On Wed, Jun 15, 2011 at 7:58 AM, Bruno Prémont <bonbons@xxxxxxxxxxxxxxxxx> wrote: > Hi, > > On Wed, 15 Jun 2011 09:09:24 Wanlong Gao <wanlong.gao@xxxxxxxxx> wrote: >> <snip> >> Hi Francis: >> can you test this patch? > > Do you have a deadlock trace which you are trying to fix? > > It's either the caller of unregister_framebuffer() which must be > changed to not call unregister_framebuffer with info's lock held or > the code reacting on the notification that must not try to acquire the > lock again. > > The interesting par is if console semaphore has some relation to this > deadlock as the order for taking both varies... It could be > lock_fb_info(); console_lock() versus console_lock(); lock_fb_info() > > Bruno > > >> Thanks >> >> From fe026c42af4cbdce053460a428a445e99071586a Mon Sep 17 00:00:00 2001 >> From: Wanlong Gao <wanlong.gao@xxxxxxxxx> >> Date: Wed, 15 Jun 2011 09:03:41 +0800 >> Subject: [PATCH] test >> >> >> >> Signed-off-by: Wanlong Gao <wanlong.gao@xxxxxxxxx> >> --- >> drivers/video/fbmem.c | 3 --- >> 1 files changed, 0 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c >> index 5aac00e..6e6cef3 100644 >> --- a/drivers/video/fbmem.c >> +++ b/drivers/video/fbmem.c >> @@ -1642,11 +1642,8 @@ static int do_unregister_framebuffer(struct >> fb_info *fb_info) >> if (i < 0 || i >= FB_MAX || registered_fb[i] != fb_info) >> return -EINVAL; >> >> - if (!lock_fb_info(fb_info)) >> - return -ENODEV; >> event.info = fb_info; >> ret = fb_notifier_call_chain(FB_EVENT_FB_UNBIND, &event); >> - unlock_fb_info(fb_info); > > Not a good idea to stop taking fb_lock here. > Pretty all calls of fb_notifier_call_chain are protected by info's > lock, except the one for FB_EVENT_FB_UNREGISTERED a few lines further. > > IMHO it wou make sense to add the lock around that last one so all > notifier chain calls are handled the same. > >> if (ret) >> return -EINVAL; > > Well, sorry for the dumb question but the fb/fbcon code is pretty hard to follow for me. Why does store_fbstate() and any fb driver's suspsend methods acquire the console lock at all ? Thanks -- Francis -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
