1 files changed, 47 insertions, 3 deletions

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 1ef5d3a601c7..9489a0a9b1be 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -24,6 +24,7 @@
 #include <linux/tracepoint.h>
 #include <linux/err.h>
 #include <linux/slab.h>
+#include <linux/sched.h>
 
 extern struct tracepoint __start___tracepoints[];
 extern struct tracepoint __stop___tracepoints[];
@@ -242,6 +243,11 @@ static void set_tracepoint(struct tracepoint_entry **entry,
 {
         WARN_ON(strcmp((*entry)->name, elem->name) != 0);
 
+        if (elem->regfunc && !elem->state && active)
+                elem->regfunc();
+        else if (elem->unregfunc && elem->state && !active)
+                elem->unregfunc();
+
         /*
          * rcu_assign_pointer has a smp_wmb() which makes sure that the new
          * probe callbacks array is consistent before setting a pointer to it.
@@ -261,6 +267,9 @@ static void set_tracepoint(struct tracepoint_entry **entry,
  */
 static void disable_tracepoint(struct tracepoint *elem)
 {
+        if (elem->unregfunc && elem->state)
+                elem->unregfunc();
+
         elem->state = 0;
         rcu_assign_pointer(elem->funcs, NULL);
 }
@@ -554,9 +563,6 @@ int tracepoint_module_notify(struct notifier_block *self,
 
         switch (val) {
         case MODULE_STATE_COMING:
-                tracepoint_update_probe_range(mod->tracepoints,
-                        mod->tracepoints + mod->num_tracepoints);
-                break;
         case MODULE_STATE_GOING:
                 tracepoint_update_probe_range(mod->tracepoints,
                         mod->tracepoints + mod->num_tracepoints);
@@ -577,3 +583,41 @@ static int init_tracepoints(void)
 __initcall(init_tracepoints);
 
 #endif /* CONFIG_MODULES */
+
+#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
+
+/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
+static int sys_tracepoint_refcount;
+
+void syscall_regfunc(void)
+{
+        unsigned long flags;
+        struct task_struct *g, *t;
+
+        if (!sys_tracepoint_refcount) {
+                read_lock_irqsave(&tasklist_lock, flags);
+                do_each_thread(g, t) {
+                        /* Skip kernel threads. */
+                        if (t->mm)
+                                set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
+                } while_each_thread(g, t);
+                read_unlock_irqrestore(&tasklist_lock, flags);
+        }
+        sys_tracepoint_refcount++;
+}
+
+void syscall_unregfunc(void)
+{
+        unsigned long flags;
+        struct task_struct *g, *t;
+
+        sys_tracepoint_refcount--;
+        if (!sys_tracepoint_refcount) {
+                read_lock_irqsave(&tasklist_lock, flags);
+                do_each_thread(g, t) {
+                        clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
+                } while_each_thread(g, t);
+                read_unlock_irqrestore(&tasklist_lock, flags);
+        }
+}
+#endif