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

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Date:	Fri, 28 Jun 2013 16:56:41 +1000
From:	Stephen Rothwell <sfr@...b.auug.org.au>
To:	Randy Dunlap <rdunlap@...radead.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	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)

Hi Guys,

On Thu, 27 Jun 2013 23:06:43 -0700 Randy Dunlap <rdunlap@...radead.org> wrote:
>
> 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...)

I added the following to linux-next today:
(sorry Randy, I forgot the Reported-by:, Andrew please add)

From: Stephen Rothwell <sfr@...b.auug.org.au>
Date: Fri, 28 Jun 2013 16:52:58 +1000
Subject: [PATCH] fix warnings from ?: operator in wait.h

Signed-off-by: Stephen Rothwell <sfr@...b.auug.org.au>
---
 include/linux/wait.h | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 1c08a6c..f3b793d 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -197,7 +197,12 @@ wait_queue_head_t *bit_waitqueue(void *, int);
 	for (;;) {							\
 		__ret = prepare_to_wait_event(&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;						\
 		}							\
 									\
@@ -218,9 +223,14 @@ wait_queue_head_t *bit_waitqueue(void *, int);
 #define wait_event_common(wq, condition, state, tout)			\
 ({									\
 	long __ret;							\
-	if (condition)							\
-		__ret = __wait_no_timeout(tout) ?: (tout) ?: 1;		\
-	else								\
+	if (condition) {						\
+		__ret = __wait_no_timeout(tout);			\
+		if (!__ret) {						\
+			__ret = (tout);					\
+			if (!__ret)					\
+				__ret = 1;				\
+		}							\
+	} else								\
 		__ret = __wait_event_common(wq, condition, state, tout);\
 	__ret;								\
 })
-- 
1.8.3.1

-- 
Cheers,
Stephen Rothwell                    sfr@...b.auug.org.au

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