On Tue, May 15 2018, James Simmons wrote:
>> On Wed, May 02 2018, James Simmons wrote:
>>
>> > From: Lai Siyao <lai.siyao@xxxxxxxxx>
>> >
>> > Currently we set LU_OBJECT_HEARD_BANSHEE on object when we want
>> > to remove object from cache, but this may lead to deadlock, because
>> > when other process lookup such object, it needs to wait for this
>> > object until release (done at last refcount put), while that process
>> > maybe already hold an LDLM lock.
>> >
>> > Now that current code can handle dying object correctly, we can just
>> > return such object in lookup, thus the above deadlock can be avoided.
>>
>> I think one of the reasons that I didn't apply this to mainline myself
>> is that "Now that" comment. When is the "now" that it is referring to?
>> Are were sure that all code in mainline "can handle dying objects
>> correctly"??
>
> So I talked to Lai and he posted the LU-9049 ticket what patches need to
> land before this one. Only one patch is of concern and its for LU-9203
> which doesn't apply to the staging tree since we don't have the LNet SMP
> updates in our tree. I saved notes about making sure LU-9203 lands
> together with the future LNet SMP changes. As it stands it is safe to
> land to staging.
Thanks a lot for looking into this. Nice to have the safety of this
change confirmed.
What do you think of:
>> > @@ -713,36 +691,46 @@ struct lu_object *lu_object_find_at(const struct lu_env *env,
>> > * It is unnecessary to perform lookup-alloc-lookup-insert, instead,
>> > * just alloc and insert directly.
>> > *
>> > + * If dying object is found during index search, add @waiter to the
>> > + * site wait-queue and return ERR_PTR(-EAGAIN).
>>
>> It seems odd to add this comment here, when it seems to describe code
>> that is being removed.
>> I can see that this comment is added by the upstream patch
>> Commit: fa14bdf6b648 ("LU-9049 obdclass: change object lookup to no wait mode")
>> but I cannot see what it refers to.
>>
??
Am I misunderstanding something, or is that comment wrong?
Thanks,
NeilBrown
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