[PATCH] cpu/hotplug: handle unbalanced hotplug enable/disable

[Lianwei Wang]

Currently it just print a warning message but did not
reset cpu_hotplug_disabled when the enable/disable is
unbalanced. The unbalanced enable/disable will lead
the cpu hotplug work abnormally.

Reset it to 0 when an unablanced enable detected.

Signed-off-by: Lianwei Wang <lianwei.w...@gmail.com>
---
 kernel/cpu.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 6ea42e8da861..fef6caed77a3 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -243,6 +243,19 @@ void cpu_hotplug_done(void)
        cpuhp_lock_release();
 }
 
+static void _cpu_hotplug_disable(void)
+{
+       cpu_hotplug_disabled++;
+}
+
+static void _cpu_hotplug_enable(void)
+{
+       if (--cpu_hotplug_disabled < 0) {
+               WARN(1, "unbalanced hotplug enable %d\n", cpu_hotplug_disabled);
+               cpu_hotplug_disabled = 0;
+       }
+}
+
 /*
  * Wait for currently running CPU hotplug operations to complete (if any) and
  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
@@ -253,7 +266,7 @@ void cpu_hotplug_done(void)
 void cpu_hotplug_disable(void)
 {
        cpu_maps_update_begin();
-       cpu_hotplug_disabled++;
+       _cpu_hotplug_disable();
        cpu_maps_update_done();
 }
 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
@@ -261,7 +274,7 @@ EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
 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);
@@ -1053,7 +1066,7 @@ int disable_nonboot_cpus(void)
         * this even in case of failure as all disable_nonboot_cpus() users are
         * supposed to do enable_nonboot_cpus() on the failure path.
         */
-       cpu_hotplug_disabled++;
+       _cpu_hotplug_disable();
 
        cpu_maps_update_done();
        return error;
@@ -1073,7 +1086,7 @@ 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;
 
-- 
1.9.1