1 files changed, 9 insertions, 5 deletions

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 9e0a36f0e2a9..1a6a453b7efb 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -243,6 +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.
@@ -262,6 +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);
 }
@@ -578,7 +586,7 @@ __initcall(init_tracepoints);
 
 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
 
-static DEFINE_MUTEX(regfunc_mutex);
+/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
 static int sys_tracepoint_refcount;
 
 void syscall_regfunc(void)
@@ -586,7 +594,6 @@ void syscall_regfunc(void)
         unsigned long flags;
         struct task_struct *g, *t;
 
-        mutex_lock(&regfunc_mutex);
         if (!sys_tracepoint_refcount) {
                 read_lock_irqsave(&tasklist_lock, flags);
                 do_each_thread(g, t) {
@@ -595,7 +602,6 @@ void syscall_regfunc(void)
                 read_unlock_irqrestore(&tasklist_lock, flags);
         }
         sys_tracepoint_refcount++;
-        mutex_unlock(&regfunc_mutex);
 }
 
 void syscall_unregfunc(void)
@@ -603,7 +609,6 @@ void syscall_unregfunc(void)
         unsigned long flags;
         struct task_struct *g, *t;
 
-        mutex_lock(&regfunc_mutex);
         sys_tracepoint_refcount--;
         if (!sys_tracepoint_refcount) {
                 read_lock_irqsave(&tasklist_lock, flags);
@@ -612,6 +617,5 @@ void syscall_unregfunc(void)
                 } while_each_thread(g, t);
                 read_unlock_irqrestore(&tasklist_lock, flags);
         }
-        mutex_unlock(&regfunc_mutex);
 }
 #endif