Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/bp/bp

[~andy/linux] / kernel / tracepoint.c

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index be86b9a01a095125c060d41af0d4ee4be4c057b6..9489a0a9b1be69ed21234d9211df1f05a9857ec5 100644 (file)
--- 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);
 }
@@ -576,9 +584,9 @@ __initcall(init_tracepoints);
 
 #endif /* CONFIG_MODULES */
 
-#ifdef CONFIG_FTRACE_SYSCALLS
+#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)
@@ -586,16 +594,16 @@ 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) {
-                       set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
+                       /* 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++;
-       mutex_unlock(&regfunc_mutex);
 }
 
 void syscall_unregfunc(void)
@@ -603,7 +611,6 @@ 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 +619,5 @@ void syscall_unregfunc(void)
                } while_each_thread(g, t);
                read_unlock_irqrestore(&tasklist_lock, flags);
        }
-       mutex_unlock(&regfunc_mutex);
 }
 #endif