Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933007Ab1EXTxk (ORCPT ); Tue, 24 May 2011 15:53:40 -0400 Received: from mail-ww0-f44.google.com ([74.125.82.44]:55359 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932866Ab1EXTxj (ORCPT ); Tue, 24 May 2011 15:53:39 -0400 From: Fabio Erculiani To: linux-fbdev@vger.kernel.org Cc: lethal@linux-sh.org, linux-kernel@vger.kernel.org, Fabio Erculiani Subject: [PATCH] fbmem: fix race condition between register_framebuffer() and fb_open() Date: Tue, 24 May 2011 21:54:31 +0200 Message-Id: <1306266871-12464-1-git-send-email-lxnay@sabayon.org> X-Mailer: git-send-email 1.7.5.rc1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1618 Lines: 50 register_framebuffer() acquires registration_lock, then calls do_register_framebuffer() which calls fb_notifier_call_chain() which calls fb_open() which calls get_fb_info() which tries (at last) to acquire registration_lock again. This is a workaround. Signed-off-by: Fabio Erculiani --- drivers/video/fbmem.c | 13 ++++++++++++- 1 files changed, 12 insertions(+), 1 deletions(-) diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c index 5aac00e..b9831a0 100644 --- a/drivers/video/fbmem.c +++ b/drivers/video/fbmem.c @@ -1628,6 +1628,11 @@ static int do_register_framebuffer(struct fb_info *fb_info) event.info = fb_info; if (!lock_fb_info(fb_info)) return -ENODEV; + + /* FIXME: unlock registration mutex before registration + * notification is sent, in order to avoid deadlock. + */ + mutex_unlock(®istration_lock); fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event); unlock_fb_info(fb_info); return 0; @@ -1692,7 +1697,13 @@ register_framebuffer(struct fb_info *fb_info) mutex_lock(®istration_lock); ret = do_register_framebuffer(fb_info); - mutex_unlock(®istration_lock); + if (ret != 0) + /* + * FIXME: mutex is unlocked only if ret == 0. + * This is the second part of the workaround + * that prevents deadlocking. + */ + mutex_unlock(®istration_lock); return ret; } -- 1.7.5.rc1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/