[Intel-gfx] [RFC v2 02/12] drm/i915/svm: Runtime (RT) allocator support

[Niranjana Vishwanathapura]

On Tue, Dec 17, 2019 at 08:18:21PM +0000, Jason Gunthorpe wrote:
>On Fri, Dec 13, 2019 at 01:56:04PM -0800, Niranjana Vishwanathapura wrote:
>
>> +	ctx = i915_gem_context_lookup(file->driver_priv, args->rsvd1);
>> +	if (!ctx || !rcu_access_pointer(ctx->vm))
>> +		return -ENOENT;
>> +
>> +	rcu_read_lock();
>> +	vm = i915_vm_get(ctx->vm);
>> +	rcu_read_unlock();
>
>This looks like wrong use of RCU to me.
>
>Getting a rcu lock and not calling rcu_dereference under it is
>basically guarenteed to be wrong..
>

Oops, yah, I should be just calling i915_gem_context_get_vm_rcu().

Thanks,
Niranjana

>Jason