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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1DABEC433EF for ; Wed, 13 Oct 2021 15:37:09 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id AB29E61154 for ; Wed, 13 Oct 2021 15:37:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org AB29E61154 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 149986E9FA; Wed, 13 Oct 2021 15:37:08 +0000 (UTC) Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by gabe.freedesktop.org (Postfix) with ESMTPS id 238836E875; Wed, 13 Oct 2021 15:37:07 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10136"; a="227353283" X-IronPort-AV: E=Sophos;i="5.85,371,1624345200"; d="scan'208";a="227353283" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Oct 2021 08:37:06 -0700 X-IronPort-AV: E=Sophos;i="5.85,371,1624345200"; d="scan'208";a="480852200" Received: from lvoronov-mobl.ger.corp.intel.com (HELO [10.213.252.151]) ([10.213.252.151]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Oct 2021 08:37:05 -0700 Subject: Re: [Intel-gfx] [PATCH] drm/i915: Use dma_resv_iter for waiting in i915_gem_object_wait_reservation. To: Daniel Vetter , Maarten Lankhorst Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org References: <20211013111817.1886880-1-maarten.lankhorst@linux.intel.com> <20211013123203.1953276-1-maarten.lankhorst@linux.intel.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: Date: Wed, 13 Oct 2021 16:37:03 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 13/10/2021 15:00, Daniel Vetter wrote: > On Wed, Oct 13, 2021 at 02:32:03PM +0200, Maarten Lankhorst wrote: >> No memory should be allocated when calling i915_gem_object_wait, >> because it may be called to idle a BO when evicting memory. >> >> Fix this by using dma_resv_iter helpers to call >> i915_gem_object_wait_fence() on each fence, which cleans up the code a lot. >> Also remove dma_resv_prune, it's questionably. >> >> This will result in the following lockdep splat. >> >> <4> [83.538517] ====================================================== >> <4> [83.538520] WARNING: possible circular locking dependency detected >> <4> [83.538522] 5.15.0-rc5-CI-Trybot_8062+ #1 Not tainted >> <4> [83.538525] ------------------------------------------------------ >> <4> [83.538527] gem_render_line/5242 is trying to acquire lock: >> <4> [83.538530] ffffffff8275b1e0 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_track_caller+0x56/0x270 >> <4> [83.538538] >> but task is already holding lock: >> <4> [83.538540] ffff88813471d1e0 (&vm->mutex/1){+.+.}-{3:3}, at: i915_vma_pin_ww+0x1c7/0x970 [i915] >> <4> [83.538638] >> which lock already depends on the new lock. >> <4> [83.538642] >> the existing dependency chain (in reverse order) is: >> <4> [83.538645] >> -> #1 (&vm->mutex/1){+.+.}-{3:3}: >> <4> [83.538649] lock_acquire+0xd3/0x310 >> <4> [83.538654] i915_gem_shrinker_taints_mutex+0x2d/0x50 [i915] >> <4> [83.538730] i915_address_space_init+0xf5/0x1b0 [i915] >> <4> [83.538794] ppgtt_init+0x55/0x70 [i915] >> <4> [83.538856] gen8_ppgtt_create+0x44/0x5d0 [i915] >> <4> [83.538912] i915_ppgtt_create+0x28/0xf0 [i915] >> <4> [83.538971] intel_gt_init+0x130/0x3b0 [i915] >> <4> [83.539029] i915_gem_init+0x14b/0x220 [i915] >> <4> [83.539100] i915_driver_probe+0x97e/0xdd0 [i915] >> <4> [83.539149] i915_pci_probe+0x43/0x1d0 [i915] >> <4> [83.539197] pci_device_probe+0x9b/0x110 >> <4> [83.539201] really_probe+0x1b0/0x3b0 >> <4> [83.539205] __driver_probe_device+0xf6/0x170 >> <4> [83.539208] driver_probe_device+0x1a/0x90 >> <4> [83.539210] __driver_attach+0x93/0x160 >> <4> [83.539213] bus_for_each_dev+0x72/0xc0 >> <4> [83.539216] bus_add_driver+0x14b/0x1f0 >> <4> [83.539220] driver_register+0x66/0xb0 >> <4> [83.539222] hdmi_get_spk_alloc+0x1f/0x50 [snd_hda_codec_hdmi] >> <4> [83.539227] do_one_initcall+0x53/0x2e0 >> <4> [83.539230] do_init_module+0x55/0x200 >> <4> [83.539234] load_module+0x2700/0x2980 >> <4> [83.539237] __do_sys_finit_module+0xaa/0x110 >> <4> [83.539241] do_syscall_64+0x37/0xb0 >> <4> [83.539244] entry_SYSCALL_64_after_hwframe+0x44/0xae >> <4> [83.539247] >> -> #0 (fs_reclaim){+.+.}-{0:0}: >> <4> [83.539251] validate_chain+0xb37/0x1e70 >> <4> [83.539254] __lock_acquire+0x5a1/0xb70 >> <4> [83.539258] lock_acquire+0xd3/0x310 >> <4> [83.539260] fs_reclaim_acquire+0x9d/0xd0 >> <4> [83.539264] __kmalloc_track_caller+0x56/0x270 >> <4> [83.539267] krealloc+0x48/0xa0 >> <4> [83.539270] dma_resv_get_fences+0x1c3/0x280 >> <4> [83.539274] i915_gem_object_wait+0x1ff/0x410 [i915] >> <4> [83.539342] i915_gem_evict_for_node+0x16b/0x440 [i915] >> <4> [83.539412] i915_gem_gtt_reserve+0xff/0x130 [i915] >> <4> [83.539482] i915_vma_pin_ww+0x765/0x970 [i915] >> <4> [83.539556] eb_validate_vmas+0x6fe/0x8e0 [i915] >> <4> [83.539626] i915_gem_do_execbuffer+0x9a6/0x20a0 [i915] >> <4> [83.539693] i915_gem_execbuffer2_ioctl+0x11f/0x2c0 [i915] >> <4> [83.539759] drm_ioctl_kernel+0xac/0x140 >> <4> [83.539763] drm_ioctl+0x201/0x3d0 >> <4> [83.539766] __x64_sys_ioctl+0x6a/0xa0 >> <4> [83.539769] do_syscall_64+0x37/0xb0 >> <4> [83.539772] entry_SYSCALL_64_after_hwframe+0x44/0xae >> <4> [83.539775] >> other info that might help us debug this: >> <4> [83.539778] Possible unsafe locking scenario: >> <4> [83.539781] CPU0 CPU1 >> <4> [83.539783] ---- ---- >> <4> [83.539785] lock(&vm->mutex/1); >> <4> [83.539788] lock(fs_reclaim); >> <4> [83.539791] lock(&vm->mutex/1); >> <4> [83.539794] lock(fs_reclaim); >> <4> [83.539796] >> *** DEADLOCK *** >> <4> [83.539799] 3 locks held by gem_render_line/5242: >> <4> [83.539802] #0: ffffc90000d4bbf0 (reservation_ww_class_acquire){+.+.}-{0:0}, at: i915_gem_do_execbuffer+0x8e5/0x20a0 [i915] >> <4> [83.539870] #1: ffff88811e48bae8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: eb_validate_vmas+0x81/0x8e0 [i915] >> <4> [83.539936] #2: ffff88813471d1e0 (&vm->mutex/1){+.+.}-{3:3}, at: i915_vma_pin_ww+0x1c7/0x970 [i915] >> <4> [83.540011] >> stack backtrace: >> <4> [83.540014] CPU: 2 PID: 5242 Comm: gem_render_line Not tainted 5.15.0-rc5-CI-Trybot_8062+ #1 >> <4> [83.540019] Hardware name: Intel(R) Client Systems NUC11TNHi3/NUC11TNBi3, BIOS TNTGL357.0038.2020.1124.1648 11/24/2020 >> <4> [83.540023] Call Trace: >> <4> [83.540026] dump_stack_lvl+0x56/0x7b >> <4> [83.540030] check_noncircular+0x12e/0x150 >> <4> [83.540034] ? _raw_spin_unlock_irqrestore+0x50/0x60 >> <4> [83.540038] validate_chain+0xb37/0x1e70 >> <4> [83.540042] __lock_acquire+0x5a1/0xb70 >> <4> [83.540046] lock_acquire+0xd3/0x310 >> <4> [83.540049] ? __kmalloc_track_caller+0x56/0x270 >> <4> [83.540052] ? find_held_lock+0x2d/0x90 >> <4> [83.540055] ? dma_resv_get_fences+0x1c3/0x280 >> <4> [83.540058] fs_reclaim_acquire+0x9d/0xd0 >> <4> [83.540061] ? __kmalloc_track_caller+0x56/0x270 >> <4> [83.540064] __kmalloc_track_caller+0x56/0x270 >> <4> [83.540067] krealloc+0x48/0xa0 >> <4> [83.540070] dma_resv_get_fences+0x1c3/0x280 >> <4> [83.540074] i915_gem_object_wait+0x1ff/0x410 [i915] >> <4> [83.540143] i915_gem_evict_for_node+0x16b/0x440 [i915] >> <4> [83.540212] i915_gem_gtt_reserve+0xff/0x130 [i915] >> <4> [83.540281] i915_vma_pin_ww+0x765/0x970 [i915] >> <4> [83.540354] eb_validate_vmas+0x6fe/0x8e0 [i915] >> <4> [83.540420] i915_gem_do_execbuffer+0x9a6/0x20a0 [i915] >> <4> [83.540485] ? lockdep_hardirqs_on+0xbf/0x130 >> <4> [83.540490] ? __lock_acquire+0x5c0/0xb70 >> <4> [83.540495] i915_gem_execbuffer2_ioctl+0x11f/0x2c0 [i915] >> <4> [83.540559] ? i915_gem_do_execbuffer+0x20a0/0x20a0 [i915] >> <4> [83.540622] drm_ioctl_kernel+0xac/0x140 >> <4> [83.540625] drm_ioctl+0x201/0x3d0 >> <4> [83.540628] ? i915_gem_do_execbuffer+0x20a0/0x20a0 [i915] >> <4> [83.540691] __x64_sys_ioctl+0x6a/0xa0 >> <4> [83.540694] do_syscall_64+0x37/0xb0 >> <4> [83.540697] entry_SYSCALL_64_after_hwframe+0x44/0xae >> <4> [83.540700] RIP: 0033:0x7fc314edc50b >> Signed-off-by: Maarten Lankhorst > > Yay for ditching i915/dma_resv_utils.c while we're at it! > > Reviewed-by: Daniel Vetter When Christian sent this patch I've raised one possibly important difference difference (from msg id e0954bdd-2183-f662-8192-c44f931c602b@linux.intel.com): """ Converting this one could be problematic. It's the wait ioctl which used to grab an atomic snapshot and wait for that rendering to complete. With this change I think it has the potential to run forever keeps catching new activity against the same object. I am not sure whether or not the difference is relevant for how userspace uses it but I think needs discussion. Hm actually there are internal callers as well, and at least some of those have the object locked. Would a wider refactoring to separate those into buckets (locked vs unlocked) make sense? """ I don't have sufficient knowledge on how userspace might be using gem_wait to call whether it is a problem or not, or how big. Thoughts? Regards, Tvrtko > >> --- >> drivers/gpu/drm/i915/Makefile | 1 - >> drivers/gpu/drm/i915/dma_resv_utils.c | 17 ------ >> drivers/gpu/drm/i915/dma_resv_utils.h | 13 ----- >> drivers/gpu/drm/i915/gem/i915_gem_shrinker.c | 1 - >> drivers/gpu/drm/i915/gem/i915_gem_wait.c | 56 +++----------------- >> 5 files changed, 8 insertions(+), 80 deletions(-) >> delete mode 100644 drivers/gpu/drm/i915/dma_resv_utils.c >> delete mode 100644 drivers/gpu/drm/i915/dma_resv_utils.h >> >> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile >> index 21b05ed0e4e8..88bb326d9031 100644 >> --- a/drivers/gpu/drm/i915/Makefile >> +++ b/drivers/gpu/drm/i915/Makefile >> @@ -58,7 +58,6 @@ i915-y += i915_drv.o \ >> >> # core library code >> i915-y += \ >> - dma_resv_utils.o \ >> i915_memcpy.o \ >> i915_mm.o \ >> i915_sw_fence.o \ >> diff --git a/drivers/gpu/drm/i915/dma_resv_utils.c b/drivers/gpu/drm/i915/dma_resv_utils.c >> deleted file mode 100644 >> index 7df91b7e4ca8..000000000000 >> --- a/drivers/gpu/drm/i915/dma_resv_utils.c >> +++ /dev/null >> @@ -1,17 +0,0 @@ >> -// SPDX-License-Identifier: MIT >> -/* >> - * Copyright © 2020 Intel Corporation >> - */ >> - >> -#include >> - >> -#include "dma_resv_utils.h" >> - >> -void dma_resv_prune(struct dma_resv *resv) >> -{ >> - if (dma_resv_trylock(resv)) { >> - if (dma_resv_test_signaled(resv, true)) >> - dma_resv_add_excl_fence(resv, NULL); >> - dma_resv_unlock(resv); >> - } >> -} >> diff --git a/drivers/gpu/drm/i915/dma_resv_utils.h b/drivers/gpu/drm/i915/dma_resv_utils.h >> deleted file mode 100644 >> index b9d8fb5f8367..000000000000 >> --- a/drivers/gpu/drm/i915/dma_resv_utils.h >> +++ /dev/null >> @@ -1,13 +0,0 @@ >> -/* SPDX-License-Identifier: MIT */ >> -/* >> - * Copyright © 2020 Intel Corporation >> - */ >> - >> -#ifndef DMA_RESV_UTILS_H >> -#define DMA_RESV_UTILS_H >> - >> -struct dma_resv; >> - >> -void dma_resv_prune(struct dma_resv *resv); >> - >> -#endif /* DMA_RESV_UTILS_H */ >> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c >> index c80e6c1d2bcb..5375f3f9f016 100644 >> --- a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c >> +++ b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c >> @@ -15,7 +15,6 @@ >> >> #include "gt/intel_gt_requests.h" >> >> -#include "dma_resv_utils.h" >> #include "i915_trace.h" >> >> static bool swap_available(void) >> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_wait.c b/drivers/gpu/drm/i915/gem/i915_gem_wait.c >> index f909aaa09d9c..e59304a76b2c 100644 >> --- a/drivers/gpu/drm/i915/gem/i915_gem_wait.c >> +++ b/drivers/gpu/drm/i915/gem/i915_gem_wait.c >> @@ -10,7 +10,6 @@ >> >> #include "gt/intel_engine.h" >> >> -#include "dma_resv_utils.h" >> #include "i915_gem_ioctls.h" >> #include "i915_gem_object.h" >> >> @@ -37,56 +36,17 @@ i915_gem_object_wait_reservation(struct dma_resv *resv, >> unsigned int flags, >> long timeout) >> { >> - struct dma_fence *excl; >> - bool prune_fences = false; >> - >> - if (flags & I915_WAIT_ALL) { >> - struct dma_fence **shared; >> - unsigned int count, i; >> - int ret; >> + struct dma_resv_iter cursor; >> + struct dma_fence *fence; >> >> - ret = dma_resv_get_fences(resv, &excl, &count, &shared); >> - if (ret) >> - return ret; >> - >> - for (i = 0; i < count; i++) { >> - timeout = i915_gem_object_wait_fence(shared[i], >> - flags, timeout); >> - if (timeout < 0) >> - break; >> + dma_resv_iter_begin(&cursor, resv, flags & I915_WAIT_ALL); >> + dma_resv_for_each_fence_unlocked(&cursor, fence) { >> >> - dma_fence_put(shared[i]); >> - } >> - >> - for (; i < count; i++) >> - dma_fence_put(shared[i]); >> - kfree(shared); >> - >> - /* >> - * If both shared fences and an exclusive fence exist, >> - * then by construction the shared fences must be later >> - * than the exclusive fence. If we successfully wait for >> - * all the shared fences, we know that the exclusive fence >> - * must all be signaled. If all the shared fences are >> - * signaled, we can prune the array and recover the >> - * floating references on the fences/requests. >> - */ >> - prune_fences = count && timeout >= 0; >> - } else { >> - excl = dma_resv_get_excl_unlocked(resv); >> + timeout = i915_gem_object_wait_fence(fence, flags, timeout); >> + if (timeout <= 0) >> + break; >> } >> - >> - if (excl && timeout >= 0) >> - timeout = i915_gem_object_wait_fence(excl, flags, timeout); >> - >> - dma_fence_put(excl); >> - >> - /* >> - * Opportunistically prune the fences iff we know they have *all* been >> - * signaled. >> - */ >> - if (prune_fences) >> - dma_resv_prune(resv); >> + dma_resv_iter_end(&cursor); >> >> return timeout; >> } >> -- >> 2.33.0 >> >