linux-kernel - [PATCH v6 34/46] hexagon/smp: Use get/put_online_cpus

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Date:	Mon, 18 Feb 2013 18:13:06 +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,
	walken@...gle.com, vincent.guittot@...aro.org
Subject: [PATCH v6 34/46] hexagon/smp: 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.

Cc: Richard Kuo <rkuo@...eaurora.org>
Cc: linux-hexagon@...r.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
---

 arch/hexagon/kernel/smp.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/hexagon/kernel/smp.c b/arch/hexagon/kernel/smp.c
index 8e095df..ec87de9 100644
--- a/arch/hexagon/kernel/smp.c
+++ b/arch/hexagon/kernel/smp.c
@@ -112,6 +112,7 @@ void send_ipi(const struct cpumask *cpumask, enum ipi_message_type msg)
 	unsigned long cpu;
 	unsigned long retval;
 
+	get_online_cpus_atomic();
 	local_irq_save(flags);
 
 	for_each_cpu(cpu, cpumask) {
@@ -128,6 +129,7 @@ void send_ipi(const struct cpumask *cpumask, enum ipi_message_type msg)
 	}
 
 	local_irq_restore(flags);
+	put_online_cpus_atomic();
 }
 
 static struct irqaction ipi_intdesc = {
@@ -241,9 +243,12 @@ void smp_send_reschedule(int cpu)
 void smp_send_stop(void)
 {
 	struct cpumask targets;
+
+	get_online_cpus_atomic();
 	cpumask_copy(&targets, cpu_online_mask);
 	cpumask_clear_cpu(smp_processor_id(), &targets);
 	send_ipi(&targets, IPI_CPU_STOP);
+	put_online_cpus_atomic();
 }
 
 void arch_send_call_function_single_ipi(int cpu)

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