1 files changed, 23 insertions, 17 deletions

diff --git a/kernel/marker.c b/kernel/marker.c
index 48a4ea5afffd..005b95954593 100644
--- a/kernel/marker.c
+++ b/kernel/marker.c
@@ -104,18 +104,18 @@ void marker_probe_cb(const struct marker *mdata, void *call_private,
         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 does two things : 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);
+        ptype = 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);
+                func = 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();
@@ -133,7 +133,7 @@ void marker_probe_cb(const struct marker *mdata, void *call_private,
                  * in the fast path, so put the explicit barrier here.
                  */
                 smp_read_barrier_depends();
-                multi = ACCESS_ONCE(mdata->multi);
+                multi = mdata->multi;
                 for (i = 0; multi[i].func; i++) {
                         va_start(args, fmt);
                         multi[i].func(multi[i].probe_private, call_private, fmt,
@@ -161,13 +161,13 @@ void marker_probe_cb_noarg(const struct marker *mdata,
         char ptype;
 
         preempt_disable();
-        ptype = ACCESS_ONCE(mdata->ptype);
+        ptype = 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);
+                func = 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();
@@ -183,7 +183,7 @@ void marker_probe_cb_noarg(const struct marker *mdata,
                  * in the fast path, so put the explicit barrier here.
                  */
                 smp_read_barrier_depends();
-                multi = ACCESS_ONCE(mdata->multi);
+                multi = mdata->multi;
                 for (i = 0; multi[i].func; i++)
                         multi[i].func(multi[i].probe_private, call_private, fmt,
                                 &args);
@@ -551,9 +551,9 @@ static int set_marker(struct marker_entry **entry, struct marker *elem,
 
 /*
  * Disable a marker and its probe callback.
- * Note: only after a synchronize_sched() issued after setting elem->call to the
- * empty function insures that the original callback is not used anymore. This
- * insured by preemption disabling around the call site.
+ * Note: only waiting an RCU period after setting elem->call to the empty
+ * function insures that the original callback is not used anymore. This insured
+ * by preempt_disable around the call site.
  */
 static void disable_marker(struct marker *elem)
 {
@@ -565,8 +565,8 @@ static void disable_marker(struct marker *elem)
         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
-         * until the next initialization anyway.
+         * should be done only after an RCU period. These are never used until
+         * the next initialization anyway.
          */
 }
 
@@ -601,9 +601,6 @@ void marker_update_probe_range(struct marker *begin,
 
 /*
  * Update probes, removing the faulty probes.
- * 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
@@ -674,6 +671,9 @@ int marker_probe_register(const char *name, const char *format,
         entry->rcu_pending = 1;
         /* write rcu_pending before calling the RCU callback */
         smp_wmb();
+#ifdef CONFIG_PREEMPT_RCU
+        synchronize_sched();    /* Until we have the call_rcu_sched() */
+#endif
         call_rcu(&entry->rcu, free_old_closure);
 end:
         mutex_unlock(&markers_mutex);
@@ -717,6 +717,9 @@ int marker_probe_unregister(const char *name,
         entry->rcu_pending = 1;
         /* write rcu_pending before calling the RCU callback */
         smp_wmb();
+#ifdef CONFIG_PREEMPT_RCU
+        synchronize_sched();    /* Until we have the call_rcu_sched() */
+#endif
         call_rcu(&entry->rcu, free_old_closure);
         remove_marker(name);    /* Ignore busy error message */
         ret = 0;
@@ -795,6 +798,9 @@ int marker_probe_unregister_private_data(marker_probe_func *probe,
         entry->rcu_pending = 1;
         /* write rcu_pending before calling the RCU callback */
         smp_wmb();
+#ifdef CONFIG_PREEMPT_RCU
+        synchronize_sched();    /* Until we have the call_rcu_sched() */
+#endif
         call_rcu(&entry->rcu, free_old_closure);
         remove_marker(entry->name);     /* Ignore busy error message */
 end: