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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 3891EC433EF for ; Wed, 8 Sep 2021 10:14:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 14C79610E9 for ; Wed, 8 Sep 2021 10:14:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347877AbhIHKPq (ORCPT ); Wed, 8 Sep 2021 06:15:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57868 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231723AbhIHKPp (ORCPT ); Wed, 8 Sep 2021 06:15:45 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F2C9EC061575 for ; Wed, 8 Sep 2021 03:14:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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; bh=0ciSKTQVg9jB/JRJoAkcU2i5AuVKoWJVYLmKxmFW0dM=; b=l7+Z82aBQnq1R3K5PazXQAzEJP IWQoiNUrAooJEXd4P7SHQB1oLoOYQj/Pa+TdliJjR8Peq3rtKnYQxBO8GmQLc53tkcU6/+rM83Ni0 iaiX5mhUZSyRnbmUfA6FdESgxucQ2TbIasegfBGA9OGCvdY/yHAZDBXaKx45XqcCMYMjWkLFr51rX hOqZrx91SyCvnwb3N6si5jbGFBXyChyhywAOaofGZosKzqO+tJNS74AG7sxUhHHydZWZAm29o4xva bRb8h5PZkhFxvubcE9o7N31BPpeidvUEHNz5dXUQeNcCYDvguwX5ndYU8OiQ7E6W99kRgqvuUXex4 JzizeQ7w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mNub3-001cTF-BM; Wed, 08 Sep 2021 10:14:25 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 7FD16300332; Wed, 8 Sep 2021 12:14:23 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 681AF2067E684; Wed, 8 Sep 2021 12:14:23 +0200 (CEST) Date: Wed, 8 Sep 2021 12:14:23 +0200 From: Peter Zijlstra To: Maarten Lankhorst Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Ingo Molnar , Will Deacon , Waiman Long , Boqun Feng , Liam Girdwood , Mark Brown , linux-kernel@vger.kernel.org Subject: Re: [PATCH] kernel/locking: Add context to ww_mutex_trylock. Message-ID: References: <20210907132044.157225-1-maarten.lankhorst@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210907132044.157225-1-maarten.lankhorst@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 07, 2021 at 03:20:44PM +0200, Maarten Lankhorst wrote: > i915 will soon gain an eviction path that trylock a whole lot of locks > for eviction, getting dmesg failures like below: > > BUG: MAX_LOCK_DEPTH too low! > turning off the locking correctness validator. > depth: 48 max: 48! > 48 locks held by i915_selftest/5776: > #0: ffff888101a79240 (&dev->mutex){....}-{3:3}, at: __driver_attach+0x88/0x160 > #1: ffffc900009778c0 (reservation_ww_class_acquire){+.+.}-{0:0}, at: i915_vma_pin.constprop.63+0x39/0x1b0 [i915] > #2: ffff88800cf74de8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_vma_pin.constprop.63+0x5f/0x1b0 [i915] > #3: ffff88810c7f9e38 (&vm->mutex/1){+.+.}-{3:3}, at: i915_vma_pin_ww+0x1c4/0x9d0 [i915] > #4: ffff88810bad5768 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915] > #5: ffff88810bad60e8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915] > ... > #46: ffff88811964d768 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915] > #47: ffff88811964e0e8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915] > INFO: lockdep is turned off. > As an intermediate solution, add an acquire context to ww_mutex_trylock, > which allows us to do proper nesting annotations on the trylocks, making > the above lockdep splat disappear. Fair enough I suppose. > +/** > + * ww_mutex_trylock - tries to acquire the w/w mutex with optional acquire context > + * @lock: mutex to lock > + * @ctx: optional w/w acquire context > + * > + * Trylocks a mutex with the optional acquire context; no deadlock detection is > + * possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise. > + * > + * Unlike ww_mutex_lock, no deadlock handling is performed. However, if a @ctx is > + * specified, -EALREADY and -EDEADLK handling may happen in calls to ww_mutex_lock. > + * > + * A mutex acquired with this function must be released with ww_mutex_unlock. > + */ > +int __sched > +ww_mutex_trylock(struct ww_mutex *ww, struct ww_acquire_ctx *ctx) > +{ > + bool locked; > + > + if (!ctx) > + return mutex_trylock(&ww->base); > + > +#ifdef CONFIG_DEBUG_MUTEXES > + DEBUG_LOCKS_WARN_ON(ww->base.magic != &ww->base); > +#endif > + > + preempt_disable(); > + locked = __mutex_trylock(&ww->base); > + > + if (locked) { > + ww_mutex_set_context_fastpath(ww, ctx); > + mutex_acquire_nest(&ww->base.dep_map, 0, 1, &ctx->dep_map, _RET_IP_); > + } > + preempt_enable(); > + > + return locked; > +} > +EXPORT_SYMBOL(ww_mutex_trylock); You'll need a similar hunk in ww_rt_mutex.c