Re: [PATCH v4 01/27] lockdep: Teach lockdep about "USED" <- "IN-NMI" inversions

Frederic Weisbecker
2020-02-21T22:01:41Z

On Fri, Feb 21, 2020 at 09:25:11PM +0100, Peter Zijlstra wrote:
> On Fri, Feb 21, 2020 at 10:08:55AM -0500, Steven Rostedt wrote:
> > On Fri, 21 Feb 2020 14:34:17 +0100
> > Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > > --- a/kernel/locking/lockdep.c
> > > +++ b/kernel/locking/lockdep.c
> > > @@ -379,13 +379,13 @@ void lockdep_init_task(struct task_struc
> > >
> > > void lockdep_off(void)
> > > {
> > > - current->lockdep_recursion++;
> > > + current->lockdep_recursion += BIT(16);
> > > }
> > > EXPORT_SYMBOL(lockdep_off);
> > >
> > > void lockdep_on(void)
> > > {
> > > - current->lockdep_recursion--;
> > > + current->lockdep_recursion -= BIT(16);
> > > }
> > > EXPORT_SYMBOL(lockdep_on);
> > >
> >
> > > +
> > > +static bool lockdep_nmi(void)
> > > +{
> > > + if (current->lockdep_recursion & 0xFFFF)
> >
> > Nitpick, but the association with bit 16 and this mask really should be
> > defined as a macro somewhere and not have hard coded numbers.
>
> Right, I suppose I can do something like:
>
> #define LOCKDEP_RECURSION_BITS 16
> #define LOCKDEP_OFF (1U << LOCKDEP_RECURSION_BITS)
> #define LOCKDEP_RECURSION_MASK (LOCKDEP_OFF - 1)

With that I'd say

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>