3 files changed, 19 insertions, 6 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index b0f239e443bc..1e3fd3e3436a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -545,6 +545,16 @@ config DEBUG_SG
 
           If unsure, say N.
 
+config DEBUG_NOTIFIERS
+        bool "Debug notifier call chains"
+        depends on DEBUG_KERNEL
+        help
+          Enable this to turn on sanity checking for notifier call chains.
+          This is most useful for kernel developers to make sure that
+          modules properly unregister themselves from notifier chains.
+          This is a relatively cheap check but if you care about maximum
+          performance, say N.
+
 config FRAME_POINTER
         bool "Compile the kernel with frame pointers"
         depends on DEBUG_KERNEL && \
diff --git a/lib/idr.c b/lib/idr.c
index 7a785a0c2ea0..1c4f9281f412 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -220,8 +220,14 @@ build_up:
          */
         while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
                 layers++;
-                if (!p->count)
+                if (!p->count) {
+                        /* special case: if the tree is currently empty,
+                         * then we grow the tree by moving the top node
+                         * upwards.
+                         */
+                        p->layer++;
                         continue;
+                }
                 if (!(new = get_from_free_list(idp))) {
                         /*
                          * The allocation failed.  If we built part of
diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
index a8663890a88c..b255b939bc1b 100644
--- a/lib/percpu_counter.c
+++ b/lib/percpu_counter.c
@@ -62,10 +62,7 @@ s64 __percpu_counter_sum(struct percpu_counter *fbc)
         for_each_online_cpu(cpu) {
                 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
                 ret += *pcount;
-                *pcount = 0;
         }
-        fbc->count = ret;
-
         spin_unlock(&fbc->lock);
         return ret;
 }
@@ -104,13 +101,13 @@ void percpu_counter_destroy(struct percpu_counter *fbc)
         if (!fbc->counters)
                 return;
 
-        free_percpu(fbc->counters);
-        fbc->counters = NULL;
 #ifdef CONFIG_HOTPLUG_CPU
         mutex_lock(&percpu_counters_lock);
         list_del(&fbc->list);
         mutex_unlock(&percpu_counters_lock);
 #endif
+        free_percpu(fbc->counters);
+        fbc->counters = NULL;
 }
 EXPORT_SYMBOL(percpu_counter_destroy);