cpu-hotplug: replace lock_cpu_hotplug() with get_online_cpus()

Replace all lock_cpu_hotplug/unlock_cpu_hotplug from the kernel and use
get_online_cpus and put_online_cpus instead as it highlights the
refcount semantics in these operations.

The new API guarantees protection against the cpu-hotplug operation, but
it doesn't guarantee serialized access to any of the local data
structures. Hence the changes needs to be reviewed.

In case of pseries_add_processor/pseries_remove_processor, use
cpu_maps_update_begin()/cpu_maps_update_done() as we're modifying the
cpu_present_map there.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 12 insertions, 12 deletions

diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index 3b20613..beb45c9 100644
--- a/arch/x86/kernel/cpu/mtrr/main.c
+++ b/arch/x86/kernel/cpu/mtrr/main.c
@@ -349,7 +349,7 @@ int mtrr_add_page(unsigned long base, unsigned long size,
 	replace = -1;
 
 	/* No CPU hotplug when we change MTRR entries */
-	lock_cpu_hotplug();
+	get_online_cpus();
 	/*  Search for existing MTRR  */
 	mutex_lock(&mtrr_mutex);
 	for (i = 0; i < num_var_ranges; ++i) {
@@ -405,7 +405,7 @@ int mtrr_add_page(unsigned long base, unsigned long size,
 	error = i;
  out:
 	mutex_unlock(&mtrr_mutex);
-	unlock_cpu_hotplug();
+	put_online_cpus();
 	return error;
 }
 
@@ -495,7 +495,7 @@ int mtrr_del_page(int reg, unsigned long base, unsigned long size)
 
 	max = num_var_ranges;
 	/* No CPU hotplug when we change MTRR entries */
-	lock_cpu_hotplug();
+	get_online_cpus();
 	mutex_lock(&mtrr_mutex);
 	if (reg < 0) {
 		/*  Search for existing MTRR  */
@@ -536,7 +536,7 @@ int mtrr_del_page(int reg, unsigned long base, unsigned long size)
 	error = reg;
  out:
 	mutex_unlock(&mtrr_mutex);
-	unlock_cpu_hotplug();
+	put_online_cpus();
 	return error;
 }
 /**
diff --git a/arch/x86/kernel/microcode.c b/arch/x86/kernel/microcode.c
index 09c3152..40cfd54 100644
--- a/arch/x86/kernel/microcode.c
+++ b/arch/x86/kernel/microcode.c
@@ -436,7 +436,7 @@ static ssize_t microcode_write (struct file *file, const char __user *buf, size_
 		return -EINVAL;
 	}
 
-	lock_cpu_hotplug();
+	get_online_cpus();
 	mutex_lock(&microcode_mutex);
 
 	user_buffer = (void __user *) buf;
@@ -447,7 +447,7 @@ static ssize_t microcode_write (struct file *file, const char __user *buf, size_
 		ret = (ssize_t)len;
 
 	mutex_unlock(&microcode_mutex);
-	unlock_cpu_hotplug();
+	put_online_cpus();
 
 	return ret;
 }
@@ -658,14 +658,14 @@ static ssize_t reload_store(struct sys_device *dev, const char *buf, size_t sz)
 
 		old = current->cpus_allowed;
 
-		lock_cpu_hotplug();
+		get_online_cpus();
 		set_cpus_allowed(current, cpumask_of_cpu(cpu));
 
 		mutex_lock(&microcode_mutex);
 		if (uci->valid)
 			err = cpu_request_microcode(cpu);
 		mutex_unlock(&microcode_mutex);
-		unlock_cpu_hotplug();
+		put_online_cpus();
 		set_cpus_allowed(current, old);
 	}
 	if (err)
@@ -817,9 +817,9 @@ static int __init microcode_init (void)
 		return PTR_ERR(microcode_pdev);
 	}
 
-	lock_cpu_hotplug();
+	get_online_cpus();
 	error = sysdev_driver_register(&cpu_sysdev_class, &mc_sysdev_driver);
-	unlock_cpu_hotplug();
+	put_online_cpus();
 	if (error) {
 		microcode_dev_exit();
 		platform_device_unregister(microcode_pdev);
@@ -839,9 +839,9 @@ static void __exit microcode_exit (void)
 
 	unregister_hotcpu_notifier(&mc_cpu_notifier);
 
-	lock_cpu_hotplug();
+	get_online_cpus();
 	sysdev_driver_unregister(&cpu_sysdev_class, &mc_sysdev_driver);
-	unlock_cpu_hotplug();
+	put_online_cpus();
 
 	platform_device_unregister(microcode_pdev);
 }