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Date:   Wed, 3 Feb 2021 13:24:42 +0100
From:   Daniel Vetter <daniel@ffwll.ch>
To:     christian.koenig@amd.com
Cc:     Daniel Gomez <daniel@qtec.com>, Daniel Vetter <daniel@ffwll.ch>,
        Alex Deucher <alexander.deucher@amd.com>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [amdgpu] deadlock
Message-ID: <YBqWCgTPTLomYvAt@phenom.ffwll.local>
Mail-Followup-To: christian.koenig@amd.com, Daniel Gomez <daniel@qtec.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
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On Wed, Feb 03, 2021 at 01:21:20PM +0100, Christian König wrote:
> Am 03.02.21 um 12:45 schrieb Daniel Gomez:
> > On Wed, 3 Feb 2021 at 10:47, Daniel Gomez <daniel@qtec.com> wrote:
> > > On Wed, 3 Feb 2021 at 10:17, Daniel Vetter <daniel@ffwll.ch> wrote:
> > > > On Wed, Feb 3, 2021 at 9:51 AM Christian König <christian.koenig@amd.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@amd.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.

Yeah, but there's also no other driver that could cause a stuck dma_fence,
so why is reset not cleaning up the mess here? Irrespective of why the gpu
is stuck, the kernel should at least complete all the dma_fences even if
the gpu for some reason is terminally ill ...
-Daniel

> 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@qt5222:~# 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@lists.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
> > _______________________________________________
> > amd-gfx mailing list
> > amd-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/amd-gfx
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch