linux-kernel - Re: [PATCH v4 7/8] lockdep: Change hardirq{s_enabled,

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Message-ID: <20200630094019.GL4800@hirez.programming.kicks-ass.net>
Date:   Tue, 30 Jun 2020 11:40:19 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Ahmed S. Darwish" <a.darwish@...utronix.de>
Cc:     mingo@...nel.org, will@...nel.org, tglx@...utronix.de,
        x86@...nel.org, linux-kernel@...r.kernel.org, rostedt@...dmis.org,
        bigeasy@...utronix.de, davem@...emloft.net,
        sparclinux@...r.kernel.org, mpe@...erman.id.au,
        linuxppc-dev@...ts.ozlabs.org, heiko.carstens@...ibm.com,
        linux-s390@...r.kernel.org, linux@...linux.org.uk
Subject: Re: [PATCH v4 7/8] lockdep: Change hardirq{s_enabled,_context} to
 per-cpu variables

On Tue, Jun 30, 2020 at 07:59:39AM +0200, Ahmed S. Darwish wrote:
> Peter Zijlstra wrote:
> 
> ...
> 
> > -#define lockdep_assert_irqs_disabled()	do {			\
> > -		WARN_ONCE(debug_locks && !current->lockdep_recursion &&	\
> > -			  current->hardirqs_enabled,			\
> > -			  "IRQs not disabled as expected\n");		\
> > -	} while (0)
> 
> ...
> 
> > +#define lockdep_assert_irqs_disabled()				\
> > +do {									\
> > +	WARN_ON_ONCE(debug_locks && this_cpu_read(hardirqs_enabled));	\
> > +} while (0)
> 
> I think it would be nice to keep the "IRQs not disabled as expected"
> message. It makes the lockdep splat much more readable.
> 
> This is similarly the case for the v3 lockdep preemption macros:
> 
>   https://lkml.kernel.org/r/20200630054452.3675847-5-a.darwish@linutronix.de
> 
> I did not add a message though to get in-sync with the IRQ macros above.

Hurmph.. the file:line output of a splat is usually all I look at, also
__WARN_printf() generates such atrocious crap code that try and not use
it.

I suppose I should do a __WARN_str() or something, but then people are
unlikely to want to use that, too much variation etc. :/

Cursed if you do, cursed if you don't.