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From: John Baldwin <jhb@FreeBSD.org>
Date: Fri, 11 Jun 2010 15:56:18 +0000 (UTC)
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Subject: svn commit: r209050 - head/sys/sys
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Author: jhb
Date: Fri Jun 11 15:56:18 2010
New Revision: 209050
URL: http://svn.freebsd.org/changeset/base/209050

Log:
  Add helper macros to iterate over available CPUs in the system.
  CPU_FOREACH(i) iterates over the CPU IDs of all available CPUs.  The
  CPU_FIRST() and CPU_NEXT(i) macros can also be used to iterate over
  available CPU IDs.  CPU_NEXT(i) wraps around to CPU_FIRST() rather than
  returning some sort of terminator.
  
  Requested by:	rwatson
  Reviewed by:	attilio

Modified:
  head/sys/sys/smp.h

Modified: head/sys/sys/smp.h
==============================================================================
--- head/sys/sys/smp.h	Fri Jun 11 15:55:18 2010	(r209049)
+++ head/sys/sys/smp.h	Fri Jun 11 15:56:18 2010	(r209050)
@@ -91,6 +91,44 @@ extern cpumask_t all_cpus;
  */
 #define	CPU_ABSENT(x_cpu)	((all_cpus & (1 << (x_cpu))) == 0)
 
+/*
+ * Macros to iterate over non-absent CPUs.  CPU_FOREACH() takes an
+ * integer iterator and iterates over the available set of CPUs.
+ * CPU_FIRST() returns the id of the first non-absent CPU.  CPU_NEXT()
+ * returns the id of the next non-absent CPU.  It will wrap back to
+ * CPU_FIRST() once the end of the list is reached.  The iterators are
+ * currently implemented via inline functions.
+ */
+#define	CPU_FOREACH(i)							\
+	for ((i) = 0; (i) <= mp_maxid; (i)++)				\
+		if (!CPU_ABSENT((i)))
+
+static __inline int
+cpu_first(void)
+{
+	int i;
+
+	for (i = 0;; i++)
+		if (!CPU_ABSENT(i))
+			return (i);
+}
+
+static __inline int
+cpu_next(int i)
+{
+
+	for (;;) {
+		i++;
+		if (i > mp_maxid)
+			i = 0;
+		if (!CPU_ABSENT(i))
+			return (i);
+	}
+}
+
+#define	CPU_FIRST()	cpu_first()
+#define	CPU_NEXT(i)	cpu_next((i))
+
 #ifdef SMP
 /*
  * Machine dependent functions used to initialize MP support.