linux-kernel - Re: linux-next: Tree for Jun 28 [ BISECTED: rsyslog/imklog: High CPU usage ]

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Message-ID: <20130630181945.GA5171@redhat.com>
Date:	Sun, 30 Jun 2013 20:19:45 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Sedat Dilek <sedat.dilek@...il.com>
Cc:	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Imre Deak <imre.deak@...el.com>,
	Lukas Czerner <lczerner@...hat.com>,
	Samuel Ortiz <samuel@...tiz.org>,
	Wensong Zhang <wensong@...ux-vs.org>,
	Simon Horman <horms@...ge.net.au>,
	Julian Anastasov <ja@....bg>,
	Ralf Baechle <ralf@...ux-mips.org>, Valdis.Kletnieks@...edu
Subject: Re: linux-next: Tree for Jun 28 [ BISECTED: rsyslog/imklog: High
	CPU usage ]

Andrew, please drop these

	wait-introduce-wait_event_commonwq-condition-state-timeout.patch
	wait-introduce-prepare_to_wait_event.patch

patches again. I'll send v3 although it really looks like I should
never try to touch wait.h.

On 06/29, Sedat Dilek wrote:
>
> As this all did not show me what caused the problem I started a
> git-bisect session.
>
> This revealed the following culprit commit:
>
>      commit bb1f30cb7d3ba21098f0ee7e0382160ba2599a43
>      "wait: introduce wait_event_common(wq, condition, state, timeout)"

Heh. First of all, I am really sorry.

Not only "__wait_no_timeout(tout) ?:" was wrong, I didn't bother
to recheck this logic even after I got the "warning: the omitted
middle operand in ?:" reports.

Sedat, thanks you very much! Any chance you can try the patch below?

Oleg.


--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -191,12 +191,8 @@ wait_queue_head_t *bit_waitqueue(void *, int);
 	for (;;) {							\
 		__ret = prepare_to_wait_event(&wq, &__wait, state);	\
 		if (condition) {					\
-			__ret = __wait_no_timeout(tout);		\
-			if (!__ret) {					\
-				__ret = __tout;				\
-				if (!__ret)				\
-					__ret = 1;			\
-			}						\
+			__ret = __wait_no_timeout(tout) ? 0 :		\
+							(__tout ?: 1);	\
 			break;						\
 		}							\
 									\
@@ -217,16 +213,10 @@ 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);			\
-		if (!__ret) {						\
-			__ret = tout;					\
-			if (!__ret)					\
-				__ret = 1;				\
-		}							\
-	} else {							\
+	if (condition)							\
+		__ret = __wait_no_timeout(tout) ? 0 : ((tout) ?: 1);	\
+	else								\
 		__ret = __wait_event_common(wq, condition, state, tout);\
-	}								\
 	__ret;								\
 })
 

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