linux-kernel - Re: [PATCH 23/28] locking/lockdep: Update irqsafe lock bitmaps

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Message-ID: <CAHttsrZhg9tF_dng0LEqszYaK6Y48pyKAYKLAa+yZTkgQQaBXA@mail.gmail.com>
Date:   Fri, 26 Apr 2019 14:45:31 +0800
From:   Yuyang Du <duyuyang@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     will.deacon@....com, Ingo Molnar <mingo@...nel.org>,
        Bart Van Assche <bvanassche@....org>, ming.lei@...hat.com,
        Frederic Weisbecker <frederic@...nel.org>, tglx@...utronix.de,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 23/28] locking/lockdep: Update irqsafe lock bitmaps

Thanks for review.

On Fri, 26 Apr 2019 at 03:55, Peter Zijlstra <peterz@...radead.org> wrote:
> > +     if (!dir) {
> > +             unsigned long *bitmaps[4] = {
> > +                     lock_classes_hardirq_safe,
> > +                     lock_classes_hardirq_safe_read,
> > +                     lock_classes_softirq_safe,
> > +                     lock_classes_softirq_safe_read
>
> That again should be something CPP magic using lockdep_states.h.

Yes.

> Also, that array can be static const, right? It's just an index into the
> static bitmaps.

Sure.

[...]
> > +static inline void remove_irqsafe_lock_bitmap(struct lock_class *class)
> > +{
> > +#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
> > +     unsigned long usage = class->usage_mask;
> > +
> > +     if (usage & LOCKF_USED_IN_HARDIRQ)
> > +             __clear_bit(class - lock_classes, lock_classes_hardirq_safe);
> > +     if (usage & LOCKF_USED_IN_HARDIRQ_READ)
> > +             __clear_bit(class - lock_classes, lock_classes_hardirq_safe_read);
> > +     if (usage & LOCKF_USED_IN_SOFTIRQ)
> > +             __clear_bit(class - lock_classes, lock_classes_softirq_safe);
> > +     if (usage & LOCKF_USED_IN_SOFTIRQ_READ)
> > +             __clear_bit(class - lock_classes, lock_classes_softirq_safe_read);
>
> More CPP foo required here.

Definitely.

> Also, do we really need to test, we could
> just unconditionally clear the bits.

Actually, these tests are used later for another cause: we want to
know which safe usage may be changed by zapping this lock.