tracing: Ensure optimized hashing works

If ever PID_MAX_DEFAULT changes, it must be compatible with tracing
hashmaps assumptions.

Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Link: https://lore.kernel.org/[email protected]
Link: https://lore.kernel.org/r/[email protected]/
Signed-off-by: Michal Koutný <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: Werkov

kernel/trace/trace_sched_switch.c

@@ -247,6 +247,8 @@ int trace_save_cmdline(struct task_struct *tsk)
 	if (!tsk->pid)
 		return 1;
 
+	BUILD_BUG_ON(!is_power_of_2(PID_MAX_DEFAULT));
+
 	tpid = tsk->pid & (PID_MAX_DEFAULT - 1);
 
 	/*