Re: Deadlock in fb and tty
From: Peter Hurley
Date: Tue Sep 17 2013 - 15:09:32 EST
On 09/12/2013 09:22 AM, johnflux wrote:
The following seems to be better:
From d93c1e9761ff66365d658da7d8d0d33823aa946f Mon Sep 17 00:00:00 2001
From: John Tapsell<johnflux@xxxxxxxxx>
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 = ␣
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?
The get_maintainer.pl script can help to discover to whom to
address patches. For example,
peter@thor:~/src/kernels/next$ ./scripts/get_maintainer.pl -f drivers/video/console/fbcon.c
Jean-Christophe Plagniol-Villard <plagnioj@xxxxxxxxxxxx> (maintainer:FRAMEBUFFER LAYER)
Tomi Valkeinen <tomi.valkeinen@xxxxxx> (maintainer:FRAMEBUFFER LAYER)
Dave Airlie <airlied@xxxxxxxxxx> (commit_signer:5/11=45%)
Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> (commit_signer:4/11=36%)
Wang YanQing <udknight@xxxxxxxxx> (commit_signer:4/11=36%)
Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> (commit_signer:3/11=27%)
Kamal Mostafa <kamal@xxxxxxxxxx> (commit_signer:1/11=9%)
linux-fbdev@xxxxxxxxxxxxxxx (open list:FRAMEBUFFER LAYER)
linux-kernel@xxxxxxxxxxxxxxx (open list)
In this case, you'll want to send this patch addressed to the two maintainers
and cc linux-fbdev and linux-kernel. You can cc me if you want.
This is covered in Documentation/SubmittingPatches, which also covers the
required subject line format <hint: too long, needs subsystem identifier>.
Also, if you have the lockdep report of the deadlock, it's customary to
include it in the commit message.
Regards,
Peter Hurley
PS - Don't put stuff after the '--' tag at the end of the patch. Many
mailers treat that as don't care. I missed your question first time around
because Thunderbird grays that text :(
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