[PATCH v2 2/3] Mutually exclude cpu online and suspend/hibernate

[Srivatsa S. Bhat]

Don't allow cpu hotplug online operation and suspend/hibernate to run in
parallel. If suspend/hibernate has already started, fail the cpu online
operation.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
---

 kernel/cpu.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 12b7458..bc8c7d4 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -15,6 +15,7 @@
 #include <linux/stop_machine.h>
 #include <linux/mutex.h>
 #include <linux/gfp.h>
+#include <linux/suspend.h>
 
 #ifdef CONFIG_SMP
 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
@@ -366,6 +367,14 @@ int __cpuinit cpu_up(unsigned int cpu)
 	}
 #endif
 
+	/*
+	 * Prevent cpu online and suspend/hibernate (including freezer)
+	 * operations from running in parallel. Fail cpu online if suspend or
+	 * hibernate has already started.
+	 */
+	if (!trylock_pm_sleep())
+		return -EBUSY;
+
 	cpu_maps_update_begin();
 
 	if (cpu_hotplug_disabled) {
@@ -377,6 +386,7 @@ int __cpuinit cpu_up(unsigned int cpu)
 
 out:
 	cpu_maps_update_done();
+	unlock_pm_sleep();
 	return err;
 }
 

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