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 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 79350C83F33 for ; Tue, 5 Sep 2023 14:30:07 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 35AC910E542; Tue, 5 Sep 2023 14:30:07 +0000 (UTC) Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 07AD610E541; Tue, 5 Sep 2023 14:30:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1693924205; x=1725460205; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=Z+BiVkXI2KSHQq5poTdeoEuU+DEH+Sr3NnpKHGTTo24=; b=acapXMQdmmQnM4RvvzHHTAeVoFcPafdN4DFKa/ZzGznKoOl2Wq+V0xq2 S6wuZbLWe/mcOYaKf2gWWmUvI6EPsE47CtWa51ioqN7vpqsNKVcmBdyHT duSL4F8RgseeiNWyf2dkc11P2bPbMDD6+DEYdyvt63fdXmYNw+VEbwy97 U+/7+fghmflHDmAiKQGUjiEKXP0oJ0XWazGAE0uk6SAMByJ1BZpybGes/ 1HDyLt0gaPt37jFyzOoM87GxadAIKx8/zBYcNCPHZorcN8r+MEV8qPqGX 4wMwZUZd9WrnPP+KSXBzoWC8y8DhzIFt5RaY9RaR75xLB/SUlQrYX3zNr Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10824"; a="440778586" X-IronPort-AV: E=Sophos;i="6.02,229,1688454000"; d="scan'208";a="440778586" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Sep 2023 07:30:04 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10824"; a="884320656" X-IronPort-AV: E=Sophos;i="6.02,229,1688454000"; d="scan'208";a="884320656" Received: from chenxi4-mobl1.ccr.corp.intel.com (HELO [10.249.254.154]) ([10.249.254.154]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Sep 2023 07:29:54 -0700 Message-ID: <2457e9ba-ecdb-b427-692b-a5c85f9e8828@linux.intel.com> Date: Tue, 5 Sep 2023 16:29:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Content-Language: en-US To: =?UTF-8?Q?Christian_K=c3=b6nig?= , intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org References: <20230905085832.2103-1-thomas.hellstrom@linux.intel.com> <20230905085832.2103-4-thomas.hellstrom@linux.intel.com> From: =?UTF-8?Q?Thomas_Hellstr=c3=b6m?= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Subject: Re: [Intel-xe] [PATCH 3/3] drm/drm_exec: Work around a WW mutex lockdep oddity X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Boris Brezillon , Danilo Krummrich Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" Hi, Christian On 9/5/23 15:14, Christian König wrote: > Am 05.09.23 um 10:58 schrieb Thomas Hellström: >> If *any* object of a certain WW mutex class is locked, lockdep will >> consider *all* mutexes of that class as locked. Also the lock allocation >> tracking code will apparently register only the address of the first >> mutex locked in a sequence. >> This has the odd consequence that if that first mutex is unlocked and >> its memory then freed, the lock alloc tracking code will assume that >> memory >> is freed with a held lock in there. >> >> For now, work around that for drm_exec by releasing the first grabbed >> object lock last. >> >> Related lock alloc tracking warning: >> [  322.660067] ========================= >> [  322.660070] WARNING: held lock freed! >> [  322.660074] 6.5.0-rc7+ #155 Tainted: G     U           N >> [  322.660078] ------------------------- >> [  322.660081] kunit_try_catch/4981 is freeing memory >> ffff888112adc000-ffff888112adc3ff, with a lock still held there! >> [  322.660089] ffff888112adc1a0 >> (reservation_ww_class_mutex){+.+.}-{3:3}, at: >> drm_exec_lock_obj+0x11a/0x600 [drm_exec] >> [  322.660104] 2 locks held by kunit_try_catch/4981: >> [  322.660108]  #0: ffffc9000343fe18 >> (reservation_ww_class_acquire){+.+.}-{0:0}, at: >> test_early_put+0x22f/0x490 [drm_exec_test] >> [  322.660123]  #1: ffff888112adc1a0 >> (reservation_ww_class_mutex){+.+.}-{3:3}, at: >> drm_exec_lock_obj+0x11a/0x600 [drm_exec] >> [  322.660135] >>                 stack backtrace: >> [  322.660139] CPU: 7 PID: 4981 Comm: kunit_try_catch Tainted: G     >> U           N 6.5.0-rc7+ #155 >> [  322.660146] Hardware name: ASUS System Product Name/PRIME B560M-A >> AC, BIOS 0403 01/26/2021 >> [  322.660152] Call Trace: >> [  322.660155]  >> [  322.660158]  dump_stack_lvl+0x57/0x90 >> [  322.660164]  debug_check_no_locks_freed+0x20b/0x2b0 >> [  322.660172]  slab_free_freelist_hook+0xa1/0x160 >> [  322.660179]  ? drm_exec_unlock_all+0x168/0x2a0 [drm_exec] >> [  322.660186]  __kmem_cache_free+0xb2/0x290 >> [  322.660192]  drm_exec_unlock_all+0x168/0x2a0 [drm_exec] >> [  322.660200]  drm_exec_fini+0xf/0x1c0 [drm_exec] >> [  322.660206]  test_early_put+0x289/0x490 [drm_exec_test] >> [  322.660215]  ? __pfx_test_early_put+0x10/0x10 [drm_exec_test] >> [  322.660222]  ? __kasan_check_byte+0xf/0x40 >> [  322.660227]  ? __ksize+0x63/0x140 >> [  322.660233]  ? drmm_add_final_kfree+0x3e/0xa0 [drm] >> [  322.660289]  ? _raw_spin_unlock_irqrestore+0x30/0x60 >> [  322.660294]  ? lockdep_hardirqs_on+0x7d/0x100 >> [  322.660301]  ? __pfx_kunit_try_run_case+0x10/0x10 [kunit] >> [  322.660310]  ? __pfx_kunit_generic_run_threadfn_adapter+0x10/0x10 >> [kunit] >> [  322.660319]  kunit_generic_run_threadfn_adapter+0x4a/0x90 [kunit] >> [  322.660328]  kthread+0x2e7/0x3c0 >> [  322.660334]  ? __pfx_kthread+0x10/0x10 >> [  322.660339]  ret_from_fork+0x2d/0x70 >> [  322.660345]  ? __pfx_kthread+0x10/0x10 >> [  322.660349]  ret_from_fork_asm+0x1b/0x30 >> [  322.660358]  >> [  322.660818]     ok 8 test_early_put >> >> Cc: Christian König >> Cc: Boris Brezillon >> Cc: Danilo Krummrich >> Cc: dri-devel@lists.freedesktop.org >> Signed-off-by: Thomas Hellström >> --- >>   drivers/gpu/drm/drm_exec.c |  2 +- >>   include/drm/drm_exec.h     | 35 +++++++++++++++++++++++++++++++---- >>   2 files changed, 32 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/gpu/drm/drm_exec.c b/drivers/gpu/drm/drm_exec.c >> index ff69cf0fb42a..5d2809de4517 100644 >> --- a/drivers/gpu/drm/drm_exec.c >> +++ b/drivers/gpu/drm/drm_exec.c >> @@ -56,7 +56,7 @@ static void drm_exec_unlock_all(struct drm_exec *exec) >>       struct drm_gem_object *obj; >>       unsigned long index; >>   -    drm_exec_for_each_locked_object(exec, index, obj) { >> +    drm_exec_for_each_locked_object_reverse(exec, index, obj) { > > Well that's a really good catch, just one more additional thought below. > >>           dma_resv_unlock(obj->resv); >>           drm_gem_object_put(obj); >>       } >> diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h >> index e0462361adf9..55764cf7c374 100644 >> --- a/include/drm/drm_exec.h >> +++ b/include/drm/drm_exec.h >> @@ -51,6 +51,20 @@ struct drm_exec { >>       struct drm_gem_object *prelocked; >>   }; >>   +/** >> + * drm_exec_obj() - Return the object for a give drm_exec index >> + * @exec: Pointer to the drm_exec context >> + * @index: The index. >> + * >> + * Return: Pointer to the locked object corresponding to @index if >> + * index is within the number of locked objects. NULL otherwise. >> + */ >> +static inline struct drm_gem_object * >> +drm_exec_obj(struct drm_exec *exec, unsigned long index) >> +{ >> +    return index < exec->num_objects ? exec->objects[index] : NULL; >> +} >> + >>   /** >>    * drm_exec_for_each_locked_object - iterate over all the locked >> objects >>    * @exec: drm_exec object >> @@ -59,10 +73,23 @@ struct drm_exec { >>    * >>    * Iterate over all the locked GEM objects inside the drm_exec object. >>    */ >> -#define drm_exec_for_each_locked_object(exec, index, obj)    \ >> -    for (index = 0, obj = (exec)->objects[0];        \ >> -         index < (exec)->num_objects;            \ >> -         ++index, obj = (exec)->objects[index]) >> +#define drm_exec_for_each_locked_object(exec, index, obj)        \ >> +    for ((index) = 0; ((obj) = drm_exec_obj(exec, index)); ++(index)) > > Mhm, that makes it possible to modify the number of objects while > inside the loop, doesn't it? Sorry, you lost me a bit there. Isn't that possible with the previous code as well? /Thanks, Thomas > > I'm not sure if that's a good idea or not. > > Regards, > Christian. > >> + >> +/** >> + * drm_exec_for_each_locked_object_reverse - iterate over all the >> locked >> + * objects in reverse locking order >> + * @exec: drm_exec object >> + * @index: unsigned long index for the iteration >> + * @obj: the current GEM object >> + * >> + * Iterate over all the locked GEM objects inside the drm_exec >> object in >> + * reverse locking order. Note that @index may go below zero and wrap, >> + * but that will be caught by drm_exec_object(), returning a NULL >> object. >> + */ >> +#define drm_exec_for_each_locked_object_reverse(exec, index, obj)    \ >> +    for ((index) = (exec)->num_objects - 1;                \ >> +         ((obj) = drm_exec_obj(exec, index)); --(index)) >>     /** >>    * drm_exec_until_all_locked - loop until all GEM objects are locked >