Re: OOPS: 2.6.16-rc6 cpufreq_conservative

[Linus Torvalds <torvalds@osdl.org>]

On Sun, 19 Mar 2006, Andrew Morton wrote:
> 
> That's about the same saving as uninlining first_cpu() and next_cpu()
> provides.

Btw, we could do that better for UP too.

How does this patch look? It makes "for_each_cpu()" look the same 
regardless of whether it is UP/SMP, by simply making first_cpu() and 
next_cpu() work appropriately. 

No ugly macros this time ;)

		Linus

---
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 60e56c6..c8dbc24 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -212,17 +212,15 @@ static inline void __cpus_shift_left(cpu
 	bitmap_shift_left(dstp->bits, srcp->bits, n, nbits);
 }
 
-#define first_cpu(src) __first_cpu(&(src), NR_CPUS)
-static inline int __first_cpu(const cpumask_t *srcp, int nbits)
-{
-	return min_t(int, nbits, find_first_bit(srcp->bits, nbits));
-}
-
-#define next_cpu(n, src) __next_cpu((n), &(src), NR_CPUS)
-static inline int __next_cpu(int n, const cpumask_t *srcp, int nbits)
-{
-	return min_t(int, nbits, find_next_bit(srcp->bits, nbits, n+1));
-}
+#if NR_CPUS > 1
+extern int fastcall __first_cpu(const cpumask_t *srcp);
+extern int fastcall __next_cpu(int n, const cpumask_t *srcp);
+#define first_cpu(srcp) __first_cpu(&(srcp))
+#define next_cpu(n,srcp) __next_cpu((n),&(srcp))
+#else
+#define first_cpu(srcp)		(0)
+#define next_cpu(n, srcp)	((n)+1)
+#endif
 
 #define cpumask_of_cpu(cpu)						\
 ({									\
@@ -313,14 +311,10 @@ static inline void __cpus_remap(cpumask_
 	bitmap_remap(dstp->bits, srcp->bits, oldp->bits, newp->bits, nbits);
 }
 
-#if NR_CPUS > 1
 #define for_each_cpu_mask(cpu, mask)		\
 	for ((cpu) = first_cpu(mask);		\
 		(cpu) < NR_CPUS;		\
 		(cpu) = next_cpu((cpu), (mask)))
-#else /* NR_CPUS == 1 */
-#define for_each_cpu_mask(cpu, mask) for ((cpu) = 0; (cpu) < 1; (cpu)++)
-#endif /* NR_CPUS */
 
 /*
  * The following particular system cpumasks and operations manage
diff --git a/kernel/cpu.c b/kernel/cpu.c
index e882c6b..0a9cc97 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -10,6 +10,7 @@
 #include <linux/sched.h>
 #include <linux/unistd.h>
 #include <linux/cpu.h>
+#include <linux/cpumask.h>
 #include <linux/module.h>
 #include <linux/kthread.h>
 #include <linux/stop_machine.h>
@@ -20,6 +21,18 @@ static DECLARE_MUTEX(cpucontrol);
 
 static struct notifier_block *cpu_chain;
 
+int __first_cpu(const cpumask_t *srcp)
+{
+	return min_t(int, NR_CPUS, find_first_bit(srcp->bits, NR_CPUS));
+}
+EXPORT_SYMBOL(__first_cpu);
+
+int __next_cpu(int n, const cpumask_t *srcp)
+{
+	return min_t(int, NR_CPUS, find_next_bit(srcp->bits, NR_CPUS, n+1));
+}
+EXPORT_SYMBOL(__next_cpu);
+
 #ifdef CONFIG_HOTPLUG_CPU
 static struct task_struct *lock_cpu_hotplug_owner;
 static int lock_cpu_hotplug_depth;
-
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