Commit 1b273124 authored Feb 28, 2024 by Steven Rostedt (Google)

tracepoints: Use WARN() and not WARN_ON() for warnings

There are two WARN_ON*() warnings in tracepoint.h that deal with RCU
usage. But when they trigger, especially from using a TRACE_EVENT()
macro, the information is not very helpful and is confusing:

 ------------[ cut here ]------------
 WARNING: CPU: 0 PID: 0 at include/trace/events/lock.h:24 lock_acquire+0x2b2/0x2d0

Where the above warning takes you to:

 TRACE_EVENT(lock_acquire,  <<<--- line 24 in lock.h

	TP_PROTO(struct lockdep_map *lock, unsigned int subclass,
		int trylock, int read, int check,
		struct lockdep_map *next_lock, unsigned long ip),
	[..]

Change the WARN_ON_ONCE() to WARN_ONCE() and add a string that allows
someone to search for exactly where the bug happened.

Link: https://lore.kernel.org/linux-trace-kernel/20240228133112.0d64fb1b@gandalf.local.home



Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Borislav Petkov <bp@alien8.de>
Tested-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

parent d6cb38e1

include/linux/tracepoint.h

+4 −2

Original line number	Diff line number	Diff line
		@@ -199,7 +199,8 @@ static inline struct tracepoint tracepoint_ptr_deref(tracepoint_ptr_t p)
		if (!(cond)) \
		return; \
		\
		if (WARN_ON_ONCE(RCUIDLE_COND(rcuidle))) \
		if (WARN_ONCE(RCUIDLE_COND(rcuidle), \
		"Bad RCU usage for tracepoint")) \
		return; \
		\
		/* keep srcu and sched-rcu usage consistent */ \
		@@ -259,7 +260,8 @@ static inline struct tracepoint tracepoint_ptr_deref(tracepoint_ptr_t p)
		TP_ARGS(args), \
		TP_CONDITION(cond), 0); \
		if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \
		WARN_ON_ONCE(!rcu_is_watching()); \
		WARN_ONCE(!rcu_is_watching(), \
		"RCU not watching for tracepoint"); \
		} \
		} \
		__DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args), \