linux-kernel - Re: [PATCH] tracing, hardirq: Do not test lockdep on irq trace points when disabled

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Date:   Wed, 8 Mar 2023 16:41:37 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Ross Zwisler <zwisler@...gle.com>
Subject: Re: [PATCH] tracing, hardirq: Do not test lockdep on irq trace
 points when disabled

On Wed, 8 Mar 2023 11:56:06 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> index e299f29375bb..d3a221158ab1 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -260,9 +260,7 @@ 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),		\


This fixes the hung tasks as well. I'll push this through instead, and mark
it for stable. As the old check was incorrect for a long time.

-- Steve