[PATCH] sched_domain debugging

From: Nick Piggin <piggin@cyberone.com.au>

Anton was attempting to make a sched domain topology for his POWER5 and was
having some trouble.

This patch only includes code which is ifdefed out, but hopefully it will
be of some use to implementors.

Documentation/sched-domains.txt

@@ -46,3 +46,10 @@ The implementor should read comments in include/linux/sched.h:
 struct sched_domain fields, SD_FLAG_*, SD_*_INIT to get an idea of
 the specifics and what to tune.
 
+Implementors should change the line
+#undef SCHED_DOMAIN_DEBUG
+to
+#define SCHED_DOMAIN_DEBUG
+in kernel/sched.c as this enables an error checking parse of the sched domains
+which should catch most possible errors (described above). It also prints out
+the domain structure in a visual format.

kernel/sched.c

@@ -3395,9 +3395,87 @@ static void __init arch_init_sched_domains(void)
 #endif /* CONFIG_NUMA */
 #endif /* ARCH_HAS_SCHED_DOMAIN */
 
+#undef SCHED_DOMAIN_DEBUG
+#ifdef SCHED_DOMAIN_DEBUG
+void sched_domain_debug(void)
+{
+	int i;
+
+	for_each_cpu(i) {
+		int level = 0;
+		struct sched_domain *cpu_domain = cpu_sched_domain(i);
+
+		printk(KERN_DEBUG "CPU%d: %s\n",
+				i, (cpu_online(i) ? " online" : "offline"));
+
+		do {
+			int j;
+			char str[NR_CPUS];
+			struct sched_group *group = cpu_domain->groups;
+			cpumask_t groupmask, tmp;
+
+			cpumask_snprintf(str, NR_CPUS, cpu_domain->span);
+			cpus_clear(groupmask);
+
+			printk(KERN_DEBUG);
+			for (j = 0; j < level + 1; j++)
+				printk(" ");
+			printk("domain %d: span %s\n", level, str);
+
+			if (!cpu_isset(i, cpu_domain->span))
+				printk(KERN_DEBUG "ERROR domain->span does not contain CPU%d\n", i);
+			if (!cpu_isset(i, group->cpumask))
+				printk(KERN_DEBUG "ERROR domain->groups does not contain CPU%d\n", i);
+
+			printk(KERN_DEBUG);
+			for (j = 0; j < level + 2; j++)
+				printk(" ");
+			printk("groups:");
+			do {
+				if (group == NULL) {
+					printk(" ERROR: NULL");
+					break;
+				}
+
+				if (cpus_weight(group->cpumask) == 0)
+					printk(" ERROR empty group:");
+
+				cpus_and(tmp, groupmask, group->cpumask);
+				if (cpus_weight(tmp) > 0)
+					printk(" ERROR repeated CPUs:");
+
+				cpus_or(groupmask, groupmask, group->cpumask);
+
+				cpumask_snprintf(str, NR_CPUS, group->cpumask);
+				printk(" %s", str);
+
+				group = group->next;
+			} while (group != cpu_domain->groups);
+			printk("\n");
+
+			if (!cpus_equal(cpu_domain->span, groupmask))
+				printk(KERN_DEBUG "ERROR groups don't span domain->span\n");
+
+			level++;
+			cpu_domain = cpu_domain->parent;
+
+			if (cpu_domain) {
+				cpus_and(tmp, groupmask, cpu_domain->span);
+				if (!cpus_equal(tmp, groupmask))
+					printk(KERN_DEBUG "ERROR parent span is not a superset of domain->span\n");
+			}
+
+		} while (cpu_domain);
+	}
+}
+#else
+#define sched_domain_debug() {}
+#endif
+
 void __init sched_init_smp(void)
 {
 	arch_init_sched_domains();
+	sched_domain_debug();
 }
 #else
 void __init sched_init_smp(void)