[Intel-gfx] [PATCH 22/66] drm/i915/gem: Bind the fence async for execbuf

[Chris Wilson]

Quoting Thomas Hellström (Intel) (2020-07-27 19:19:19)
> 
> On 7/15/20 1:51 PM, Chris Wilson wrote:
> > It is illegal to wait on an another vma while holding the vm->mutex, as
> > that easily leads to ABBA deadlocks (we wait on a second vma that waits
> > on us to release the vm->mutex). So while the vm->mutex exists, move the
> > waiting outside of the lock into the async binding pipeline.
> 
> Why is it we don't just move the fence binding to a separate loop after 
> unlocking the vm->mutex in eb_reserve_vm()?

That is what is done. The work is called immediately when possible. Just
the loop may be deferred if the what we need to unbind are still active.
-Chris