Patchwork [v3,42/45] powerpc: Use get/put_online_cpus_atomic() to avoid false-positive warning

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Submitter Srivatsa S. Bhat
Date June 27, 2013, 8 p.m.
Message ID <>
Download mbox | patch
Permalink /patch/255156/
State Not Applicable
Delegated to: David Miller
Headers show


Srivatsa S. Bhat - June 27, 2013, 8 p.m.
Bringing a secondary CPU online is a special case in which, accessing
the cpu_online_mask is safe, even though that task (which running on the
CPU coming online) is not the hotplug writer.

It is a little hard to teach this to the debugging checks under
CONFIG_DEBUG_HOTPLUG_CPU. But luckily powerpc is one of the few places
where the CPU coming online traverses the cpu_online_mask before fully
coming online. So wrap that part under get/put_online_cpus_atomic(), to
avoid false-positive warnings from the CPU hotplug debug code.

Cc: Benjamin Herrenschmidt <>
Cc: Paul Mackerras <>
Cc: Kumar Gala <>
Cc: Zhao Chenhui <>
Cc: Thomas Gleixner <>
Signed-off-by: Srivatsa S. Bhat <>

 arch/powerpc/kernel/smp.c |    2 ++
 1 file changed, 2 insertions(+)

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diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 2123bec..59c9a09 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -657,6 +657,7 @@  __cpuinit void start_secondary(void *unused)
 		cpumask_set_cpu(base + i, cpu_core_mask(cpu));
 	l2_cache = cpu_to_l2cache(cpu);
+	get_online_cpus_atomic();
 	for_each_online_cpu(i) {
 		struct device_node *np = cpu_to_l2cache(i);
 		if (!np)
@@ -667,6 +668,7 @@  __cpuinit void start_secondary(void *unused)
+	put_online_cpus_atomic();