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Date:   Fri, 30 Sep 2022 13:26:05 +0200
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Subject: Re: [PATCH] drm/sched: Fix kernel NULL pointer dereference error
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To:     Arvind Yadav <Arvind.Yadav@amd.com>, andrey.grodzovsky@amd.com,
        shashank.sharma@amd.com, amaranath.somalapuram@amd.com,
        Arunpravin.PaneerSelvam@amd.com, sumit.semwal@linaro.org,
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        linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
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        steven.price@arm.com
References: <20220930084810.4639-1-Arvind.Yadav@amd.com>
From:   =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>
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Am 30.09.22 um 10:48 schrieb Arvind Yadav:
> BUG: kernel NULL pointer dereference, address: 0000000000000088
>   #PF: supervisor read access in kernel mode
>   #PF: error_code(0x0000) - not-present page
>   PGD 0 P4D 0
>   Oops: 0000 [#1] PREEMPT SMP NOPTI
>   CPU: 2 PID: 0 Comm: swapper/2 Not tainted 6.0.0-rc2-custom #1
>   Arvind : [dma_fence_default_wait _START] timeout = -1
>   Hardware name: AMD Dibbler/Dibbler, BIOS RDB1107CC 09/26/2018
>   RIP: 0010:drm_sched_job_done.isra.0+0x11/0x140 [gpu_sched]
>   Code: 8b fe ff ff be 03 00 00 00 e8 7b da b7 e3 e9 d4 fe ff ff 66 0f 1f 44 00 00 0f 1f 44 00 00 55 48 89 e5 41 55 41 54 49 89 fc 53 <48> 8b 9f 88 00 00 00 f0 ff 8b f0 00 00 00 48 8b 83 80 01 00 00 f0
>   RSP: 0018:ffffb1b1801d4d38 EFLAGS: 00010087
>   RAX: ffffffffc0aa48b0 RBX: ffffb1b1801d4d70 RCX: 0000000000000018
>   RDX: 000036c70afb7c1d RSI: ffff8a45ca413c60 RDI: 0000000000000000
>   RBP: ffffb1b1801d4d50 R08: 00000000000000b5 R09: 0000000000000000
>   R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
>   R13: ffffb1b1801d4d70 R14: ffff8a45c4160000 R15: ffff8a45c416a708
>   FS:  0000000000000000(0000) GS:ffff8a48a0a80000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 0000000000000088 CR3: 000000014ad50000 CR4: 00000000003506e0
>   Call Trace:
>    <IRQ>
>    drm_sched_job_done_cb+0x12/0x20 [gpu_sched]
>    dma_fence_signal_timestamp_locked+0x7e/0x110
>    dma_fence_signal+0x31/0x60
>    amdgpu_fence_process+0xc4/0x140 [amdgpu]
>    gfx_v9_0_eop_irq+0x9d/0xd0 [amdgpu]
>    amdgpu_irq_dispatch+0xb7/0x210 [amdgpu]
>    amdgpu_ih_process+0x86/0x100 [amdgpu]
>    amdgpu_irq_handler+0x24/0x60 [amdgpu]
>    __handle_irq_event_percpu+0x4b/0x190
>    handle_irq_event_percpu+0x15/0x50
>    handle_irq_event+0x39/0x60
>    handle_edge_irq+0xaf/0x210
>    __common_interrupt+0x6e/0x110
>    common_interrupt+0xc1/0xe0
>    </IRQ>
>    <TASK>

How is this triggered any why haven't we seen it before?

Christian

> Signed-off-by: Arvind Yadav <Arvind.Yadav@amd.com>
> ---
>   drivers/gpu/drm/scheduler/sched_main.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index 6684d88463b4..390272f6b126 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -172,7 +172,12 @@ drm_sched_rq_select_entity(struct drm_sched_rq *rq)
>   static void drm_sched_job_done(struct drm_sched_job *s_job)
>   {
>   	struct drm_sched_fence *s_fence = s_job->s_fence;
> -	struct drm_gpu_scheduler *sched = s_fence->sched;
> +	struct drm_gpu_scheduler *sched;
> +
> +	if (!s_fence)
> +		return;
> +
> +	sched = s_fence->sched;
>   
>   	atomic_dec(&sched->hw_rq_count);
>   	atomic_dec(sched->score);