MAX_STACK_TRACE_ENTRIES
static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
nr_stack_trace_entries, MAX_STACK_TRACE_ENTRIES);