linux-kernel - Re: [PATCH 4/4] futex: Add FUTEX_LOCK with optional adaptive spinning

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Date:	Fri, 7 May 2010 18:43:10 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Darren Hart <dvhltc@...ibm.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Eric Dumazet <eric.dumazet@...il.com>,
	"Peter W. Morreale" <pmorreale@...ell.com>,
	Rik van Riel <riel@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Gregory Haskins <ghaskins@...ell.com>,
	Sven-Thorsten Dietrich <sdietrich@...ell.com>,
	Chris Mason <chris.mason@...cle.com>,
	John Cooper <john.cooper@...rd-harmonic.com>,
	Chris Wright <chrisw@...s-sol.org>,
	Ulrich Drepper <drepper@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Avi Kivity <avi@...hat.com>
Subject: Re: [PATCH 4/4] futex: Add FUTEX_LOCK with optional adaptive
 spinning


On Fri, 7 May 2010, Peter Zijlstra wrote:

> On Fri, 2010-05-07 at 18:30 +0200, Thomas Gleixner wrote:
> > > Please keep the code as near mutex_spin_on_owner() as possible.
> > 
> > There is no reason why we can't make that unconditional.
> > 
> Sure, but lets do that in a separate series.

Sure. I'm not touching mutex_spin_on_owner() now. It's just for
testing now.

Thanks,

	tglx
---
Index: linux-2.6-tip/kernel/sched.c
===================================================================
--- linux-2.6-tip.orig/kernel/sched.c
+++ linux-2.6-tip/kernel/sched.c
@@ -841,6 +841,10 @@ static inline int task_running(struct rq
 
 static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
 {
+#ifdef CONFIG_SMP
+	next->oncpu = 1;
+	prev->oncpu = 0;
+#endif
 }
 
 static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
@@ -2628,7 +2632,7 @@ void sched_fork(struct task_struct *p, i
 	if (likely(sched_info_on()))
 		memset(&p->sched_info, 0, sizeof(p->sched_info));
 #endif
-#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
+#if defined(CONFIG_SMP)
 	p->oncpu = 0;
 #endif
 #ifdef CONFIG_PREEMPT
@@ -5250,7 +5254,7 @@ void __cpuinit init_idle(struct task_str
 	__set_task_cpu(idle, cpu);
 
 	rq->curr = rq->idle = idle;
-#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
+#if defined(CONFIG_SMP)
 	idle->oncpu = 1;
 #endif
 	raw_spin_unlock_irqrestore(&rq->lock, flags);
Index: linux-2.6-tip/include/linux/sched.h
===================================================================
--- linux-2.6-tip.orig/include/linux/sched.h
+++ linux-2.6-tip/include/linux/sched.h
@@ -1178,10 +1178,8 @@ struct task_struct {
 	int lock_depth;		/* BKL lock depth */
 
 #ifdef CONFIG_SMP
-#ifdef __ARCH_WANT_UNLOCKED_CTXSW
 	int oncpu;
 #endif
-#endif
 
 	int prio, static_prio, normal_prio;
 	unsigned int rt_priority;

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