Re: [amdgpu] deadlock

From: Christian König
Date: Wed Feb 03 2021 - 09:39:39 EST

Hi Daniel,

I've talked a bit with our internal team.

The problem is that the 20.20 release still uses the older OpenCL stack which obviously has a bug here and causes a hang.

The best approach I can give you is to switch to the ROCm stack instead.

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