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-rw-r--r--kernel/cpu.c83
1 files changed, 49 insertions, 34 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c
index d61ba88f34e..e882c6babf4 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -16,47 +16,76 @@
#include <asm/semaphore.h>
/* This protects CPUs going up and down... */
-DECLARE_MUTEX(cpucontrol);
-EXPORT_SYMBOL_GPL(cpucontrol);
+static DECLARE_MUTEX(cpucontrol);
static struct notifier_block *cpu_chain;
-/*
- * Used to check by callers if they need to acquire the cpucontrol
- * or not to protect a cpu from being removed. Its sometimes required to
- * call these functions both for normal operations, and in response to
- * a cpu being added/removed. If the context of the call is in the same
- * thread context as a CPU hotplug thread, we dont need to take the lock
- * since its already protected
- * check drivers/cpufreq/cpufreq.c for its usage - Ashok Raj
- */
+#ifdef CONFIG_HOTPLUG_CPU
+static struct task_struct *lock_cpu_hotplug_owner;
+static int lock_cpu_hotplug_depth;
-int current_in_cpu_hotplug(void)
+static int __lock_cpu_hotplug(int interruptible)
{
- return (current->flags & PF_HOTPLUG_CPU);
+ int ret = 0;
+
+ if (lock_cpu_hotplug_owner != current) {
+ if (interruptible)
+ ret = down_interruptible(&cpucontrol);
+ else
+ down(&cpucontrol);
+ }
+
+ /*
+ * Set only if we succeed in locking
+ */
+ if (!ret) {
+ lock_cpu_hotplug_depth++;
+ lock_cpu_hotplug_owner = current;
+ }
+
+ return ret;
}
-EXPORT_SYMBOL_GPL(current_in_cpu_hotplug);
+void lock_cpu_hotplug(void)
+{
+ __lock_cpu_hotplug(0);
+}
+EXPORT_SYMBOL_GPL(lock_cpu_hotplug);
+void unlock_cpu_hotplug(void)
+{
+ if (--lock_cpu_hotplug_depth == 0) {
+ lock_cpu_hotplug_owner = NULL;
+ up(&cpucontrol);
+ }
+}
+EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
+
+int lock_cpu_hotplug_interruptible(void)
+{
+ return __lock_cpu_hotplug(1);
+}
+EXPORT_SYMBOL_GPL(lock_cpu_hotplug_interruptible);
+#endif /* CONFIG_HOTPLUG_CPU */
/* Need to know about CPUs going up/down? */
int register_cpu_notifier(struct notifier_block *nb)
{
int ret;
- if ((ret = down_interruptible(&cpucontrol)) != 0)
+ if ((ret = lock_cpu_hotplug_interruptible()) != 0)
return ret;
ret = notifier_chain_register(&cpu_chain, nb);
- up(&cpucontrol);
+ unlock_cpu_hotplug();
return ret;
}
EXPORT_SYMBOL(register_cpu_notifier);
void unregister_cpu_notifier(struct notifier_block *nb)
{
- down(&cpucontrol);
+ lock_cpu_hotplug();
notifier_chain_unregister(&cpu_chain, nb);
- up(&cpucontrol);
+ unlock_cpu_hotplug();
}
EXPORT_SYMBOL(unregister_cpu_notifier);
@@ -112,13 +141,6 @@ int cpu_down(unsigned int cpu)
goto out;
}
- /*
- * Leave a trace in current->flags indicating we are already in
- * process of performing CPU hotplug. Callers can check if cpucontrol
- * is already acquired by current thread, and if so not cause
- * a dead lock by not acquiring the lock
- */
- current->flags |= PF_HOTPLUG_CPU;
err = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
(void *)(long)cpu);
if (err == NOTIFY_BAD) {
@@ -171,7 +193,6 @@ out_thread:
out_allowed:
set_cpus_allowed(current, old_allowed);
out:
- current->flags &= ~PF_HOTPLUG_CPU;
unlock_cpu_hotplug();
return err;
}
@@ -182,7 +203,7 @@ int __devinit cpu_up(unsigned int cpu)
int ret;
void *hcpu = (void *)(long)cpu;
- if ((ret = down_interruptible(&cpucontrol)) != 0)
+ if ((ret = lock_cpu_hotplug_interruptible()) != 0)
return ret;
if (cpu_online(cpu) || !cpu_present(cpu)) {
@@ -190,11 +211,6 @@ int __devinit cpu_up(unsigned int cpu)
goto out;
}
- /*
- * Leave a trace in current->flags indicating we are already in
- * process of performing CPU hotplug.
- */
- current->flags |= PF_HOTPLUG_CPU;
ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
if (ret == NOTIFY_BAD) {
printk("%s: attempt to bring up CPU %u failed\n",
@@ -217,7 +233,6 @@ out_notify:
if (ret != 0)
notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu);
out:
- current->flags &= ~PF_HOTPLUG_CPU;
- up(&cpucontrol);
+ unlock_cpu_hotplug();
return ret;
}