Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: VFS: Fix race between CPU hotplug and lglocks

Author: torvalds

include/linux/lglock.h

@@ -22,6 +22,7 @@
 #include <linux/spinlock.h>
 #include <linux/lockdep.h>
 #include <linux/percpu.h>
+#include <linux/cpu.h>
 
 /* can make br locks by using local lock for read side, global lock for write */
 #define br_lock_init(name)	name##_lock_init()
@@ -72,9 +73,31 @@
 
 #define DEFINE_LGLOCK(name)	\
 \
+ DEFINE_SPINLOCK(name##_cpu_lock);	\
+ cpumask_t name##_cpus __read_mostly;	\
  DEFINE_PER_CPU(arch_spinlock_t, name##_lock);	\
  DEFINE_LGLOCK_LOCKDEP(name);	\
 \
+ static int	\
+ name##_lg_cpu_callback(struct notifier_block *nb,	\
+unsigned long action, void *hcpu)	\
+ {	\
+switch (action & ~CPU_TASKS_FROZEN) {	\
+case CPU_UP_PREPARE:	\
+spin_lock(&name##_cpu_lock);	\
+cpu_set((unsigned long)hcpu, name##_cpus);	\
+spin_unlock(&name##_cpu_lock);	\
+break;	\
+case CPU_UP_CANCELED: case CPU_DEAD:	\
+spin_lock(&name##_cpu_lock);	\
+cpu_clear((unsigned long)hcpu, name##_cpus);	\
+spin_unlock(&name##_cpu_lock);	\
+}	\
+return NOTIFY_OK;	\
+ }	\
+ static struct notifier_block name##_lg_cpu_notifier = {	\
+.notifier_call = name##_lg_cpu_callback,	\
+ };	\
  void name##_lock_init(void) {	\
 int i;	\
 LOCKDEP_INIT_MAP(&name##_lock_dep_map, #name, &name##_lock_key, 0); \
@@ -83,6 +106,11 @@
 lock = &per_cpu(name##_lock, i);	\
 *lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;	\
 }	\
+register_hotcpu_notifier(&name##_lg_cpu_notifier);	\
+get_online_cpus();	\
+for_each_online_cpu(i)	\
+cpu_set(i, name##_cpus);	\
+put_online_cpus();	\
  }	\
  EXPORT_SYMBOL(name##_lock_init);	\
 \
@@ -124,9 +152,9 @@
 \
  void name##_global_lock_online(void) {	\
 int i;	\
-preempt_disable();\
+spin_lock(&name##_cpu_lock);\
 rwlock_acquire(&name##_lock_dep_map, 0, 0, _RET_IP_);	\
-for_each_online_cpu(i) {	\
+for_each_cpu(i, &name##_cpus) {	\
 arch_spinlock_t *lock;	\
 lock = &per_cpu(name##_lock, i);	\
 arch_spin_lock(lock);	\
@@ -137,12 +165,12 @@
  void name##_global_unlock_online(void) {	\
 int i;	\
 rwlock_release(&name##_lock_dep_map, 1, _RET_IP_);	\
-for_each_online_cpu(i) {	\
+for_each_cpu(i, &name##_cpus) {	\
 arch_spinlock_t *lock;	\
 lock = &per_cpu(name##_lock, i);	\
 arch_spin_unlock(lock);	\
 }	\
-preempt_enable();\
+spin_unlock(&name##_cpu_lock);\
  }	\
  EXPORT_SYMBOL(name##_global_unlock_online);	\
 \