tracing: Use __this_cpu_read() in trace_event_buffer_lock_reserver()

The value read by this_cpu_read() is used later and its use is expected to
stay on the same CPU as being read. But this_cpu_read() does not warn if
it is called without preemption disabled, where as __this_cpu_read() will
check if preemption is disabled on CONFIG_DEBUG_PREEMPT

Currently all callers have preemption disabled, but there may be new
callers in the future that may not.

Link: https://lkml.kernel.org/r/20211130024318.698165354@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4821fe6..2e87b7b 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2746,7 +2746,7 @@ trace_event_buffer_lock_reserve(struct trace_buffer **current_rb,
 
        if (!tr->no_filter_buffering_ref &&
            (trace_file->flags & (EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) &&
-           (entry = this_cpu_read(trace_buffered_event))) {
+           (entry = __this_cpu_read(trace_buffered_event))) {
                /*
                 * Filtering is on, so try to use the per cpu buffer first.
                 * This buffer will simulate a ring_buffer_event,