linux-kernel - [PATCH v5 42/45] tile: Use get/put_online_cpus

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Date:	Tue, 22 Jan 2013 13:14:35 +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 42/45] tile: 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: Chris Metcalf <cmetcalf@...era.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
---

 arch/tile/kernel/smp.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/tile/kernel/smp.c b/arch/tile/kernel/smp.c
index cbc73a8..fb30624 100644
--- a/arch/tile/kernel/smp.c
+++ b/arch/tile/kernel/smp.c
@@ -15,6 +15,7 @@
  */
 
 #include <linux/smp.h>
+#include <linux/cpu.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/irq.h>
@@ -82,9 +83,12 @@ void send_IPI_many(const struct cpumask *mask, int tag)
 void send_IPI_allbutself(int tag)
 {
 	struct cpumask mask;
+
+	get_online_cpus_atomic();
 	cpumask_copy(&mask, cpu_online_mask);
 	cpumask_clear_cpu(smp_processor_id(), &mask);
 	send_IPI_many(&mask, tag);
+	put_online_cpus_atomic();
 }
 
 /*

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