Date:   Wed, 3 Feb 2021 13:21:20 +0100
From:   Christian König <ckoenig.leichtzumerken@...il.com>
To:     Daniel Gomez <daniel@...c.com>, Daniel Vetter <daniel@...ll.ch>
Cc:     Alex Deucher <alexander.deucher@....com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Christian König <christian.koenig@....com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [amdgpu] deadlock

Am 03.02.21 um 12:45 schrieb Daniel Gomez:
> On Wed, 3 Feb 2021 at 10:47, Daniel Gomez <daniel@...c.com> wrote:
>> On Wed, 3 Feb 2021 at 10:17, Daniel Vetter <daniel@...ll.ch> wrote:
>>> On Wed, Feb 3, 2021 at 9:51 AM Christian König <christian.koenig@....com> wrote:
>>>> Am 03.02.21 um 09:48 schrieb Daniel Vetter:
>>>>> On Wed, Feb 3, 2021 at 9:36 AM Christian König <christian.koenig@....com> wrote:
>>>>>> Hi Daniel,
>>>>>>
>>>>>> this is not a deadlock, but rather a hardware lockup.
>>>>> Are you sure? Ime getting stuck in dma_fence_wait has generally good
>>>>> chance of being a dma_fence deadlock. GPU hang should never result in
>>>>> a forever stuck dma_fence.
>>>> Yes, I'm pretty sure. Otherwise the hardware clocks wouldn't go up like
>>>> this.
>>> Maybe clarifying, could be both. TDR should notice and get us out of
>>> this, but if there's a dma_fence deadlock and we can't re-emit or
>>> force complete the pending things, then we're stuck for good.
>>> -Daniel
>>>
>>>> Question is rather why we end up in the userptr handling for GFX? Our
>>>> ROCm OpenCL stack shouldn't use this.
>>>>
>>>>> Daniel, can you pls re-hang your machine and then dump backtraces of
>>>>> all tasks into dmesg with sysrq-t, and then attach that? Without all
>>>>> the backtraces it's tricky to construct the full dependency chain of
>>>>> what's going on. Also is this plain -rc6, not some more patches on
>>>>> top?
>>>> Yeah, that's still a good idea to have.
>> Here the full backtrace dmesg logs after the hang:
>> https://pastebin.com/raw/kzivm2L3
>>
>> This is another dmesg log with the backtraces after SIGKILL the matrix process:
>> (I didn't have the sysrq enable at the time):
>> https://pastebin.com/raw/pRBwGcj1
> I've now removed all our v4l2 patches and did the same test with the 'plain'
> mainline version (-rc6).
>
> Reference: 3aaf0a27ffc29b19a62314edd684b9bc6346f9a8
>
> Same error, same behaviour. Full dmesg log attached:
> https://pastebin.com/raw/KgaEf7Y1
> Note:
>    dmesg with sysrq-t before running the test starts in [  122.016502]
> sysrq: Show State
>    dmesg with sysrq-t after the test starts in: [  495.587671] sysrq: Show State

There is nothing amdgpu related in there except for waiting for the 
hardware.

This is a pretty standard hardware lockup, but I'm still waiting for an 
explanation why we end up in this call path in the first place.

Christian.

>
>
>>>> Christian.
>>>>
>>>>> -Daniel
>>>>>
>>>>>> Which OpenCl stack are you using?
>>>>>>
>>>>>> Regards,
>>>>>> Christian.
>>>>>>
>>>>>> Am 03.02.21 um 09:33 schrieb Daniel Gomez:
>>>>>>> Hi all,
>>>>>>>
>>>>>>> I have a deadlock with the amdgpu mainline driver when running in parallel two
>>>>>>> OpenCL applications. So far, we've been able to replicate it easily by executing
>>>>>>> clinfo and MatrixMultiplication (from AMD opencl-samples). It's quite old the
>>>>>>> opencl-samples so, if you have any other suggestion for testing I'd be very
>>>>>>> happy to test it as well.
>>>>>>>
>>>>>>> How to replicate the issue:
>>>>>>>
>>>>>>> # while true; do /usr/bin/MatrixMultiplication --device gpu \
>>>>>>>        --deviceId 0 -x 1000 -y 1000 -z 1000 -q -t -i 50; done
>>>>>>> # while true; do clinfo; done
>>>>>>>
>>>>>>> Output:
>>>>>>>
>>>>>>> After a minute or less (sometimes could be more) I can see that
>>>>>>> MatrixMultiplication and clinfo hang. In addition, with radeontop you can see
>>>>>>> how the Graphics pipe goes from ~50% to 100%. Also the shader clocks
>>>>>>> goes up from ~35% to ~96%.
>>>>>>>
>>>>>>> clinfo keeps printing:
>>>>>>> ioctl(7, DRM_IOCTL_SYNCOBJ_WAIT, 0x7ffe46e5f950) = -1 ETIME (Timer expired)
>>>>>>>
>>>>>>> And MatrixMultiplication prints the following (strace) if you try to
>>>>>>> kill the process:
>>>>>>>
>>>>>>> sched_yield()                           = 0
>>>>>>> futex(0x557e945343b8, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 0,
>>>>>>> NULL, FUTEX_BITSET_MATCH_ANYstrace: Process 651 detached
>>>>>>>     <detached ...>
>>>>>>>
>>>>>>> After this, the gpu is not functional at all and you'd need a power cycle reset
>>>>>>> to restore the system.
>>>>>>>
>>>>>>> Hardware info:
>>>>>>> CPU: AMD Ryzen Embedded V1605B with Radeon Vega Gfx (8) @ 2.000GHz
>>>>>>> GPU: AMD ATI Radeon Vega Series / Radeon Vega Mobile Series
>>>>>>>
>>>>>>> 03:00.0 VGA compatible controller: Advanced Micro Devices, Inc.
>>>>>>> [AMD/ATI] Raven Ridge [Radeon Vega Series / Radeon Vega Mobile Series]
>>>>>>> (rev 83)
>>>>>>>        DeviceName: Broadcom 5762
>>>>>>>        Subsystem: Advanced Micro Devices, Inc. [AMD/ATI] Raven Ridge
>>>>>>> [Radeon Vega Series / Radeon Vega Mobile Series]
>>>>>>>        Kernel driver in use: amdgpu
>>>>>>>        Kernel modules: amdgpu
>>>>>>>
>>>>>>> Linux kernel info:
>>>>>>>
>>>>>>> root@...222:~# uname -a
>>>>>>> Linux qt5222 5.11.0-rc6-qtec-standard #2 SMP Tue Feb 2 09:41:46 UTC
>>>>>>> 2021 x86_64 x86_64 x86_64 GNU/Linux
>>>>>>>
>>>>>>> By enabling the kernel locks stats I could see the MatrixMultiplication is
>>>>>>> hanged in the amdgpu_mn_invalidate_gfx function:
>>>>>>>
>>>>>>> [  738.359202] 1 lock held by MatrixMultiplic/653:
>>>>>>> [  738.359206]  #0: ffff88810e364fe0
>>>>>>> (&adev->notifier_lock){+.+.}-{3:3}, at:
>>>>>>> amdgpu_mn_invalidate_gfx+0x34/0xa0 [amdgpu]
>>>>>>>
>>>>>>> I can see in the the amdgpu_mn_invalidate_gfx function: the
>>>>>>> dma_resv_wait_timeout_rcu uses wait_all (fences) and MAX_SCHEDULE_TIMEOUT so, I
>>>>>>> guess the code gets stuck there waiting forever. According to the
>>>>>>> documentation: "When somebody tries to invalidate the page tables we block the
>>>>>>> update until all operations on the pages in question are completed, then those
>>>>>>> pages are marked  as accessed and also dirty if it wasn’t a read only access."
>>>>>>> Looks like the fences are deadlocked and therefore, it never returns. Could it
>>>>>>> be possible? any hint to where can I look to fix this?
>>>>>>>
>>>>>>> Thank you  in advance.
>>>>>>>
>>>>>>> Here the full dmesg output:
>>>>>>>
>>>>>>> [  738.337726] INFO: task MatrixMultiplic:653 blocked for more than 122 seconds.
>>>>>>> [  738.344937]       Not tainted 5.11.0-rc6-qtec-standard #2
>>>>>>> [  738.350384] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
>>>>>>> disables this message.
>>>>>>> [  738.358240] task:MatrixMultiplic state:D stack:    0 pid:  653
>>>>>>> ppid:     1 flags:0x00004000
>>>>>>> [  738.358254] Call Trace:
>>>>>>> [  738.358261]  ? dma_fence_default_wait+0x1eb/0x230
>>>>>>> [  738.358276]  __schedule+0x370/0x960
>>>>>>> [  738.358291]  ? dma_fence_default_wait+0x117/0x230
>>>>>>> [  738.358297]  ? dma_fence_default_wait+0x1eb/0x230
>>>>>>> [  738.358305]  schedule+0x51/0xc0
>>>>>>> [  738.358312]  schedule_timeout+0x275/0x380
>>>>>>> [  738.358324]  ? dma_fence_default_wait+0x1eb/0x230
>>>>>>> [  738.358332]  ? mark_held_locks+0x4f/0x70
>>>>>>> [  738.358341]  ? dma_fence_default_wait+0x117/0x230
>>>>>>> [  738.358347]  ? lockdep_hardirqs_on_prepare+0xd4/0x180
>>>>>>> [  738.358353]  ? _raw_spin_unlock_irqrestore+0x39/0x40
>>>>>>> [  738.358362]  ? dma_fence_default_wait+0x117/0x230
>>>>>>> [  738.358370]  ? dma_fence_default_wait+0x1eb/0x230
>>>>>>> [  738.358375]  dma_fence_default_wait+0x214/0x230
>>>>>>> [  738.358384]  ? dma_fence_release+0x1a0/0x1a0
>>>>>>> [  738.358396]  dma_fence_wait_timeout+0x105/0x200
>>>>>>> [  738.358405]  dma_resv_wait_timeout_rcu+0x1aa/0x5e0
>>>>>>> [  738.358421]  amdgpu_mn_invalidate_gfx+0x55/0xa0 [amdgpu]
>>>>>>> [  738.358688]  __mmu_notifier_release+0x1bb/0x210
>>>>>>> [  738.358710]  exit_mmap+0x2f/0x1e0
>>>>>>> [  738.358723]  ? find_held_lock+0x34/0xa0
>>>>>>> [  738.358746]  mmput+0x39/0xe0
>>>>>>> [  738.358756]  do_exit+0x5c3/0xc00
>>>>>>> [  738.358763]  ? find_held_lock+0x34/0xa0
>>>>>>> [  738.358780]  do_group_exit+0x47/0xb0
>>>>>>> [  738.358791]  get_signal+0x15b/0xc50
>>>>>>> [  738.358807]  arch_do_signal_or_restart+0xaf/0x710
>>>>>>> [  738.358816]  ? lockdep_hardirqs_on_prepare+0xd4/0x180
>>>>>>> [  738.358822]  ? _raw_spin_unlock_irqrestore+0x39/0x40
>>>>>>> [  738.358831]  ? ktime_get_mono_fast_ns+0x50/0xa0
>>>>>>> [  738.358844]  ? amdgpu_drm_ioctl+0x6b/0x80 [amdgpu]
>>>>>>> [  738.359044]  exit_to_user_mode_prepare+0xf2/0x1b0
>>>>>>> [  738.359054]  syscall_exit_to_user_mode+0x19/0x60
>>>>>>> [  738.359062]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>>>>>> [  738.359069] RIP: 0033:0x7f6b89a51887
>>>>>>> [  738.359076] RSP: 002b:00007f6b82b54b18 EFLAGS: 00000246 ORIG_RAX:
>>>>>>> 0000000000000010
>>>>>>> [  738.359086] RAX: fffffffffffffe00 RBX: 00007f6b82b54b50 RCX: 00007f6b89a51887
>>>>>>> [  738.359091] RDX: 00007f6b82b54b50 RSI: 00000000c02064c3 RDI: 0000000000000007
>>>>>>> [  738.359096] RBP: 00000000c02064c3 R08: 0000000000000003 R09: 00007f6b82b54bbc
>>>>>>> [  738.359101] R10: 0000000000000001 R11: 0000000000000246 R12: 0000000165a0bc00
>>>>>>> [  738.359106] R13: 0000000000000007 R14: 0000000000000001 R15: 0000000000000000
>>>>>>> [  738.359129]
>>>>>>>                   Showing all locks held in the system:
>>>>>>> [  738.359141] 1 lock held by khungtaskd/54:
>>>>>>> [  738.359148]  #0: ffffffff829f6840 (rcu_read_lock){....}-{1:2}, at:
>>>>>>> debug_show_all_locks+0x15/0x183
>>>>>>> [  738.359187] 1 lock held by systemd-journal/174:
>>>>>>> [  738.359202] 1 lock held by MatrixMultiplic/653:
>>>>>>> [  738.359206]  #0: ffff88810e364fe0
>>>>>>> (&adev->notifier_lock){+.+.}-{3:3}, at:
>>>>>>> amdgpu_mn_invalidate_gfx+0x34/0xa0 [amdgpu]
>>>>>>>
>>>>>>> Daniel
>>>>>> _______________________________________________
>>>>>> dri-devel mailing list
>>>>>> dri-devel@...ts.freedesktop.org
>>>>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.freedesktop.org%2Fmailman%2Flistinfo%2Fdri-devel&amp;data=04%7C01%7Cchristian.koenig%40amd.com%7C81203e5bac5841b8e5a108d8c82087a9%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637479389339295622%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=RDSxD6OqD8HaOA2VnNfbJwLnKzhCLgOr5SVLjLF91bA%3D&amp;reserved=0
>>>>>
>>>
>>> --
>>> Daniel Vetter
>>> Software Engineer, Intel Corporation
>>> http://blog.ffwll.ch
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