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=-7.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 42E64C433EF for ; Thu, 9 Sep 2021 05:38:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2340E61167 for ; Thu, 9 Sep 2021 05:38:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350816AbhIIFjV (ORCPT ); Thu, 9 Sep 2021 01:39:21 -0400 Received: from mga05.intel.com ([192.55.52.43]:53754 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348026AbhIIFjT (ORCPT ); Thu, 9 Sep 2021 01:39:19 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10101"; a="306250160" X-IronPort-AV: E=Sophos;i="5.85,279,1624345200"; d="scan'208";a="306250160" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Sep 2021 22:38:10 -0700 X-IronPort-AV: E=Sophos;i="5.85,279,1624345200"; d="scan'208";a="548340145" Received: from shishpan-mobl2.ccr.corp.intel.com (HELO [10.252.43.251]) ([10.252.43.251]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Sep 2021 22:38:08 -0700 Subject: Re: [PATCH] kernel/locking: Add context to ww_mutex_trylock. To: Peter Zijlstra 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 References: <20210907132044.157225-1-maarten.lankhorst@linux.intel.com> From: Maarten Lankhorst Message-ID: <96ab9cf1-250a-8f34-51ec-4a7f66a87b39@linux.intel.com> Date: Thu, 9 Sep 2021 07:38:06 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Op 08-09-2021 om 12:14 schreef Peter Zijlstra: > 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 What tree has that file?