hotplug, powerpc, x86: Remove cpu_hotplug_driver_lock()

cpu_hotplug_driver_lock() serializes CPU online/offline operations
when ARCH_CPU_PROBE_RELEASE is set.  This lock interface is no longer
necessary with the following reason:

 - lock_device_hotplug() now protects CPU online/offline operations,
   including the probe & release interfaces enabled by
   ARCH_CPU_PROBE_RELEASE.  The use of cpu_hotplug_driver_lock() is
   redundant.
 - cpu_hotplug_driver_lock() is only valid when ARCH_CPU_PROBE_RELEASE
   is defined, which is misleading and is only enabled on powerpc.

This patch removes the cpu_hotplug_driver_lock() interface.  As
a result, ARCH_CPU_PROBE_RELEASE only enables / disables the cpu
probe & release interface as intended.  There is no functional change
in this patch.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

5 files changed, 19 insertions, 66 deletions

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 8e59abc237d7..930cd8af3503 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -844,18 +844,6 @@ void __cpu_die(unsigned int cpu)
                 smp_ops->cpu_die(cpu);
 }
 
-static DEFINE_MUTEX(powerpc_cpu_hotplug_driver_mutex);
-
-void cpu_hotplug_driver_lock()
-{
-        mutex_lock(&powerpc_cpu_hotplug_driver_mutex);
-}
-
-void cpu_hotplug_driver_unlock()
-{
-        mutex_unlock(&powerpc_cpu_hotplug_driver_mutex);
-}
-
 void cpu_die(void)
 {
         if (ppc_md.cpu_die)
diff --git a/arch/powerpc/platforms/pseries/dlpar.c b/arch/powerpc/platforms/pseries/dlpar.c
index 7cfdaae1721a..a8fe5aa3d34f 100644
--- a/arch/powerpc/platforms/pseries/dlpar.c
+++ b/arch/powerpc/platforms/pseries/dlpar.c
@@ -404,46 +404,38 @@ static ssize_t dlpar_cpu_probe(const char *buf, size_t count)
         unsigned long drc_index;
         int rc;
 
-        cpu_hotplug_driver_lock();
         rc = strict_strtoul(buf, 0, &drc_index);
-        if (rc) {
-                rc = -EINVAL;
-                goto out;
-        }
+        if (rc)
+                return -EINVAL;
 
         parent = of_find_node_by_path("/cpus");
-        if (!parent) {
-                rc = -ENODEV;
-                goto out;
-        }
+        if (!parent)
+                return -ENODEV;
 
         dn = dlpar_configure_connector(drc_index, parent);
-        if (!dn) {
-                rc = -EINVAL;
-                goto out;
-        }
+        if (!dn)
+                return -EINVAL;
 
         of_node_put(parent);
 
         rc = dlpar_acquire_drc(drc_index);
         if (rc) {
                 dlpar_free_cc_nodes(dn);
-                rc = -EINVAL;
-                goto out;
+                return -EINVAL;
         }
 
         rc = dlpar_attach_node(dn);
         if (rc) {
                 dlpar_release_drc(drc_index);
                 dlpar_free_cc_nodes(dn);
-                goto out;
+                return rc;
         }
 
         rc = dlpar_online_cpu(dn);
-out:
-        cpu_hotplug_driver_unlock();
+        if (rc)
+                return rc;
 
-        return rc ? rc : count;
+        return count;
 }
 
 static int dlpar_offline_cpu(struct device_node *dn)
@@ -516,30 +508,27 @@ static ssize_t dlpar_cpu_release(const char *buf, size_t count)
                 return -EINVAL;
         }
 
-        cpu_hotplug_driver_lock();
         rc = dlpar_offline_cpu(dn);
         if (rc) {
                 of_node_put(dn);
-                rc = -EINVAL;
-                goto out;
+                return -EINVAL;
         }
 
         rc = dlpar_release_drc(*drc_index);
         if (rc) {
                 of_node_put(dn);
-                goto out;
+                return rc;
         }
 
         rc = dlpar_detach_node(dn);
         if (rc) {
                 dlpar_acquire_drc(*drc_index);
-                goto out;
+                return rc;
         }
 
         of_node_put(dn);
-out:
-        cpu_hotplug_driver_unlock();
-        return rc ? rc : count;
+
+        return count;
 }
 
 static int __init pseries_dlpar_init(void)
diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
index a3f35ebb3b52..649b010da00b 100644
--- a/arch/x86/kernel/topology.c
+++ b/arch/x86/kernel/topology.c
@@ -66,7 +66,6 @@ int __ref _debug_hotplug_cpu(int cpu, int action)
                 return -EINVAL;
 
         lock_device_hotplug();
-        cpu_hotplug_driver_lock();
 
         switch (action) {
         case 0:
@@ -91,7 +90,6 @@ int __ref _debug_hotplug_cpu(int cpu, int action)
                 ret = -EINVAL;
         }
 
-        cpu_hotplug_driver_unlock();
         unlock_device_hotplug();
 
         return ret;
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 51f5d7fe2f0b..f48370dfc908 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -44,13 +44,11 @@ static int __ref cpu_subsys_online(struct device *dev)
         struct cpu *cpu = container_of(dev, struct cpu, dev);
         int cpuid = dev->id;
         int from_nid, to_nid;
-        int ret = -ENODEV;
-
-        cpu_hotplug_driver_lock();
+        int ret;
 
         from_nid = cpu_to_node(cpuid);
         if (from_nid == NUMA_NO_NODE)
-                goto out;
+                return -ENODEV;
 
         ret = cpu_up(cpuid);
         /*
@@ -61,19 +59,12 @@ static int __ref cpu_subsys_online(struct device *dev)
         if (from_nid != to_nid)
                 change_cpu_under_node(cpu, from_nid, to_nid);
 
- out:
-        cpu_hotplug_driver_unlock();
         return ret;
 }
 
 static int cpu_subsys_offline(struct device *dev)
 {
-        int ret;
-
-        cpu_hotplug_driver_lock();
-        ret = cpu_down(dev->id);
-        cpu_hotplug_driver_unlock();
-        return ret;
+        return cpu_down(dev->id);
 }
 
 void unregister_cpu(struct cpu *cpu)
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 801ff9e73679..3434ef7de017 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -185,19 +185,6 @@ extern void cpu_hotplug_enable(void);
 void clear_tasks_mm_cpumask(int cpu);
 int cpu_down(unsigned int cpu);
 
-#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
-extern void cpu_hotplug_driver_lock(void);
-extern void cpu_hotplug_driver_unlock(void);
-#else
-static inline void cpu_hotplug_driver_lock(void)
-{
-}
-
-static inline void cpu_hotplug_driver_unlock(void)
-{
-}
-#endif
-
 #else           /* CONFIG_HOTPLUG_CPU */
 
 static inline void cpu_hotplug_begin(void) {}