[PATCH 42/45] powerpc: Use get/put_online_cpus_atomic() to avoidfalse-positive warning

From: Srivatsa S. Bhat
Date: Sun Jun 23 2013 - 09:51:06 EST

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 <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Kumar Gala <galak@xxxxxxxxxxxxxxxxxxx>
Cc: Zhao Chenhui <chenhui.zhao@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>

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

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();


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