From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04962C43387 for ; Thu, 10 Jan 2019 15:21:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C2456214C6 for ; Thu, 10 Jan 2019 15:21:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="QFYdbMda" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729577AbfAJPU7 (ORCPT ); Thu, 10 Jan 2019 10:20:59 -0500 Received: from merlin.infradead.org ([205.233.59.134]:47330 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727753AbfAJPU7 (ORCPT ); Thu, 10 Jan 2019 10:20:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=UTi/ZbXdhwyBx9fxlkGH8Kdg1qUu+5Y4mOSxMllo1nM=; b=QFYdbMdag3X/xSPQv0CyG7sos xAMWVdZUKJLcHBC+4r/F0uoZT32bjS62X1OMWBqZXmkhJeijVOqSmktaDW80WyO/fNxJYJ0gzzRur y5Q4DUNyJ2XvIn2OgUOsFwb+UK2ZRA9JnXg91LRZck6s2DyNwBiLGkYaesltp1KQEoKH3CsFOgzUH BlMuPWnWxrlixyUb7fgn8o0w6IUzT/onbmBiL+TRewgU0Grny7zz3R6O0Jf54Wjp/PR+W/lH3nRN0 GiQN92pKZWK0ddmoUUdTjyVFYrFYH+odLNZz/myB39Pt/wlWGf01HMtuA0A54iWM5kNQNrz2of/C5 gge02qscA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1ghc8N-0004xm-Vg; Thu, 10 Jan 2019 15:20:40 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 9982B2040B9FD; Thu, 10 Jan 2019 16:20:35 +0100 (CET) Date: Thu, 10 Jan 2019 16:20:35 +0100 From: Peter Zijlstra To: Bart Van Assche Cc: mingo@redhat.com, tj@kernel.org, longman@redhat.com, johannes.berg@intel.com, linux-kernel@vger.kernel.org, Johannes Berg Subject: Re: [PATCH v5 07/15] locking/lockdep: Free lock classes that are no longer in use Message-ID: <20190110152035.GF30894@hirez.programming.kicks-ass.net> References: <20181217213002.73776-1-bvanassche@acm.org> <20181217213002.73776-8-bvanassche@acm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181217213002.73776-8-bvanassche@acm.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Bart, Sorry for the delay; real-life and holidays got in the way :/ On Mon, Dec 17, 2018 at 01:29:54PM -0800, Bart Van Assche wrote: > +/* Remove a class from a lock chain. Must be called with the graph lock held. */ > +static void remove_class_from_lock_chain(struct lock_chain *chain, > + struct lock_class *class) > +{ > +#ifdef CONFIG_PROVE_LOCKING > + struct lock_chain *new_chain; > + u64 chain_key; > + int i; > + > + for (i = chain->base; i < chain->base + chain->depth; i++) { > + if (chain_hlocks[i] != class - lock_classes) > + continue; > + /* The code below leaks one chain_hlock[] entry. */ > + if (--chain->depth > 0) > + memmove(&chain_hlocks[i], &chain_hlocks[i + 1], > + (chain->base + chain->depth - i) * > + sizeof(chain_hlocks[0])); > + /* > + * Each lock class occurs at most once in a lock chain so once > + * we found a match we can break out of this loop. > + */ > + goto recalc; > + } > + /* Since the chain has not been modified, return. */ > + return; > + > +recalc: > + chain_key = 0; > + for (i = chain->base; i < chain->base + chain->depth; i++) > + chain_key = iterate_chain_key(chain_key, chain_hlocks[i] + 1); > + if (chain->depth && chain->chain_key == chain_key) > + return; > + /* Overwrite the chain key for concurrent RCU readers. */ > + WRITE_ONCE(chain->chain_key, chain_key); > + /* > + * Note: calling hlist_del_rcu() from inside a > + * hlist_for_each_entry_rcu() loop is safe. > + */ > + hlist_del_rcu(&chain->entry); > + if (chain->depth == 0) > + return; > + /* > + * If the modified lock chain matches an existing lock chain, drop > + * the modified lock chain. > + */ > + if (lookup_chain_cache(chain_key)) > + return; > + if (WARN_ON_ONCE(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) { > + debug_locks_off(); > + return; > + } > + /* > + * Leak *chain because it is not safe to reinsert it before an RCU > + * grace period has expired. > + */ > + new_chain = lock_chains + nr_lock_chains++; > + *new_chain = *chain; > + hlist_add_head_rcu(&new_chain->entry, chainhashentry(chain_key)); > +#endif > +} Leaking a chain_hlocks[] and lock_chains[] entry is pretty gross, but yes that should work.