linux-kernel - Re: mmotm 2013-06-27-16-36 uploaded (wait event common)

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Date:	Thu, 27 Jun 2013 23:06:43 -0700
From:	Randy Dunlap <rdunlap@...radead.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	mm-commits@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	linux-next@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>
Subject: Re: mmotm 2013-06-27-16-36 uploaded (wait event common)

On 06/27/13 22:51, Andrew Morton wrote:
> On Thu, 27 Jun 2013 22:30:41 -0700 Randy Dunlap <rdunlap@...radead.org> wrote:
> 
>> On 06/27/13 16:37, akpm@...ux-foundation.org wrote:
>>> The mm-of-the-moment snapshot 2013-06-27-16-36 has been uploaded to
>>>
>>>    http://www.ozlabs.org/~akpm/mmotm/
>>>
>>> mmotm-readme.txt says
>>>
>>> README for mm-of-the-moment:
>>>
>>> http://www.ozlabs.org/~akpm/mmotm/
>>>
>>
>> My builds are littered with hundreds of warnings like this one:
>>
>> drivers/tty/tty_ioctl.c:220:6: warning: the omitted middle operand in ?: will always be 'true', suggest explicit middle operand [-Wparentheses]
>>
>> I guess due to this line from wait_event_common():
>>
>> +		__ret = __wait_no_timeout(tout) ?: (tout) ?: 1;
>>
> 
> Ah, sorry, I missed that.  Had I noticed it, I would have spat it back
> on taste grounds alone, it being unfit for human consumption.
> 
> Something like this?
> 
> --- a/include/linux/wait.h~wait-introduce-wait_event_commonwq-condition-state-timeout-fix
> +++ a/include/linux/wait.h
> @@ -196,7 +196,11 @@ wait_queue_head_t *bit_waitqueue(void *,
>  	for (;;) {							\
>  		prepare_to_wait(&wq, &__wait, state);			\
>  		if (condition) {					\
> -			__ret = __wait_no_timeout(tout) ?: __tout ?: 1;	\
> +			__ret = __wait_no_timeout(tout);		\
> +			if (!__ret)					\
> +				__ret = __tout;				\
> +				if (!__ret)				\
> +					__ret = 1;			\
>  			break;						\
>  		}							\
>  									\
> 
> 

That does reduce the number of warnings, but the wait_event_common() macro
needs similar treatment.  I.e., I am still getting those warnings, just not
quite as many. (down from 2 per source code line to 1 per source code line
which contains some kind of wait...)

-- 
~Randy
--
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