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Subject[PATCH v6 18/46] softirq: Use get/put_online_cpus_atomic() to prevent CPU offline
Date
Once stop_machine() is gone from the CPU offline path, we won't be able to
depend on preempt_disable() or local_irq_disable() to prevent CPUs from
going offline from under us.

Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline,
while invoking from atomic context.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

kernel/softirq.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index ed567ba..98c3e27 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -631,6 +631,7 @@ static void remote_softirq_receive(void *data)

static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softirq)
{
+ get_online_cpus_atomic();
if (cpu_online(cpu)) {
cp->func = remote_softirq_receive;
cp->info = cp;
@@ -638,8 +639,10 @@ static int __try_remote_softirq(struct call_single_data *cp, int cpu, int softir
cp->priv = softirq;

__smp_call_function_single(cpu, cp, 0);
+ put_online_cpus_atomic();
return 0;
}
+ put_online_cpus_atomic();
return 1;
}
#else /* CONFIG_USE_GENERIC_SMP_HELPERS */


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