On 2017/06/21 10:45:41 -0700, Paul E. McKenney wrote:
> On Wed, Jun 21, 2017 at 07:55:34AM +0900, Akira Yokosawa wrote:
>> On 2017/06/20 23:28, Akira Yokosawa wrote:
>>> >From db0fd6b383b551eabecb12dfa21e42093f338b2f Mon Sep 17 00:00:00 2001
>>> From: Akira Yokosawa <akiyks@xxxxxxxxx>
>>> Date: Mon, 19 Jun 2017 23:55:31 +0900
>>> Subject: [PATCH 2/3] toyrcu: Trivial typo fixes (rcu_idx -> rcu_refcnt)
>>>
>>> Signed-off-by: Akira Yokosawa <akiyks@xxxxxxxxx>
>>> ---
>>> appendix/toyrcu/toyrcu.tex | 12 ++++++------
>>> 1 file changed, 6 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/appendix/toyrcu/toyrcu.tex b/appendix/toyrcu/toyrcu.tex
>>> index 79fbe33..a7bf6ca 100644
>>> --- a/appendix/toyrcu/toyrcu.tex
>>> +++ b/appendix/toyrcu/toyrcu.tex
>>> @@ -524,10 +524,10 @@ by complementing the value of \co{rcu_idx}, as in \co{rcu_idx = !rcu_idx}.
>>> Suppose that the old value of \co{rcu_idx} was zero, so that the new
>>> value is one.
>>> New readers that arrive after the complement operation will increment
>>> -\co{rcu_idx[1]}, while the old readers that previously incremented
>>> -\co{rcu_idx[0]} will decrement \co{rcu_idx[0]} when they exit their
>>> +\co{rcu_refcnt[1]}, while the old readers that previously incremented
>>> +\co{rcu_refcnt[0]} will decrement \co{rcu_refcnt[0]} when they exit their
>>> RCU read-side critical sections.
>>> -This means that the value of \co{rcu_idx[0]} will no longer be incremented,
>>> +This means that the value of \co{rcu_refcnt[0]} will no longer be incremented,
>>> and thus will be monotonically decreasing.\footnote{
>>> There is a race condition that this ``monotonically decreasing''
>>> statement ignores.
>>> @@ -616,11 +616,11 @@ Lines~6 and 19 acquire and release \co{rcu_gp_lock} in order to
>>> prevent more than one concurrent instance of \co{synchronize_rcu()}.
>>> Lines~7-8 pick up the value of \co{rcu_idx} and complement it,
>>> respectively, so that subsequent instances of \co{rcu_read_lock()}
>>> -will use a different element of \co{rcu_idx} that did preceding
>>> +will use a different element of \co{rcu_refcnt} that did preceding
>>> instances.
>>
>> I have a little trouble with this sentence. Do you mean:
>>
>> ..., so that subsequent instances of \co{rcu_read_lock()}
>> will use a different element of \co{rcu_refcnt} from the one did preceding
>> instances.
>
> Just to fully illustrate:
>
> 1. Suppose that rcu_idx is initially zero.
>
> 2. Any rcu_read_lock() invocations running at this point will
> therefore be incrementing rcu_refcnt[0].
>
> 3. A synchronize_srcu() instance now complements rcu_idx, so that
> its new value is one.
>
> 4. Any rcu_read_lock() invocations from step 2 that fetched rcu_idx
> before step 3 completed will still increment rcu_refcnt[0].
>
> 5. However, any subsequent rcu_read_lock() invocations will instead
> increment rcu_refcnt[1]. (At least until the next invocation
> of synchronize_rcu().)
>
> Does that help, or am I missing the point of your question?
Thanks. This is what I guessed you mean.
So what bothered me was the structure of the clause. I rarely see a sentence like:
I will buy a different model of PC that did you.
I can't figure out the grammatical role of "that" here.
Thanks, Akira
>
> Thanx, Paul
>
>> ???
>>
>> Thanks, Akira
>>> -Lines~10-12 then wait for the prior element of \co{rcu_idx} to
>>> +Lines~10-12 then wait for the prior element of \co{rcu_refcnt} to
>>> reach zero, with the memory barrier on line~9 ensuring that the check
>>> -of \co{rcu_idx} is not reordered to precede the complementing of
>>> +of \co{rcu_refcnt} is not reordered to precede the complementing of
>>> \co{rcu_idx}.
>>> Lines~13-18 repeat this process, and line~20 ensures that any
>>> subsequent reclamation operations are not reordered to precede the
>>>
>>
>
>
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