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Date: Mon, 24 May 2004 11:15:04 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Davide Libenzi <davidel@xmailserver.org>,
       Linux Kernel List <linux-kernel@vger.kernel.org>,
       rmk+lkml@arm.linux.org.uk
Subject: Re: scheduler: IRQs disabled over context switches
Message-ID: <20040524091504.GC26183@elte.hu>
References: <20040523174359.A21153@flint.arm.linux.org.uk> <20040524083715.GA24967@elte.hu> <Pine.LNX.4.58.0405232340070.2676@bigblue.dev.mdolabs.com> <20040524090538.GA26183@elte.hu> <40B19FF8.2050402@yahoo.com.au>
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* Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> >+# define prepare_arch_switch(rq, next)				\
> >+		do {						\
> >+			spin_lock(&(next)->switch_lock);	\
> >+			spin_unlock(&(rq)->lock);		\
> 
> spin_unlock_irq?

and spin_unlock in the finish_arch_switch() case, instead of
spin_unlock_irq. New patch below.

	Ingo

--- linux/kernel/sched.c.orig	
+++ linux/kernel/sched.c	
@@ -247,9 +247,15 @@ static DEFINE_PER_CPU(struct runqueue, r
  * Default context-switch locking:
  */
 #ifndef prepare_arch_switch
-# define prepare_arch_switch(rq, next)	do { } while (0)
-# define finish_arch_switch(rq, next)	spin_unlock_irq(&(rq)->lock)
-# define task_running(rq, p)		((rq)->curr == (p))
+# define prepare_arch_switch(rq, next)				\
+		do {						\
+			spin_lock(&(next)->switch_lock);	\
+			spin_unlock_irq(&(rq)->lock);		\
+		} while (0)
+# define finish_arch_switch(rq, prev) \
+		spin_unlock(&(prev)->switch_lock)
+# define task_running(rq, p) \
+		((rq)->curr == (p) || spin_is_locked(&(p)->switch_lock))
 #endif
 
 /*