Re: [PATCH 16/16] io_uring: return back safer resurrect

[yangerkun <yangerkun@huawei.com>]

在 2021/5/10 17:15, Pavel Begunkov 写道:
> On 5/10/21 3:22 AM, yangerkun wrote:
>> 在 2021/4/11 8:46, Pavel Begunkov 写道:
>>> Revert of revert of "io_uring: wait potential ->release() on resurrect",
>>> which adds a helper for resurrect not racing completion reinit, as was
>>> removed because of a strange bug with no clear root or link to the
>>> patch.
>>>
>>> Was improved, instead of rcu_synchronize(), just wait_for_completion()
>>> because we're at 0 refs and it will happen very shortly. Specifically
>>> use non-interruptible version to ignore all pending signals that may
>>> have ended prior interruptible wait.
>>>
>>> This reverts commit cb5e1b81304e089ee3ca948db4d29f71902eb575.
>>>
>>> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
>>
>> I have a question. Compare with the logical before this patch. We need call reinit_completion(&ctx->ref_comp) to make sure the effective use of the ref_comp.
>>
>> Does we forget to do this? Or I miss something?
> If percpu_ref_tryget() there succeeds, it should have not called
> complete by design, otherwise it do complete once (+1 completion
> count) following with a single wait(-1 completion count), so +1 -1
> should return it back to zero. See how struct completion works,
> e.g. completion.rst, number of completions is counted inside.

Got it. Thanks for your explain!

> 
> btw, you have a strange mail encoding, apparently it's not Unicode

Yeah... I have change to Unicode!

Thanks,
Kun.
>