tracing: Fix wakeup tracers on failure of acquiring calltime

The functions wakeup_graph_entry() and wakeup_graph_return() both call
func_prolog_preempt_disable() that will test if the data->disable is
already set and if not, increment it and disable preemption. If it was
set, it returns false and the caller exits.

The caller of this function must decrement the disable counter, but misses
doing so if the calltime fails to be acquired.

Instead of exiting out when calltime is NULL, change the logic to do the
work if it is not NULL and still do the clean up at the end of the
function if it is NULL.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20251008114835.027b878a@gandalf.local.home
Fixes: a485ea9e3ef3 ("tracing: Fix irqsoff and wakeup latency tracers when using function graph")
Reported-by: Sasha Levin <sashal@kernel.org>
Closes: https://lore.kernel.org/linux-trace-kernel/20251006175848.1906912-1-sashal@kernel.org/
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index bf1cb80742aed7b58dd6da7509f97c9039940532..e3f2e4f56faa42b0df3de967640c1adb72d99fcd 100644 (file)
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -138,12 +138,10 @@ static int wakeup_graph_entry(struct ftrace_graph_ent *trace,
                return 0;
 
        calltime = fgraph_reserve_data(gops->idx, sizeof(*calltime));
-       if (!calltime)
-               return 0;
-
-       *calltime = trace_clock_local();
-
-       ret = __trace_graph_entry(tr, trace, trace_ctx);
+       if (calltime) {
+               *calltime = trace_clock_local();
+               ret = __trace_graph_entry(tr, trace, trace_ctx);
+       }
        local_dec(&data->disabled);
        preempt_enable_notrace();
 
@@ -169,12 +167,10 @@ static void wakeup_graph_return(struct ftrace_graph_ret *trace,
        rettime = trace_clock_local();
 
        calltime = fgraph_retrieve_data(gops->idx, &size);
-       if (!calltime)
-               return;
+       if (calltime)
+               __trace_graph_return(tr, trace, trace_ctx, *calltime, rettime);
 
-       __trace_graph_return(tr, trace, trace_ctx, *calltime, rettime);
        local_dec(&data->disabled);
-
        preempt_enable_notrace();
        return;
 }