2.6.25-rc4

 kernel

diff --git a/kernel/marker.c b/kernel/marker.c
index 5323cfa..48a4ea5 100644
--- a/kernel/marker.c
+++ b/kernel/marker.c
@@ -27,35 +27,42 @@
 extern struct marker __start___markers[];
 extern struct marker __stop___markers[];
 
+/* Set to 1 to enable marker debug output */
+const int marker_debug;
+
 /*
  * markers_mutex nests inside module_mutex. Markers mutex protects the builtin
- * and module markers, the hash table and deferred_sync.
+ * and module markers and the hash table.
  */
 static DEFINE_MUTEX(markers_mutex);
 
 /*
- * Marker deferred synchronization.
- * Upon marker probe_unregister, we delay call to synchronize_sched() to
- * accelerate mass unregistration (only when there is no more reference to a
- * given module do we call synchronize_sched()). However, we need to make sure
- * every critical region has ended before we re-arm a marker that has been
- * unregistered and then registered back with a different probe data.
- */
-static int deferred_sync;
-
-/*
  * Marker hash table, containing the active markers.
  * Protected by module_mutex.
  */
 #define MARKER_HASH_BITS 6
 #define MARKER_TABLE_SIZE (1 << MARKER_HASH_BITS)
 
+/*
+ * Note about RCU :
+ * It is used to make sure every handler has finished using its private data
+ * between two consecutive operation (add or remove) on a given marker.  It is
+ * also used to delay the free of multiple probes array until a quiescent state
+ * is reached.
+ * marker entries modifications are protected by the markers_mutex.
+ */
 struct marker_entry {
    struct hlist_node hlist;
    char *format;
-   marker_probe_func *probe;
-   void *private;
+   void (*call)(const struct marker *mdata,   /* Probe wrapper */
+      void *call_private, const char *fmt, ...);
+   struct marker_probe_closure single;
+   struct marker_probe_closure *multi;
    int refcount;   /* Number of times armed. 0 if disarmed. */
+   struct rcu_head rcu;
+   void *oldptr;
+   unsigned char rcu_pending:1;
+   unsigned char ptype:1;
    char name[0];   /* Contains name'\0'format'\0' */
 };
 
@@ -63,7 +70,8 @@ static struct hlist_head marker_table[MARKER_TABLE_SIZE];
 
 /**
  * __mark_empty_function - Empty probe callback
- * @mdata: pointer of type const struct marker
+ * @probe_private: probe private data
+ * @call_private: call site private data
  * @fmt: format string
  * @...: variable argument list
  *
@@ -72,13 +80,267 @@ static struct hlist_head marker_table[MARKER_TABLE_SIZE];
  * though the function pointer change and the marker enabling are two distinct
  * operations that modifies the execution flow of preemptible code.
  */
-void __mark_empty_function(const struct marker *mdata, void *private,
-   const char *fmt, ...)
+void __mark_empty_function(void *probe_private, void *call_private,
+   const char *fmt, va_list *args)
 {
 }
 EXPORT_SYMBOL_GPL(__mark_empty_function);
 
 /*
+ * marker_probe_cb Callback that prepares the variable argument list for probes.
+ * @mdata: pointer of type struct marker
+ * @call_private: caller site private data
+ * @fmt: format string
+ * @...:  Variable argument list.
+ *
+ * Since we do not use "typical" pointer based RCU in the 1 argument case, we
+ * need to put a full smp_rmb() in this branch. This is why we do not use
+ * rcu_dereference() for the pointer read.
+ */
+void marker_probe_cb(const struct marker *mdata, void *call_private,
+   const char *fmt, ...)
+{
+   va_list args;
+   char ptype;
+
+   /*
+    * disabling preemption to make sure the teardown of the callbacks can
+    * be done correctly when they are in modules and they insure RCU read
+    * coherency.
+    */
+   preempt_disable();
+   ptype = ACCESS_ONCE(mdata->ptype);
+   if (likely(!ptype)) {
+      marker_probe_func *func;
+      /* Must read the ptype before ptr. They are not data dependant,
+       * so we put an explicit smp_rmb() here. */
+      smp_rmb();
+      func = ACCESS_ONCE(mdata->single.func);
+      /* Must read the ptr before private data. They are not data
+       * dependant, so we put an explicit smp_rmb() here. */
+      smp_rmb();
+      va_start(args, fmt);
+      func(mdata->single.probe_private, call_private, fmt, &args);
+      va_end(args);
+   } else {
+      struct marker_probe_closure *multi;
+      int i;
+      /*
+       * multi points to an array, therefore accessing the array
+       * depends on reading multi. However, even in this case,
+       * we must insure that the pointer is read _before_ the array
+       * data. Same as rcu_dereference, but we need a full smp_rmb()
+       * in the fast path, so put the explicit barrier here.
+       */
+      smp_read_barrier_depends();
+      multi = ACCESS_ONCE(mdata->multi);
+      for (i = 0; multi[i].func; i++) {
+         va_start(args, fmt);
+         multi[i].func(multi[i].probe_private, call_private, fmt,
+            &args);
+         va_end(args);
+      }
+   }
+   preempt_enable();
+}
+EXPORT_SYMBOL_GPL(marker_probe_cb);
+
+/*
+ * marker_probe_cb Callback that does not prepare the variable argument list.
+ * @mdata: pointer of type struct marker
+ * @call_private: caller site private data
+ * @fmt: format string
+ * @...:  Variable argument list.
+ *
+ * Should be connected to markers "MARK_NOARGS".
+ */
+void marker_probe_cb_noarg(const struct marker *mdata,
+   void *call_private, const char *fmt, ...)
+{
+   va_list args;   /* not initialized */
+   char ptype;
+
+   preempt_disable();
+   ptype = ACCESS_ONCE(mdata->ptype);
+   if (likely(!ptype)) {
+      marker_probe_func *func;
+      /* Must read the ptype before ptr. They are not data dependant,
+       * so we put an explicit smp_rmb() here. */
+      smp_rmb();
+      func = ACCESS_ONCE(mdata->single.func);
+      /* Must read the ptr before private data. They are not data
+       * dependant, so we put an explicit smp_rmb() here. */
+      smp_rmb();
+      func(mdata->single.probe_private, call_private, fmt, &args);
+   } else {
+      struct marker_probe_closure *multi;
+      int i;
+      /*
+       * multi points to an array, therefore accessing the array
+       * depends on reading multi. However, even in this case,
+       * we must insure that the pointer is read _before_ the array
+       * data. Same as rcu_dereference, but we need a full smp_rmb()
+       * in the fast path, so put the explicit barrier here.
+       */
+      smp_read_barrier_depends();
+      multi = ACCESS_ONCE(mdata->multi);
+      for (i = 0; multi[i].func; i++)
+         multi[i].func(multi[i].probe_private, call_private, fmt,
+            &args);
+   }
+   preempt_enable();
+}
+EXPORT_SYMBOL_GPL(marker_probe_cb_noarg);
+
+static void free_old_closure(struct rcu_head *head)
+{
+   struct marker_entry *entry = container_of(head,
+      struct marker_entry, rcu);
+   kfree(entry->oldptr);
+   /* Make sure we free the data before setting the pending flag to 0 */
+   smp_wmb();
+   entry->rcu_pending = 0;
+}
+
+static void debug_print_probes(struct marker_entry *entry)
+{
+   int i;
+
+   if (!marker_debug)
+      return;
+
+   if (!entry->ptype) {
+      printk(KERN_DEBUG "Single probe : %p %p\n",
+         entry->single.func,
+         entry->single.probe_private);
+   } else {
+      for (i = 0; entry->multi[i].func; i++)
+         printk(KERN_DEBUG "Multi probe %d : %p %p\n", i,
+            entry->multi[i].func,
+            entry->multi[i].probe_private);
+   }
+}
+
+static struct marker_probe_closure *
+marker_entry_add_probe(struct marker_entry *entry,
+      marker_probe_func *probe, void *probe_private)
+{
+   int nr_probes = 0;
+   struct marker_probe_closure *old, *new;
+
+   WARN_ON(!probe);
+
+   debug_print_probes(entry);
+   old = entry->multi;
+   if (!entry->ptype) {
+      if (entry->single.func == probe &&
+            entry->single.probe_private == probe_private)
+         return ERR_PTR(-EBUSY);
+      if (entry->single.func == __mark_empty_function) {
+         /* 0 -> 1 probes */
+         entry->single.func = probe;
+         entry->single.probe_private = probe_private;
+         entry->refcount = 1;
+         entry->ptype = 0;
+         debug_print_probes(entry);
+         return NULL;
+      } else {
+         /* 1 -> 2 probes */
+         nr_probes = 1;
+         old = NULL;
+      }
+   } else {
+      /* (N -> N+1), (N != 0, 1) probes */
+      for (nr_probes = 0; old[nr_probes].func; nr_probes++)
+         if (old[nr_probes].func == probe
+               && old[nr_probes].probe_private
+                  == probe_private)
+            return ERR_PTR(-EBUSY);
+   }
+   /* + 2 : one for new probe, one for NULL func */
+   new = kzalloc((nr_probes + 2) * sizeof(struct marker_probe_closure),
+         GFP_KERNEL);
+   if (new == NULL)
+      return ERR_PTR(-ENOMEM);
+   if (!old)
+      new[0] = entry->single;
+   else
+      memcpy(new, old,
+         nr_probes * sizeof(struct marker_probe_closure));
+   new[nr_probes].func = probe;
+   new[nr_probes].probe_private = probe_private;
+   entry->refcount = nr_probes + 1;
+   entry->multi = new;
+   entry->ptype = 1;
+   debug_print_probes(entry);
+   return old;
+}
+
+static struct marker_probe_closure *
+marker_entry_remove_probe(struct marker_entry *entry,
+      marker_probe_func *probe, void *probe_private)
+{
+   int nr_probes = 0, nr_del = 0, i;
+   struct marker_probe_closure *old, *new;
+
+   old = entry->multi;
+
+   debug_print_probes(entry);
+   if (!entry->ptype) {
+      /* 0 -> N is an error */
+      WARN_ON(entry->single.func == __mark_empty_function);
+      /* 1 -> 0 probes */
+      WARN_ON(probe && entry->single.func != probe);
+      WARN_ON(entry->single.probe_private != probe_private);
+      entry->single.func = __mark_empty_function;
+      entry->refcount = 0;
+      entry->ptype = 0;
+      debug_print_probes(entry);
+      return NULL;
+   } else {
+      /* (N -> M), (N > 1, M >= 0) probes */
+      for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
+         if ((!probe || old[nr_probes].func == probe)
+               && old[nr_probes].probe_private
+                  == probe_private)
+            nr_del++;
+      }
+   }
+
+   if (nr_probes - nr_del == 0) {
+      /* N -> 0, (N > 1) */
+      entry->single.func = __mark_empty_function;
+      entry->refcount = 0;
+      entry->ptype = 0;
+   } else if (nr_probes - nr_del == 1) {
+      /* N -> 1, (N > 1) */
+      for (i = 0; old[i].func; i++)
+         if ((probe && old[i].func != probe) ||
+               old[i].probe_private != probe_private)
+            entry->single = old[i];
+      entry->refcount = 1;
+      entry->ptype = 0;
+   } else {
+      int j = 0;
+      /* N -> M, (N > 1, M > 1) */
+      /* + 1 for NULL */
+      new = kzalloc((nr_probes - nr_del + 1)
+         * sizeof(struct marker_probe_closure), GFP_KERNEL);
+      if (new == NULL)
+         return ERR_PTR(-ENOMEM);
+      for (i = 0; old[i].func; i++)
+         if ((probe && old[i].func != probe) ||
+               old[i].probe_private != probe_private)
+            new[j++] = old[i];
+      entry->refcount = nr_probes - nr_del;
+      entry->ptype = 1;
+      entry->multi = new;
+   }
+   debug_print_probes(entry);
+   return old;
+}
+
+/*
  * Get marker if the marker is present in the marker hash table.
  * Must be called with markers_mutex held.
  * Returns NULL if not present.
@@ -102,8 +364,7 @@ static struct marker_entry *get_marker(const char *name)
  * Add the marker to the marker hash table. Must be called with markers_mutex
  * held.
  */
-static int add_marker(const char *name, const char *format,
-   marker_probe_func *probe, void *private)
+static struct marker_entry *add_marker(const char *name, const char *format)
 {
    struct hlist_head *head;
    struct hlist_node *node;
@@ -118,9 +379,8 @@ static int add_marker(const char *name, const char *format,
    hlist_for_each_entry(e, node, head, hlist) {
       if (!strcmp(name, e->name)) {
          printk(KERN_NOTICE
-            "Marker %s busy, probe %p already installed\n",
-            name, e->probe);
-         return -EBUSY;   /* Already there */
+            "Marker %s busy\n", name);
+         return ERR_PTR(-EBUSY);   /* Already there */
       }
    }
    /*
@@ -130,34 +390,42 @@ static int add_marker(const char *name, const char *format,
    e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
          GFP_KERNEL);
    if (!e)
-      return -ENOMEM;
+      return ERR_PTR(-ENOMEM);
    memcpy(&e->name[0], name, name_len);
    if (format) {
       e->format = &e->name[name_len];
       memcpy(e->format, format, format_len);
+      if (strcmp(e->format, MARK_NOARGS) == 0)
+         e->call = marker_probe_cb_noarg;
+      else
+         e->call = marker_probe_cb;
       trace_mark(core_marker_format, "name %s format %s",
             e->name, e->format);
-   } else
+   } else {
       e->format = NULL;
-   e->probe = probe;
-   e->private = private;
+      e->call = marker_probe_cb;
+   }
+   e->single.func = __mark_empty_function;
+   e->single.probe_private = NULL;
+   e->multi = NULL;
+   e->ptype = 0;
    e->refcount = 0;
+   e->rcu_pending = 0;
    hlist_add_head(&e->hlist, head);
-   return 0;
+   return e;
 }
 
 /*
  * Remove the marker from the marker hash table. Must be called with mutex_lock
  * held.
  */
-static void *remove_marker(const char *name)
+static int remove_marker(const char *name)
 {
    struct hlist_head *head;
    struct hlist_node *node;
    struct marker_entry *e;
    int found = 0;
    size_t len = strlen(name) + 1;
-   void *private = NULL;
    u32 hash = jhash(name, len-1, 0);
 
    head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
@@ -167,12 +435,16 @@ static void *remove_marker(const char *name)
          break;
       }
    }
-   if (found) {
-      private = e->private;
-      hlist_del(&e->hlist);
-      kfree(e);
-   }
-   return private;
+   if (!found)
+      return -ENOENT;
+   if (e->single.func != __mark_empty_function)
+      return -EBUSY;
+   hlist_del(&e->hlist);
+   /* Make sure the call_rcu has been executed */
+   if (e->rcu_pending)
+      rcu_barrier();
+   kfree(e);
+   return 0;
 }
 
 /*
@@ -184,6 +456,7 @@ static int marker_set_format(struct marker_entry **entry, const char *format)
    size_t name_len = strlen((*entry)->name) + 1;
    size_t format_len = strlen(format) + 1;
 
+
    e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
          GFP_KERNEL);
    if (!e)
@@ -191,11 +464,20 @@ static int marker_set_format(struct marker_entry **entry, const char *format)
    memcpy(&e->name[0], (*entry)->name, name_len);
    e->format = &e->name[name_len];
    memcpy(e->format, format, format_len);
-   e->probe = (*entry)->probe;
-   e->private = (*entry)->private;
+   if (strcmp(e->format, MARK_NOARGS) == 0)
+      e->call = marker_probe_cb_noarg;
+   else
+      e->call = marker_probe_cb;
+   e->single = (*entry)->single;
+   e->multi = (*entry)->multi;
+   e->ptype = (*entry)->ptype;
    e->refcount = (*entry)->refcount;
+   e->rcu_pending = 0;
    hlist_add_before(&e->hlist, &(*entry)->hlist);
    hlist_del(&(*entry)->hlist);
+   /* Make sure the call_rcu has been executed */
+   if ((*entry)->rcu_pending)
+      rcu_barrier();
    kfree(*entry);
    *entry = e;
    trace_mark(core_marker_format, "name %s format %s",
@@ -206,7 +488,8 @@ static int marker_set_format(struct marker_entry **entry, const char *format)
 /*
  * Sets the probe callback corresponding to one marker.
  */
-static int set_marker(struct marker_entry **entry, struct marker *elem)
+static int set_marker(struct marker_entry **entry, struct marker *elem,
+      int active)
 {
    int ret;
    WARN_ON(strcmp((*entry)->name, elem->name) != 0);
@@ -226,9 +509,43 @@ static int set_marker(struct marker_entry **entry, struct marker *elem)
       if (ret)
          return ret;
    }
-   elem->call = (*entry)->probe;
-   elem->private = (*entry)->private;
-   elem->state = 1;
+
+   /*
+    * probe_cb setup (statically known) is done here. It is
+    * asynchronous with the rest of execution, therefore we only
+    * pass from a "safe" callback (with argument) to an "unsafe"
+    * callback (does not set arguments).
+    */
+   elem->call = (*entry)->call;
+   /*
+    * Sanity check :
+    * We only update the single probe private data when the ptr is
+    * set to a _non_ single probe! (0 -> 1 and N -> 1, N != 1)
+    */
+   WARN_ON(elem->single.func != __mark_empty_function
+      && elem->single.probe_private
+      != (*entry)->single.probe_private &&
+      !elem->ptype);
+   elem->single.probe_private = (*entry)->single.probe_private;
+   /*
+    * Make sure the private data is valid when we update the
+    * single probe ptr.
+    */
+   smp_wmb();
+   elem->single.func = (*entry)->single.func;
+   /*
+    * We also make sure that the new probe callbacks array is consistent
+    * before setting a pointer to it.
+    */
+   rcu_assign_pointer(elem->multi, (*entry)->multi);
+   /*
+    * Update the function or multi probe array pointer before setting the
+    * ptype.
+    */
+   smp_wmb();
+   elem->ptype = (*entry)->ptype;
+   elem->state = active;
+
    return 0;
 }
 
@@ -240,8 +557,12 @@ static int set_marker(struct marker_entry **entry, struct marker *elem)
  */
 static void disable_marker(struct marker *elem)
 {
+   /* leave "call" as is. It is known statically. */
    elem->state = 0;
-   elem->call = __mark_empty_function;
+   elem->single.func = __mark_empty_function;
+   /* Update the function before setting the ptype */
+   smp_wmb();
+   elem->ptype = 0;   /* single probe */
    /*
     * Leave the private data and id there, because removal is racy and
     * should be done only after a synchronize_sched(). These are never used
@@ -253,14 +574,11 @@ static void disable_marker(struct marker *elem)
  * marker_update_probe_range - Update a probe range
  * @begin: beginning of the range
  * @end: end of the range
- * @probe_module: module address of the probe being updated
- * @refcount: number of references left to the given probe_module (out)
  *
  * Updates the probe callback corresponding to a range of markers.
  */
 void marker_update_probe_range(struct marker *begin,
-   struct marker *end, struct module *probe_module,
-   int *refcount)
+   struct marker *end)
 {
    struct marker *iter;
    struct marker_entry *mark_entry;
@@ -268,15 +586,12 @@ void marker_update_probe_range(struct marker *begin,
    mutex_lock(&markers_mutex);
    for (iter = begin; iter < end; iter++) {
       mark_entry = get_marker(iter->name);
-      if (mark_entry && mark_entry->refcount) {
-         set_marker(&mark_entry, iter);
+      if (mark_entry) {
+         set_marker(&mark_entry, iter,
+               !!mark_entry->refcount);
          /*
           * ignore error, continue
           */
-         if (probe_module)
-            if (probe_module ==
-         __module_text_address((unsigned long)mark_entry->probe))
-               (*refcount)++;
       } else {
          disable_marker(iter);
       }
@@ -289,20 +604,27 @@ void marker_update_probe_range(struct marker *begin,
  * Issues a synchronize_sched() when no reference to the module passed
  * as parameter is found in the probes so the probe module can be
  * safely unloaded from now on.
+ *
+ * Internal callback only changed before the first probe is connected to it.
+ * Single probe private data can only be changed on 0 -> 1 and 2 -> 1
+ * transitions.  All other transitions will leave the old private data valid.
+ * This makes the non-atomicity of the callback/private data updates valid.
+ *
+ * "special case" updates :
+ * 0 -> 1 callback
+ * 1 -> 0 callback
+ * 1 -> 2 callbacks
+ * 2 -> 1 callbacks
+ * Other updates all behave the same, just like the 2 -> 3 or 3 -> 2 updates.
+ * Site effect : marker_set_format may delete the marker entry (creating a
+ * replacement).
  */
-static void marker_update_probes(struct module *probe_module)
+static void marker_update_probes(void)
 {
-   int refcount = 0;
-
    /* Core kernel markers */
-   marker_update_probe_range(__start___markers,
-         __stop___markers, probe_module, &refcount);
+   marker_update_probe_range(__start___markers, __stop___markers);
    /* Markers in modules. */
-   module_update_markers(probe_module, &refcount);
-   if (probe_module && refcount == 0) {
-      synchronize_sched();
-      deferred_sync = 0;
-   }
+   module_update_markers();
 }
 
 /**
@@ -310,33 +632,49 @@ static void marker_update_probes(struct module *probe_module)
  * @name: marker name
  * @format: format string
  * @probe: probe handler
- * @private: probe private data
+ * @probe_private: probe private data
  *
  * private data must be a valid allocated memory address, or NULL.
  * Returns 0 if ok, error value on error.
+ * The probe address must at least be aligned on the architecture pointer size.
  */
 int marker_probe_register(const char *name, const char *format,
-         marker_probe_func *probe, void *private)
+         marker_probe_func *probe, void *probe_private)
 {
    struct marker_entry *entry;
    int ret = 0;
+   struct marker_probe_closure *old;
 
    mutex_lock(&markers_mutex);
    entry = get_marker(name);
-   if (entry && entry->refcount) {
-      ret = -EBUSY;
-      goto end;
-   }
-   if (deferred_sync) {
-      synchronize_sched();
-      deferred_sync = 0;
+   if (!entry) {
+      entry = add_marker(name, format);
+      if (IS_ERR(entry)) {
+         ret = PTR_ERR(entry);
+         goto end;
+      }
    }
-   ret = add_marker(name, format, probe, private);
-   if (ret)
+   /*
+    * If we detect that a call_rcu is pending for this marker,
+    * make sure it's executed now.
+    */
+   if (entry->rcu_pending)
+      rcu_barrier();
+   old = marker_entry_add_probe(entry, probe, probe_private);
+   if (IS_ERR(old)) {
+      ret = PTR_ERR(old);
       goto end;
+   }
    mutex_unlock(&markers_mutex);
-   marker_update_probes(NULL);
-   return ret;
+   marker_update_probes();      /* may update entry */
+   mutex_lock(&markers_mutex);
+   entry = get_marker(name);
+   WARN_ON(!entry);
+   entry->oldptr = old;
+   entry->rcu_pending = 1;
+   /* write rcu_pending before calling the RCU callback */
+   smp_wmb();
+   call_rcu(&entry->rcu, free_old_closure);
 end:
    mutex_unlock(&markers_mutex);
    return ret;
@@ -346,171 +684,167 @@ EXPORT_SYMBOL_GPL(marker_probe_register);
 /**
  * marker_probe_unregister -  Disconnect a probe from a marker
  * @name: marker name
+ * @probe: probe function pointer
+ * @probe_private: probe private data
  *
  * Returns the private data given to marker_probe_register, or an ERR_PTR().
+ * We do not need to call a synchronize_sched to make sure the probes have
+ * finished running before doing a module unload, because the module unload
+ * itself uses stop_machine(), which insures that every preempt disabled section
+ * have finished.
  */
-void *marker_probe_unregister(const char *name)
+int marker_probe_unregister(const char *name,
+   marker_probe_func *probe, void *probe_private)
 {
-   struct module *probe_module;
    struct marker_entry *entry;
-   void *private;
+   struct marker_probe_closure *old;
+   int ret = -ENOENT;
 
    mutex_lock(&markers_mutex);
    entry = get_marker(name);
-   if (!entry) {
-      private = ERR_PTR(-ENOENT);
+   if (!entry)
       goto end;
-   }
-   entry->refcount = 0;
-   /* In what module is the probe handler ? */
-   probe_module = __module_text_address((unsigned long)entry->probe);
-   private = remove_marker(name);
-   deferred_sync = 1;
+   if (entry->rcu_pending)
+      rcu_barrier();
+   old = marker_entry_remove_probe(entry, probe, probe_private);
    mutex_unlock(&markers_mutex);
-   marker_update_probes(probe_module);
-   return private;
+   marker_update_probes();      /* may update entry */
+   mutex_lock(&markers_mutex);
+   entry = get_marker(name);
+   if (!entry)
+      goto end;
+   entry->oldptr = old;
+   entry->rcu_pending = 1;
+   /* write rcu_pending before calling the RCU callback */
+   smp_wmb();
+   call_rcu(&entry->rcu, free_old_closure);
+   remove_marker(name);   /* Ignore busy error message */
+   ret = 0;
 end:
    mutex_unlock(&markers_mutex);
-   return private;
+   return ret;
 }
 EXPORT_SYMBOL_GPL(marker_probe_unregister);
 
-/**
- * marker_probe_unregister_private_data -  Disconnect a probe from a marker
- * @private: probe private data
- *
- * Unregister a marker by providing the registered private data.
- * Returns the private data given to marker_probe_register, or an ERR_PTR().
- */
-void *marker_probe_unregister_private_data(void *private)
+static struct marker_entry *
+get_marker_from_private_data(marker_probe_func *probe, void *probe_private)
 {
-   struct module *probe_module;
-   struct hlist_head *head;
-   struct hlist_node *node;
    struct marker_entry *entry;
-   int found = 0;
    unsigned int i;
+   struct hlist_head *head;
+   struct hlist_node *node;
 
-   mutex_lock(&markers_mutex);
    for (i = 0; i < MARKER_TABLE_SIZE; i++) {
       head = &marker_table[i];
       hlist_for_each_entry(entry, node, head, hlist) {
-         if (entry->private == private) {
-            found = 1;
-            goto iter_end;
+         if (!entry->ptype) {
+            if (entry->single.func == probe
+                  && entry->single.probe_private
+                  == probe_private)
+               return entry;
+         } else {
+            struct marker_probe_closure *closure;
+            closure = entry->multi;
+            for (i = 0; closure[i].func; i++) {
+               if (closure[i].func == probe &&
+                     closure[i].probe_private
+                     == probe_private)
+                  return entry;
+            }
          }
       }
    }
-iter_end:
-   if (!found) {
-      private = ERR_PTR(-ENOENT);
-      goto end;
-   }
-   entry->refcount = 0;
-   /* In what module is the probe handler ? */
-   probe_module = __module_text_address((unsigned long)entry->probe);
-   private = remove_marker(entry->name);
-   deferred_sync = 1;
-   mutex_unlock(&markers_mutex);
-   marker_update_probes(probe_module);
-   return private;
-end:
-   mutex_unlock(&markers_mutex);
-   return private;
+   return NULL;
 }
-EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
 
 /**
- * marker_arm - Arm a marker
- * @name: marker name
+ * marker_probe_unregister_private_data -  Disconnect a probe from a marker
+ * @probe: probe function
+ * @probe_private: probe private data
  *
- * Activate a marker. It keeps a reference count of the number of
- * arming/disarming done.
- * Returns 0 if ok, error value on error.
+ * Unregister a probe by providing the registered private data.
+ * Only removes the first marker found in hash table.
+ * Return 0 on success or error value.
+ * We do not need to call a synchronize_sched to make sure the probes have
+ * finished running before doing a module unload, because the module unload
+ * itself uses stop_machine(), which insures that every preempt disabled section
+ * have finished.
  */
-int marker_arm(const char *name)
+int marker_probe_unregister_private_data(marker_probe_func *probe,
+      void *probe_private)
 {
    struct marker_entry *entry;
    int ret = 0;
+   struct marker_probe_closure *old;
 
    mutex_lock(&markers_mutex);
-   entry = get_marker(name);
+   entry = get_marker_from_private_data(probe, probe_private);
    if (!entry) {
       ret = -ENOENT;
       goto end;
    }
-   /*
-    * Only need to update probes when refcount passes from 0 to 1.
-    */
-   if (entry->refcount++)
-      goto end;
-end:
+   if (entry->rcu_pending)
+      rcu_barrier();
+   old = marker_entry_remove_probe(entry, NULL, probe_private);
    mutex_unlock(&markers_mutex);
-   marker_update_probes(NULL);
-   return ret;
-}
-EXPORT_SYMBOL_GPL(marker_arm);
-
-/**
- * marker_disarm - Disarm a marker
- * @name: marker name
- *
- * Disarm a marker. It keeps a reference count of the number of arming/disarming
- * done.
- * Returns 0 if ok, error value on error.
- */
-int marker_disarm(const char *name)
-{
-   struct marker_entry *entry;
-   int ret = 0;
-
+   marker_update_probes();      /* may update entry */
    mutex_lock(&markers_mutex);
-   entry = get_marker(name);
-   if (!entry) {
-      ret = -ENOENT;
-      goto end;
-   }
-   /*
-    * Only permit decrement refcount if higher than 0.
-    * Do probe update only on 1 -> 0 transition.
-    */
-   if (entry->refcount) {
-      if (--entry->refcount)
-         goto end;
-   } else {
-      ret = -EPERM;
-      goto end;
-   }
+   entry = get_marker_from_private_data(probe, probe_private);
+   WARN_ON(!entry);
+   entry->oldptr = old;
+   entry->rcu_pending = 1;
+   /* write rcu_pending before calling the RCU callback */
+   smp_wmb();
+   call_rcu(&entry->rcu, free_old_closure);
+   remove_marker(entry->name);   /* Ignore busy error message */
 end:
    mutex_unlock(&markers_mutex);
-   marker_update_probes(NULL);
    return ret;
 }
-EXPORT_SYMBOL_GPL(marker_disarm);
+EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
 
 /**
  * marker_get_private_data - Get a marker's probe private data
  * @name: marker name
+ * @probe: probe to match
+ * @num: get the nth matching probe's private data
  *
+ * Returns the nth private data pointer (starting from 0) matching, or an
+ * ERR_PTR.
  * Returns the private data pointer, or an ERR_PTR.
  * The private data pointer should _only_ be dereferenced if the caller is the
  * owner of the data, or its content could vanish. This is mostly used to
  * confirm that a caller is the owner of a registered probe.
  */
-void *marker_get_private_data(const char *name)
+void *marker_get_private_data(const char *name, marker_probe_func *probe,
+      int num)
 {
    struct hlist_head *head;
    struct hlist_node *node;
    struct marker_entry *e;
    size_t name_len = strlen(name) + 1;
    u32 hash = jhash(name, name_len-1, 0);
-   int found = 0;
+   int i;
 
    head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
    hlist_for_each_entry(e, node, head, hlist) {
       if (!strcmp(name, e->name)) {
-         found = 1;
-         return e->private;
+         if (!e->ptype) {
+            if (num == 0 && e->single.func == probe)
+               return e->single.probe_private;
+            else
+               break;
+         } else {
+            struct marker_probe_closure *closure;
+            int match = 0;
+            closure = e->multi;
+            for (i = 0; closure[i].func; i++) {
+               if (closure[i].func != probe)
+                  continue;
+               if (match++ == num)
+                  return closure[i].probe_private;
+            }
+         }
       }
    }
    return ERR_PTR(-ENOENT);