linux-kernel - [PATCH v5 18/45] irq: Use get/put_online_cpus

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Date:	Tue, 22 Jan 2013 13:08:00 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	tglx@...utronix.de, peterz@...radead.org, tj@...nel.org,
	oleg@...hat.com, paulmck@...ux.vnet.ibm.com, rusty@...tcorp.com.au,
	mingo@...nel.org, akpm@...ux-foundation.org, namhyung@...nel.org
Cc:	rostedt@...dmis.org, wangyun@...ux.vnet.ibm.com,
	xiaoguangrong@...ux.vnet.ibm.com, rjw@...k.pl, sbw@....edu,
	fweisbec@...il.com, linux@....linux.org.uk,
	nikunj@...ux.vnet.ibm.com, srivatsa.bhat@...ux.vnet.ibm.com,
	linux-pm@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, netdev@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v5 18/45] irq: Use get/put_online_cpus_atomic() to prevent CPU
 offline

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@...ux.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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