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Subject[PATCH v6 19/46] irq: 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.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

kernel/irq/manage.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index e49a288..b4240b9 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -16,6 +16,7 @@
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/sched.h>
+#include <linux/cpu.h>
#include <linux/task_work.h>

#include "internals.h"
@@ -202,7 +203,9 @@ int irq_set_affinity(unsigned int irq, const struct cpumask *mask)
return -EINVAL;

raw_spin_lock_irqsave(&desc->lock, flags);
+ get_online_cpus_atomic();
ret = __irq_set_affinity_locked(irq_desc_get_irq_data(desc), mask);
+ put_online_cpus_atomic();
raw_spin_unlock_irqrestore(&desc->lock, flags);
return ret;
}
@@ -343,7 +346,9 @@ int irq_select_affinity_usr(unsigned int irq, struct cpumask *mask)
int ret;

raw_spin_lock_irqsave(&desc->lock, flags);
+ get_online_cpus_atomic();
ret = setup_affinity(irq, desc, mask);
+ put_online_cpus_atomic();
raw_spin_unlock_irqrestore(&desc->lock, flags);
return ret;
}
@@ -1126,7 +1131,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
}

/* Set default affinity mask once everything is setup */
+ get_online_cpus_atomic();
setup_affinity(irq, desc, mask);
+ put_online_cpus_atomic();

} else if (new->flags & IRQF_TRIGGER_MASK) {
unsigned int nmsk = new->flags & IRQF_TRIGGER_MASK;


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