tracing/probe: Fix to allow user to enable events on unloaded modules

Fix to allow user to enable probe events on unloaded modules.

This operations was allowed before commit 60d53e2c3b75 ("tracing/probe:
Split trace_event related data from trace_probe"), because if users
need to probe module init functions, they have to enable those probe
events before loading module.

Link: http://lkml.kernel.org/r/156879693733.31056.9331322616994665167.stgit@devnote2
Cc: stable@vger.kernel.org
Fixes: 60d53e2c3b75 ("tracing/probe: Split trace_event related data from trace_probe")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 7579c53..0ba3239 100644 (file)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -371,31 +371,24 @@ static int enable_trace_kprobe(struct trace_event_call *call,
        if (enabled)
                return 0;
 
-       enabled = false;
        list_for_each_entry(pos, trace_probe_probe_list(tp), list) {
                tk = container_of(pos, struct trace_kprobe, tp);
                if (trace_kprobe_has_gone(tk))
                        continue;
                ret = __enable_trace_kprobe(tk);
-               if (ret) {
-                       if (enabled) {
-                               __disable_trace_kprobe(tp);
-                               enabled = false;
-                       }
+               if (ret)
                        break;
-               }
                enabled = true;
        }
 
-       if (!enabled) {
-               /* No probe is enabled. Roll back */
+       if (ret) {
+               /* Failed to enable one of them. Roll back all */
+               if (enabled)
+                       __disable_trace_kprobe(tp);
                if (file)
                        trace_probe_remove_file(tp, file);
                else
                        trace_probe_clear_flag(tp, TP_FLAG_PROFILE);
-               if (!ret)
-                       /* Since all probes are gone, this is not available */
-                       ret = -EADDRNOTAVAIL;
        }
 
        return ret;