1 files changed, 266 insertions, 61 deletions

diff --git a/kernel/sys.c b/kernel/sys.c
index 38bc73ede2ba..c93d37f71aef 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -95,99 +95,304 @@ int cad_pid = 1;
  *      and the like. 
  */
 
-static struct notifier_block *reboot_notifier_list;
-static DEFINE_RWLOCK(notifier_lock);
+static BLOCKING_NOTIFIER_HEAD(reboot_notifier_list);
+
+/*
+ *      Notifier chain core routines.  The exported routines below
+ *      are layered on top of these, with appropriate locking added.
+ */
+
+static int notifier_chain_register(struct notifier_block **nl,
+                struct notifier_block *n)
+{
+        while ((*nl) != NULL) {
+                if (n->priority > (*nl)->priority)
+                        break;
+                nl = &((*nl)->next);
+        }
+        n->next = *nl;
+        rcu_assign_pointer(*nl, n);
+        return 0;
+}
+
+static int notifier_chain_unregister(struct notifier_block **nl,
+                struct notifier_block *n)
+{
+        while ((*nl) != NULL) {
+                if ((*nl) == n) {
+                        rcu_assign_pointer(*nl, n->next);
+                        return 0;
+                }
+                nl = &((*nl)->next);
+        }
+        return -ENOENT;
+}
+
+static int __kprobes notifier_call_chain(struct notifier_block **nl,
+                unsigned long val, void *v)
+{
+        int ret = NOTIFY_DONE;
+        struct notifier_block *nb;
+
+        nb = rcu_dereference(*nl);
+        while (nb) {
+                ret = nb->notifier_call(nb, val, v);
+                if ((ret & NOTIFY_STOP_MASK) == NOTIFY_STOP_MASK)
+                        break;
+                nb = rcu_dereference(nb->next);
+        }
+        return ret;
+}
+
+/*
+ *      Atomic notifier chain routines.  Registration and unregistration
+ *      use a mutex, and call_chain is synchronized by RCU (no locks).
+ */
 
 /**
- *      notifier_chain_register - Add notifier to a notifier chain
- *      @list: Pointer to root list pointer
+ *      atomic_notifier_chain_register - Add notifier to an atomic notifier chain
+ *      @nh: Pointer to head of the atomic notifier chain
  *      @n: New entry in notifier chain
  *
- *      Adds a notifier to a notifier chain.
+ *      Adds a notifier to an atomic notifier chain.
  *
  *      Currently always returns zero.
  */
+
+int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
+                struct notifier_block *n)
+{
+        unsigned long flags;
+        int ret;
+
+        spin_lock_irqsave(&nh->lock, flags);
+        ret = notifier_chain_register(&nh->head, n);
+        spin_unlock_irqrestore(&nh->lock, flags);
+        return ret;
+}
+
+EXPORT_SYMBOL_GPL(atomic_notifier_chain_register);
+
+/**
+ *      atomic_notifier_chain_unregister - Remove notifier from an atomic notifier chain
+ *      @nh: Pointer to head of the atomic notifier chain
+ *      @n: Entry to remove from notifier chain
+ *
+ *      Removes a notifier from an atomic notifier chain.
+ *
+ *      Returns zero on success or %-ENOENT on failure.
+ */
+int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
+                struct notifier_block *n)
+{
+        unsigned long flags;
+        int ret;
+
+        spin_lock_irqsave(&nh->lock, flags);
+        ret = notifier_chain_unregister(&nh->head, n);
+        spin_unlock_irqrestore(&nh->lock, flags);
+        synchronize_rcu();
+        return ret;
+}
+
+EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
+
+/**
+ *      atomic_notifier_call_chain - Call functions in an atomic notifier chain
+ *      @nh: Pointer to head of the atomic notifier chain
+ *      @val: Value passed unmodified to notifier function
+ *      @v: Pointer passed unmodified to notifier function
+ *
+ *      Calls each function in a notifier chain in turn.  The functions
+ *      run in an atomic context, so they must not block.
+ *      This routine uses RCU to synchronize with changes to the chain.
+ *
+ *      If the return value of the notifier can be and'ed
+ *      with %NOTIFY_STOP_MASK then atomic_notifier_call_chain
+ *      will return immediately, with the return value of
+ *      the notifier function which halted execution.
+ *      Otherwise the return value is the return value
+ *      of the last notifier function called.
+ */
  
-int notifier_chain_register(struct notifier_block **list, struct notifier_block *n)
+int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
+                unsigned long val, void *v)
 {
-        write_lock(&notifier_lock);
-        while(*list)
-        {
-                if(n->priority > (*list)->priority)
-                        break;
-                list= &((*list)->next);
-        }
-        n->next = *list;
-        *list=n;
-        write_unlock(&notifier_lock);
-        return 0;
+        int ret;
+
+        rcu_read_lock();
+        ret = notifier_call_chain(&nh->head, val, v);
+        rcu_read_unlock();
+        return ret;
 }
 
-EXPORT_SYMBOL(notifier_chain_register);
+EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
+
+/*
+ *      Blocking notifier chain routines.  All access to the chain is
+ *      synchronized by an rwsem.
+ */
 
 /**
- *      notifier_chain_unregister - Remove notifier from a notifier chain
- *      @nl: Pointer to root list pointer
+ *      blocking_notifier_chain_register - Add notifier to a blocking notifier chain
+ *      @nh: Pointer to head of the blocking notifier chain
  *      @n: New entry in notifier chain
  *
- *      Removes a notifier from a notifier chain.
+ *      Adds a notifier to a blocking notifier chain.
+ *      Must be called in process context.
  *
- *      Returns zero on success, or %-ENOENT on failure.
+ *      Currently always returns zero.
  */
  
-int notifier_chain_unregister(struct notifier_block **nl, struct notifier_block *n)
+int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
+                struct notifier_block *n)
 {
-        write_lock(&notifier_lock);
-        while((*nl)!=NULL)
-        {
-                if((*nl)==n)
-                {
-                        *nl=n->next;
-                        write_unlock(&notifier_lock);
-                        return 0;
-                }
-                nl=&((*nl)->next);
-        }
-        write_unlock(&notifier_lock);
-        return -ENOENT;
+        int ret;
+
+        /*
+         * This code gets used during boot-up, when task switching is
+         * not yet working and interrupts must remain disabled.  At
+         * such times we must not call down_write().
+         */
+        if (unlikely(system_state == SYSTEM_BOOTING))
+                return notifier_chain_register(&nh->head, n);
+
+        down_write(&nh->rwsem);
+        ret = notifier_chain_register(&nh->head, n);
+        up_write(&nh->rwsem);
+        return ret;
 }
 
-EXPORT_SYMBOL(notifier_chain_unregister);
+EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
 
 /**
- *      notifier_call_chain - Call functions in a notifier chain
- *      @n: Pointer to root pointer of notifier chain
+ *      blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
+ *      @nh: Pointer to head of the blocking notifier chain
+ *      @n: Entry to remove from notifier chain
+ *
+ *      Removes a notifier from a blocking notifier chain.
+ *      Must be called from process context.
+ *
+ *      Returns zero on success or %-ENOENT on failure.
+ */
+int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
+                struct notifier_block *n)
+{
+        int ret;
+
+        /*
+         * This code gets used during boot-up, when task switching is
+         * not yet working and interrupts must remain disabled.  At
+         * such times we must not call down_write().
+         */
+        if (unlikely(system_state == SYSTEM_BOOTING))
+                return notifier_chain_unregister(&nh->head, n);
+
+        down_write(&nh->rwsem);
+        ret = notifier_chain_unregister(&nh->head, n);
+        up_write(&nh->rwsem);
+        return ret;
+}
+
+EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
+
+/**
+ *      blocking_notifier_call_chain - Call functions in a blocking notifier chain
+ *      @nh: Pointer to head of the blocking notifier chain
  *      @val: Value passed unmodified to notifier function
  *      @v: Pointer passed unmodified to notifier function
  *
- *      Calls each function in a notifier chain in turn.
+ *      Calls each function in a notifier chain in turn.  The functions
+ *      run in a process context, so they are allowed to block.
  *
- *      If the return value of the notifier can be and'd
- *      with %NOTIFY_STOP_MASK, then notifier_call_chain
+ *      If the return value of the notifier can be and'ed
+ *      with %NOTIFY_STOP_MASK then blocking_notifier_call_chain
  *      will return immediately, with the return value of
  *      the notifier function which halted execution.
- *      Otherwise, the return value is the return value
+ *      Otherwise the return value is the return value
  *      of the last notifier function called.
  */
  
-int __kprobes notifier_call_chain(struct notifier_block **n, unsigned long val, void *v)
+int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
+                unsigned long val, void *v)
 {
-        int ret=NOTIFY_DONE;
-        struct notifier_block *nb = *n;
+        int ret;
 
-        while(nb)
-        {
-                ret=nb->notifier_call(nb,val,v);
-                if(ret&NOTIFY_STOP_MASK)
-                {
-                        return ret;
-                }
-                nb=nb->next;
-        }
+        down_read(&nh->rwsem);
+        ret = notifier_call_chain(&nh->head, val, v);
+        up_read(&nh->rwsem);
         return ret;
 }
 
-EXPORT_SYMBOL(notifier_call_chain);
+EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
+
+/*
+ *      Raw notifier chain routines.  There is no protection;
+ *      the caller must provide it.  Use at your own risk!
+ */
+
+/**
+ *      raw_notifier_chain_register - Add notifier to a raw notifier chain
+ *      @nh: Pointer to head of the raw notifier chain
+ *      @n: New entry in notifier chain
+ *
+ *      Adds a notifier to a raw notifier chain.
+ *      All locking must be provided by the caller.
+ *
+ *      Currently always returns zero.
+ */
+
+int raw_notifier_chain_register(struct raw_notifier_head *nh,
+                struct notifier_block *n)
+{
+        return notifier_chain_register(&nh->head, n);
+}
+
+EXPORT_SYMBOL_GPL(raw_notifier_chain_register);
+
+/**
+ *      raw_notifier_chain_unregister - Remove notifier from a raw notifier chain
+ *      @nh: Pointer to head of the raw notifier chain
+ *      @n: Entry to remove from notifier chain
+ *
+ *      Removes a notifier from a raw notifier chain.
+ *      All locking must be provided by the caller.
+ *
+ *      Returns zero on success or %-ENOENT on failure.
+ */
+int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
+                struct notifier_block *n)
+{
+        return notifier_chain_unregister(&nh->head, n);
+}
+
+EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);
+
+/**
+ *      raw_notifier_call_chain - Call functions in a raw notifier chain
+ *      @nh: Pointer to head of the raw notifier chain
+ *      @val: Value passed unmodified to notifier function
+ *      @v: Pointer passed unmodified to notifier function
+ *
+ *      Calls each function in a notifier chain in turn.  The functions
+ *      run in an undefined context.
+ *      All locking must be provided by the caller.
+ *
+ *      If the return value of the notifier can be and'ed
+ *      with %NOTIFY_STOP_MASK then raw_notifier_call_chain
+ *      will return immediately, with the return value of
+ *      the notifier function which halted execution.
+ *      Otherwise the return value is the return value
+ *      of the last notifier function called.
+ */
+
+int raw_notifier_call_chain(struct raw_notifier_head *nh,
+                unsigned long val, void *v)
+{
+        return notifier_call_chain(&nh->head, val, v);
+}
+
+EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
 
 /**
  *      register_reboot_notifier - Register function to be called at reboot time
@@ -196,13 +401,13 @@ EXPORT_SYMBOL(notifier_call_chain);
  *      Registers a function with the list of functions
  *      to be called at reboot time.
  *
- *      Currently always returns zero, as notifier_chain_register
+ *      Currently always returns zero, as blocking_notifier_chain_register
  *      always returns zero.
  */
  
 int register_reboot_notifier(struct notifier_block * nb)
 {
-        return notifier_chain_register(&reboot_notifier_list, nb);
+        return blocking_notifier_chain_register(&reboot_notifier_list, nb);
 }
 
 EXPORT_SYMBOL(register_reboot_notifier);
@@ -219,7 +424,7 @@ EXPORT_SYMBOL(register_reboot_notifier);
  
 int unregister_reboot_notifier(struct notifier_block * nb)
 {
-        return notifier_chain_unregister(&reboot_notifier_list, nb);
+        return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
 }
 
 EXPORT_SYMBOL(unregister_reboot_notifier);
@@ -380,7 +585,7 @@ EXPORT_SYMBOL_GPL(emergency_restart);
 
 void kernel_restart_prepare(char *cmd)
 {
-        notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
+        blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
         system_state = SYSTEM_RESTART;
         device_shutdown();
 }
@@ -430,7 +635,7 @@ EXPORT_SYMBOL_GPL(kernel_kexec);
 
 void kernel_shutdown_prepare(enum system_states state)
 {
-        notifier_call_chain(&reboot_notifier_list,
+        blocking_notifier_call_chain(&reboot_notifier_list,
                 (state == SYSTEM_HALT)?SYS_HALT:SYS_POWER_OFF, NULL);
         system_state = state;
         device_shutdown();