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([2a02:908:1252:fb60:4276:c469:b15d:9dea]) by smtp.gmail.com with ESMTPSA id u4-20020a170906780400b006ce69ff6050sm5729145ejm.69.2022.03.28.03.28.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 28 Mar 2022 03:28:32 -0700 (PDT) Message-ID: <338d0623-1161-c958-101f-dc7d8ef12f99@gmail.com> Date: Mon, 28 Mar 2022 12:28:31 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH 1/2] dma-buf: add dma_fence_unwrap Content-Language: en-US To: =?UTF-8?Q?Christian_K=c3=b6nig?= , =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= , Daniel Vetter Cc: sumit.semwal@linaro.org, gustavo@padovan.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, Dave Airlie References: <20220311110244.1245-1-christian.koenig@amd.com> <35cc3bd5-c0ab-0bd1-9603-4971234fbcd6@amd.com> From: =?UTF-8?Q?Christian_K=c3=b6nig?= In-Reply-To: <35cc3bd5-c0ab-0bd1-9603-4971234fbcd6@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Hi Ville & Daniel, Am 25.03.22 um 16:28 schrieb Christian König: > Am 25.03.22 um 16:25 schrieb Ville Syrjälä: >> On Fri, Mar 11, 2022 at 12:02:43PM +0100, Christian König wrote: >>> Add a general purpose helper to deep dive into >>> dma_fence_chain/dma_fence_array >>> structures and iterate over all the fences in them. >>> >>> This is useful when we need to flatten out all fences in those >>> structures. >>> >>> Signed-off-by: Christian König >> One of the dma-buf patches took down Intel CI. Looks like every >> machine oopses in some sync_file thing now: >> <1>[  260.470008] BUG: kernel NULL pointer dereference, address: >> 0000000000000010 >> <1>[  260.470020] #PF: supervisor read access in kernel mode >> <1>[  260.470025] #PF: error_code(0x0000) - not-present page >> <6>[  260.470030] PGD 0 P4D 0 >> <4>[  260.470035] Oops: 0000 [#1] PREEMPT SMP NOPTI >> <4>[  260.470040] CPU: 0 PID: 5306 Comm: core_hotunplug Not tainted >> 5.17.0-CI-CI_DRM_11405+ #1 >> <4>[  260.470049] Hardware name: Intel Corporation Jasper Lake Client >> Platform/Jasperlake DDR4 SODIMM RVP, BIOS >> JSLSFWI1.R00.2385.D02.2010160831 10/16/2020 >> <4>[  260.470058] RIP: 0010:dma_fence_array_first+0x19/0x20 I've looked into this and the root cause seems to be that the new code doesn't handle dma_fence_arrays with zero elements. That is rather easy to fix, but a dma_fence_array with zero number of elements is most likely a bug because under the wrong circumstances it can create a dma_fence instance which will never signal. I've send out a patch on Frinday ([PATCH] dma-buf: WIP dma_fence_array_first fix) which avoids the crash and prints a warning if anybody tries to create a dma_fence_array with zero length. Can you test this? Thanks in advance, Christian.