linux-kernel - Re: [PATCH 4/7] sched: Add a preempt count base offset to __might

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Date:	Thu, 16 Jul 2009 16:34:53 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 4/7] sched: Add a preempt count base offset to
 __might_sleep()

On Thu, 2009-07-16 at 16:14 +0200, Peter Zijlstra wrote:
> On Thu, 2009-07-16 at 02:28 -0400, Frederic Weisbecker wrote:
> > +++ b/include/linux/hardirq.h
> > @@ -103,6 +103,13 @@
> >   */
> >  #define in_atomic()    ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_INATOMIC_BASE)
> >  
> > +static inline int current_preempt_equals(int preempt_offset)
> > +{
> > +       int nested = preempt_count() & ~PREEMPT_ACTIVE;
> > +
> > +       return (nested == PREEMPT_INATOMIC_BASE + preempt_offset);
> > +}
> 
> I'm not sure about it being in hardirq.h, I think we should keep this in
> sched.c.
> 
> Also, I'm not sure about the name, but then I suck at naming too. How
> about something like: preempt_count_equals() ?
> 
> Other than that the series looks nice and I've got it queued.

I've added this on top:

---
Index: linux-2.6/include/linux/hardirq.h
===================================================================
--- linux-2.6.orig/include/linux/hardirq.h
+++ linux-2.6/include/linux/hardirq.h
@@ -103,13 +103,6 @@
  */
 #define in_atomic()	((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_INATOMIC_BASE)
 
-static inline int current_preempt_equals(int preempt_offset)
-{
-	int nested = preempt_count() & ~PREEMPT_ACTIVE;
-
-	return (nested == PREEMPT_INATOMIC_BASE + preempt_offset);
-}
-
 /*
  * Check whether we were atomic before we did preempt_disable():
  * (used by the scheduler, *after* releasing the kernel lock)
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -9444,12 +9444,19 @@ void __init sched_init(void)
 }
 
 #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
+static inline int preempt_count_equals(int preempt_offset)
+{
+	int nested = preempt_count() & ~PREEMPT_ACTIVE;
+
+	return (nested == PREEMPT_INATOMIC_BASE + preempt_offset);
+}
+
 void __might_sleep(char *file, int line, int preempt_offset)
 {
 #ifdef in_atomic
 	static unsigned long prev_jiffy;	/* ratelimiting */
 
-	if ((current_preempt_equals(preempt_offset) && !irqs_disabled()) ||
+	if ((preempt_count_equals(preempt_offset) && !irqs_disabled()) ||
 	    system_state != SYSTEM_RUNNING || oops_in_progress)
 		return;
 	if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)


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