Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757548Ab3JQQ0C (ORCPT ); Thu, 17 Oct 2013 12:26:02 -0400 Received: from relay5-d.mail.gandi.net ([217.70.183.197]:49541 "EHLO relay5-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756377Ab3JQQ0A (ORCPT ); Thu, 17 Oct 2013 12:26:00 -0400 X-Originating-IP: 173.246.103.110 Date: Thu, 17 Oct 2013 09:25:52 -0700 From: Josh Triplett To: Larry Finger Cc: Christopher Li , Linux-Sparse , LKML Subject: Re: sparse: possible false report of context imbalance Message-ID: <20131017162551.GA4123@jtriplet-mobl1> References: <525F584C.5010106@lwfinger.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <525F584C.5010106@lwfinger.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1649 Lines: 48 On Wed, Oct 16, 2013 at 10:23:56PM -0500, Larry Finger wrote: > Sparse reports the following: > > CHECK drivers/staging/rtl8188eu/core/rtw_mlme.c > drivers/staging/rtl8188eu/core/rtw_mlme.c:1003:9: warning: context > imbalance in 'rtw_free_assoc_resources' - different lock contexts > for basic block > > The code in question is as follows: > > if (lock_scanned_queue) > spin_lock_bh(&(pmlmepriv->scanned_queue.lock)); > > pwlan = rtw_find_network(&pmlmepriv->scanned_queue, > tgt_network->network.MacAddress); > > if (lock_scanned_queue) > spin_unlock_bh(&(pmlmepriv->scanned_queue.lock)); > > As this fragment uses the identical test to unlock that is used to > lock, and the test variable is not touched, I think this is a false > indication. I am using version 0.4.4 of sparse. Sparse can't track conditional contexts like this; sparse intentionally complains here that you're running the same basic block (the rtw_find_network call) with and without a lock held. The following workaround works when this is legitimate, though it isn't ideal: if (condition) { lock do_thing unlock } else { do_thing } Ideally, Sparse should be able to track conditional contexts, but that would require some form of abstract evaluation, or as a simplistic hack, looking for identical side-effect-free conditional expressions. - Josh Triplett -- 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/