linux-kernel - Re: [PATCH v1 07/25] lockdep: Add preemption disabled assertion API

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Message-ID: <20200522175503.GQ325280@hirez.programming.kicks-ass.net>
Date:   Fri, 22 May 2020 19:55:03 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Ahmed S. Darwish" <a.darwish@...utronix.de>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        "Sebastian A. Siewior" <bigeasy@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 07/25] lockdep: Add preemption disabled assertion API

On Tue, May 19, 2020 at 11:45:29PM +0200, Ahmed S. Darwish wrote:
> diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
> index 206774ac6946..54c929ea5b98 100644
> --- a/include/linux/lockdep.h
> +++ b/include/linux/lockdep.h
> @@ -702,6 +702,14 @@ do {									\
>  			  "Not in hardirq as expected\n");		\
>  	} while (0)
>  
> +/*
> + * Don't define this assertion here to avoid a call-site's header file
> + * dependency on sched.h task_struct current. This is needed by call
> + * sites that are inline defined at header files already included by
> + * sched.h.
> + */
> +void lockdep_assert_preemption_disabled(void);

So how about:

#if defined(CONFIG_PREEMPT_COUNT) && defined(CONFIG_TRACE_IRQFLAGS)
#define lockdep_assert_preemption_disabled() do { \
		WARN_ON(debug_locks && !preempt_count() && \
			current->hardirqs_enabled); \
	} while (0)
#else
#define lockdep_assert_preemption_disabled() do { } while (0)
#endif

That is both more consistent with the things you claim it's modelled
after and also completely avoids that header dependency.