UPSTREAM: cpu/hotplug: Handle unbalanced hotplug enable/disable

(cherry picked from commit 01b41159066531cc8d664362ff0cd89dd137bbfa)

When cpu_hotplug_enable() is called unbalanced w/o a preceeding
cpu_hotplug_disable() the code emits a warning, but happily decrements the
disabled counter. This causes the next operations to malfunction.

Prevent the decrement and just emit a warning.

Signed-off-by: Lianwei Wang <lianwei.wang@gmail.com>
Cc: peterz@infradead.org
Cc: linux-pm@vger.kernel.org
Cc: oleg@redhat.com
Link: http://lkml.kernel.org/r/1465541008-12476-1-git-send-email-lianwei.wang@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 9ced7c7516481f05549c48e6b2d3ae1bf5f36f61..c8a1751be2244233f7ebeea0db601593b3e468a3 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -185,10 +185,17 @@ void cpu_hotplug_disable(void)
 }
 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
 
+static void __cpu_hotplug_enable(void)
+{
+       if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
+               return;
+       cpu_hotplug_disabled--;
+}
+
 void cpu_hotplug_enable(void)
 {
        cpu_maps_update_begin();
-       WARN_ON(--cpu_hotplug_disabled < 0);
+       __cpu_hotplug_enable();
        cpu_maps_update_done();
 }
 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
@@ -631,7 +638,7 @@ void enable_nonboot_cpus(void)
 
        /* Allow everyone to use the CPU hotplug again */
        cpu_maps_update_begin();
-       WARN_ON(--cpu_hotplug_disabled < 0);
+       __cpu_hotplug_enable();
        if (cpumask_empty(frozen_cpus))
                goto out;