Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933967Ab3EFX4U (ORCPT ); Mon, 6 May 2013 19:56:20 -0400 Received: from mail-ve0-f202.google.com ([209.85.128.202]:48754 "EHLO mail-ve0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932305Ab3EFXu0 (ORCPT ); Mon, 6 May 2013 19:50:26 -0400 From: Colin Cross To: linux-kernel@vger.kernel.org Cc: Pavel Machek , "Rafael J. Wysocki" , Peter Zijlstra , Ingo Molnar , Andrew Morton , Mandeep Singh Baines , Colin Cross , Oleg Nesterov , linux-nfs@vger.kernel.org, linux-pm@vger.kernel.org, netdev@vger.kernel.org, Linus Torvalds , Tejun Heo , Len Brown Subject: [PATCH v3 02/16] freezer: add unsafe versions of freezable helpers for CIFS Date: Mon, 6 May 2013 16:50:07 -0700 Message-Id: <1367884221-20462-3-git-send-email-ccross@android.com> X-Mailer: git-send-email 1.8.2.1 In-Reply-To: <1367884221-20462-1-git-send-email-ccross@android.com> References: <1367884221-20462-1-git-send-email-ccross@android.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2368 Lines: 62 CIFS calls wait_event_freezekillable_unsafe with a VFS lock held, which is unsafe and will cause lockdep warnings when 6aa9707 "lockdep: check that no locks held at freeze time" is reapplied (it was reverted in dbf520a). CIFS shouldn't be doing this, but it has long-running syscalls that must hold a lock but also shouldn't block suspend. Until CIFS freeze handling is rewritten to use a signal to exit out of the critical section, add a new wait_event_freezekillable_unsafe helper that will not run the lockdep test when 6aa9707 is reapplied, and call it from CIFS. In practice the likley result of holding the lock while freezing is that a second task blocked on the lock will never freeze, aborting suspend, but it is possible to manufacture a case using the cgroup freezer, the lock, and the suspend freezer to create a deadlock. Silencing the lockdep warning here will allow problems to be found in other drivers that may have a more serious deadlock risk, and prevent new problems from being added. Signed-off-by: Colin Cross --- include/linux/freezer.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/include/linux/freezer.h b/include/linux/freezer.h index 5b31e21c..d3c038e 100644 --- a/include/linux/freezer.h +++ b/include/linux/freezer.h @@ -212,6 +212,16 @@ static inline bool freezer_should_skip(struct task_struct *p) __retval; \ }) +/* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */ +#define wait_event_freezekillable_unsafe(wq, condition) \ +({ \ + int __retval; \ + freezer_do_not_count(); \ + __retval = wait_event_killable(wq, (condition)); \ + freezer_count_unsafe(); \ + __retval; \ +}) + #define wait_event_freezable(wq, condition) \ ({ \ int __retval; \ @@ -277,6 +287,9 @@ static inline void set_freezable(void) {} #define wait_event_freezekillable(wq, condition) \ wait_event_killable(wq, condition) +#define wait_event_freezekillable_unsafe(wq, condition) \ + wait_event_killable(wq, condition) + #endif /* !CONFIG_FREEZER */ #endif /* FREEZER_H_INCLUDED */ -- 1.8.2.1 -- 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/