tracing: Have the reg function allow to fail

Some tracepoints have a registration function that gets enabled when the
tracepoint is enabled. There may be cases that the registraction function
must fail (for example, can't allocate enough memory). In this case, the
tracepoint should also fail to register, otherwise the user would not know
why the tracepoint is not working.

Cc: David Howells <dhowells@redhat.com>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 9 insertions, 3 deletions

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index d0639d917899..1f9a31f934a4 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -194,9 +194,13 @@ static int tracepoint_add_func(struct tracepoint *tp,
                                struct tracepoint_func *func, int prio)
 {
         struct tracepoint_func *old, *tp_funcs;
+        int ret;
 
-        if (tp->regfunc && !static_key_enabled(&tp->key))
-                tp->regfunc();
+        if (tp->regfunc && !static_key_enabled(&tp->key)) {
+                ret = tp->regfunc();
+                if (ret < 0)
+                        return ret;
+        }
 
         tp_funcs = rcu_dereference_protected(tp->funcs,
                         lockdep_is_held(&tracepoints_mutex));
@@ -529,7 +533,7 @@ EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
 static int sys_tracepoint_refcount;
 
-void syscall_regfunc(void)
+int syscall_regfunc(void)
 {
         struct task_struct *p, *t;
 
@@ -541,6 +545,8 @@ void syscall_regfunc(void)
                 read_unlock(&tasklist_lock);
         }
         sys_tracepoint_refcount++;
+
+        return 0;
 }
 
 void syscall_unregfunc(void)