linux-kernel - Re: [RESEND PATCH 2/3] bcache: update document info

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Date:	Fri, 1 Jul 2016 12:21:43 +0800
From:	Coly Li <colyli@...e.de>
To:	wangyijing <wangyijing@...wei.com>, Coly Li <i@...y.li>,
	axboe@...com, Kent Overstreet <kent.overstreet@...il.com>
Cc:	Eric Wheeler <git@...ux.ewheeler.net>,
	linux-bcache@...r.kernel.org, linux-raid@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH 2/3] bcache: update document info

在 16/7/1 上午9:51, wangyijing 写道:
> Hi Coly, thanks to your review and comments.
> 
> Commit 77b5a08427e875 ("bcache: don't embed 'return' statements in closure macros")
> remove the return in continue_at(), so I think we should update the document info
> about continue_at().
> 
> Thanks!
> Yijing.

Hi Yijing,

The original version of continue_at() returns to caller function inside
the macro, Jens thinks this macro breaks code execution flow implicitly,
so he moves 'return' out of continue_at() and to follow continue_at() at
the location where continue_at() is referenced.

So as I suggested, the original author means the code should return to
the calling function.

But YES, I agree that the comments should be updated, because there is
no 'return' inside macro continue_at(). We should explicitly point out
that there should be a 'return' immediately following macro continue_at().

Thanks.

Coly


> 在 2016/6/29 18:16, Coly Li 写道:
>> 在 16/6/22 上午10:12, Yijing Wang 写道:
>>> There is no return in continue_at(), update the documentation.
>>>
>>
>> There are 2 modification of this patch. The first one is about a typo,
>> it is correct.
>>
>> But I doubt your second modification is proper. The line removed in your
>> patch is,
>>> - * continue_at() also, critically, is a macro that returns the
>> calling function.
>>> - * There's good reason for this.
>>> - *
>>
>> I think this is exactly what original author wants to say. It does not
>> mean return a value, it means return to the calling function. And the
>> bellowed lines explains the reason.
>>
>>> Signed-off-by: Yijing Wang <wangyijing@...wei.com>
>>> ---
>>>  drivers/md/bcache/closure.c |    2 +-
>>>  drivers/md/bcache/closure.h |    3 ---
>>>  2 files changed, 1 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/md/bcache/closure.c b/drivers/md/bcache/closure.c
>>> index 9eaf1d6..864e673 100644
>>> --- a/drivers/md/bcache/closure.c
>>> +++ b/drivers/md/bcache/closure.c
>>> @@ -112,7 +112,7 @@ bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
>>>  EXPORT_SYMBOL(closure_wait);
>>>  
>>>  /**
>>> - * closure_sync - sleep until a closure a closure has nothing left to wait on
>>> + * closure_sync - sleep until a closure has nothing left to wait on
>>
>> Yes, this modification is good.
>>
>>>   *
>>>   * Sleeps until the refcount hits 1 - the thread that's running the closure owns
>>>   * the last refcount.
>>> diff --git a/drivers/md/bcache/closure.h b/drivers/md/bcache/closure.h
>>> index 782cc2c..f51188d 100644
>>> --- a/drivers/md/bcache/closure.h
>>> +++ b/drivers/md/bcache/closure.h
>>> @@ -31,9 +31,6 @@
>>>   * passing it, as you might expect, the function to run when nothing is pending
>>>   * and the workqueue to run that function out of.
>>>   *
>>> - * continue_at() also, critically, is a macro that returns the calling function.
>>> - * There's good reason for this.
>>> - *
>>>   * To use safely closures asynchronously, they must always have a refcount while
>>>   * they are running owned by the thread that is running them. Otherwise, suppose
>>>   * you submit some bios and wish to have a function run when they all complete:
>>>
>>
>>
>