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

[Pavel Begunkov <asml.silence@gmail.com>]

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.

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

-- 
Pavel Begunkov