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

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Message-ID: <20200623152450.GM4817@hirez.programming.kicks-ass.net>
Date:   Tue, 23 Jun 2020 17:24:50 +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 23, 2020 at 05:00:31PM +0200, Ahmed S. Darwish wrote:
> On Tue, Jun 23, 2020 at 10:36:52AM +0200, 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_enabled()					\
> > +do {									\
> > +	WARN_ON_ONCE(debug_locks && !this_cpu_read(hardirqs_enabled));	\
> > +} while (0)
> >
> 
> Can we add a small comment on top of lockdep_off(), stating that lockdep
> IRQ tracking will still be kept after a lockdep_off call?

That would only legitimize lockdep_off(). The only comment I want to put
on that is: "if you use this, you're doing it wrong'.