better:

>From d93c1e9761ff66365d658da7d8d0d33823aa946f Mon Sep 17 00:00:00 2001
From: John Tapsell <johnflux@...il.com>
Date: Thu, 12 Sep 2013 09:16:12 +0100
Subject: [PATCH] Fix deadlock between fb_info and console.  Do not lock
 fb_info when calling sending the FB_EVENT_CONBLANK

In fbmem.c, the semantics are that we acquire the lock_fb_info first,
and then console_lock.  However when fbcon.c fbcon_generic_blank() is
called, the console lock could already be held.  Locking fb_info can
thus cause a deadlock.

fbmem.c sends the FB_EVENT_BLANK without locking lock_fb_info first, so
this change introduces similar behaviour.
---
 drivers/video/console/fbcon.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index 6b4fb5c..8546441 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -2333,13 +2333,9 @@ static void fbcon_generic_blank(struct vc_data *vc,
struct fb_info *info,
                vc->vc_video_erase_char = oldc;
        }
 
-
-       if (!lock_fb_info(info))
-               return;
        event.info = info;
        event.data = &blank;
        fb_notifier_call_chain(FB_EVENT_CONBLANK, &event);
-       unlock_fb_info(info);
 }
 
 static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch)
-- 
1.8.1.2


How can I get this reviewed/acked please?



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