Yes, this can work using the same way as dqm_lock. This is trivial part,
Felix and Christian is discussing the solution of lock problem.
Regards,
Philip
On 2019-11-28 7:35 p.m., Zeng, Oak wrote:
[AMD Official Use Only - Internal Distribution Only]
Is kmalloc with GFP_NOWAIT an option here?
Regards,
Oak
*From:* amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> *On Behalf Of *
Sierra Guiza, Alejandro (Alex)
*Sent:* Wednesday, November 27, 2019 9:55 AM
*To:* Koenig, Christian <Christian.Koenig@xxxxxxx>; Kuehling, Felix
<Felix.Kuehling@xxxxxxx>
*Cc:* amd-gfx@xxxxxxxxxxxxxxxxxxxxx
*Subject:* Deadlock on PTEs update for HMM
Hi Christian,
As you know, we’re working on the HMM enablement. Im working on the dGPU
page table entries invalidation on the userptr mapping case. Currently,
the MMU notifiers handle stops all user mode queues, schedule a delayed
worker to re-validate userptr mappings and restart the queues.
Part of the HMM functionality, we need to invalidate the page table
entries instead of stopping the queues. At the same time we need to move
the revalidation of the userptr mappings into the page fault handler.
We’re seeing a deadlock warning after we try to invalidate the PTEs
inside the MMU notifier handler. More specific, when we try to update
the BOs to invalidate PTEs using amdgpu_vm_bo_update. This uses kmalloc
on the amdgpu_job_alloc which seems to be causing this problem.
Based on @Kuehling, Felix <mailto:Felix.Kuehling@xxxxxxx> comments,
kmalloc without any special flags can cause memory reclaim. Doing that
inside an MMU notifier is problematic, because an MMU notifier may be
called inside a memory-reclaim operation itself. That would result in
recursion. Also, reclaim shouldn't be done while holding a lock that can
be taken in an MMU notifier for the same reason. If you cause a reclaim
while holding that lock, then an MMU notifier called by the reclaim
can deadlock trying to take the same lock.
Please let us know if you have any advice to enable this the right way
Thanks in advanced,
Alejandro
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