tracing: Switch trace_events_filter.c code over to use guard()

There are a couple functions in trace_events_filter.c that have "goto out"
or equivalent on error in order to release locks that were taken. This can
be error prone or just simply make the code more complex.

Switch every location that ends with unlocking a mutex on error over to
using the guard(mutex)() infrastructure to let the compiler worry about
releasing locks. This makes the code easier to read and understand.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/20241219201346.200737679@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 78051de581e78536bba3d11eb06004fd9ba44ab9..0993dfc1c5c165d5f07ddb442ac66bb22f54f2ea 100644 (file)
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -2405,13 +2405,11 @@ int apply_subsystem_event_filter(struct trace_subsystem_dir *dir,
        struct event_filter *filter = NULL;
        int err = 0;
 
-       mutex_lock(&event_mutex);
+       guard(mutex)(&event_mutex);
 
        /* Make sure the system still has events */
-       if (!dir->nr_events) {
-               err = -ENODEV;
-               goto out_unlock;
-       }
+       if (!dir->nr_events)
+               return -ENODEV;
 
        if (!strcmp(strstrip(filter_string), "0")) {
                filter_free_subsystem_preds(dir, tr);
@@ -2422,7 +2420,7 @@ int apply_subsystem_event_filter(struct trace_subsystem_dir *dir,
                tracepoint_synchronize_unregister();
                filter_free_subsystem_filters(dir, tr);
                __free_filter(filter);
-               goto out_unlock;
+               return 0;
        }
 
        err = create_system_filter(dir, filter_string, &filter);
@@ -2434,8 +2432,6 @@ int apply_subsystem_event_filter(struct trace_subsystem_dir *dir,
                __free_filter(system->filter);
                system->filter = filter;
        }
-out_unlock:
-       mutex_unlock(&event_mutex);
 
        return err;
 }
@@ -2612,17 +2608,15 @@ int ftrace_profile_set_filter(struct perf_event *event, int event_id,
        struct event_filter *filter = NULL;
        struct trace_event_call *call;
 
-       mutex_lock(&event_mutex);
+       guard(mutex)(&event_mutex);
 
        call = event->tp_event;
 
-       err = -EINVAL;
        if (!call)
-               goto out_unlock;
+               return -EINVAL;
 
-       err = -EEXIST;
        if (event->filter)
-               goto out_unlock;
+               return -EEXIST;
 
        err = create_filter(NULL, call, filter_str, false, &filter);
        if (err)
@@ -2637,9 +2631,6 @@ free_filter:
        if (err || ftrace_event_is_function(call))
                __free_filter(filter);
 
-out_unlock:
-       mutex_unlock(&event_mutex);
-
        return err;
 }