tracing: Ensure optimized hashing works

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

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250924113810.2433478-1-mkoutny@suse.com
Link: https://lore.kernel.org/r/20240409110126.651e94cb@gandalf.local.home/
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index 518dfc74347aff30584dd86f040ffd064de40d03..c46d584ded3b56378889c747bf8c5f37adf7a17a 100644 (file)
--- a/kernel/trace/trace_sched_switch.c
+++ b/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);
 
        /*