linux-kernel - Re: [PATCH v2] tracing: Make tracepoint lockdep check actually test something

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Message-ID: <20230310235653.GC1605437@hirez.programming.kicks-ass.net>
Date:   Sat, 11 Mar 2023 00:56:53 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH v2] tracing: Make tracepoint lockdep check actually test
 something

On Fri, Mar 10, 2023 at 05:28:56PM -0500, Steven Rostedt wrote:

> @@ -249,9 +248,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
>  				TP_ARGS(args),				\
>  				TP_CONDITION(cond), 0);			\
>  		if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) {		\
> -			rcu_read_lock_sched_notrace();			\
> -			rcu_dereference_sched(__tracepoint_##name.funcs);\
> -			rcu_read_unlock_sched_notrace();		\
> +			WARN_ON_ONCE(!rcu_is_watching());		\
>  		}							\
>  	}								\
>  	__DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args),		\

Yep, that makes heaps more sense. If you so care you can save one more
line and make the {} go away too.

In any case,

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>