[PATCH] powerpc: Use cpumask iterator to avoid warning in xmon

Anton Blanchard anton at samba.org
Fri Jun 29 15:28:57 EST 2012

We have a bug report where the kernel hits a warning in the cpumask

WARNING: at include/linux/cpumask.h:107

Which is:
        WARN_ON_ONCE(cpu >= nr_cpumask_bits);

The backtrace is:

xmon is iterating through 0 to NR_CPUS. I'm not sure why we are still
open coding this but iterating above nr_cpu_ids is definitely a bug.

This patch iterates through all possible cpus, in case we issue a
system reset and CPUs in an offline state call in.

Perhaps the old code was trying to handle CPUs that were in the
partition but were never started (eg kexec into a kernel with an
nr_cpus= boot option). They are going to die way before we get into
xmon since we haven't set any kernel state up for them.

Signed-off-by: Anton Blanchard <anton at samba.org>  
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 0f3ab06..eab3492 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -971,7 +971,7 @@ static int cpu_cmd(void)
 		/* print cpus waiting or in xmon */
 		printf("cpus stopped:");
 		count = 0;
-		for (cpu = 0; cpu < NR_CPUS; ++cpu) {
+		for_each_possible_cpu(cpu) {
 			if (cpumask_test_cpu(cpu, &cpus_in_xmon)) {
 				if (count == 0)
 					printf(" %x", cpu);

More information about the Linuxppc-dev mailing list