On Tue, Jun 23, 2020 at 05:24:50PM +0200, Peter Zijlstra wrote:
> 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'.
>
Well, freshly merged code is using it. For example, KCSAN:
=> f1bc96210c6a ("kcsan: Make KCSAN compatible with lockdep")
=> kernel/kcsan/report.c:
void kcsan_report(...)
{
...
/*
* With TRACE_IRQFLAGS, lockdep's IRQ trace state becomes corrupted if
* we do not turn off lockdep here; this could happen due to recursion
* into lockdep via KCSAN if we detect a race in utilities used by
* lockdep.
*/
lockdep_off();
...
}
thanks,
--
Ahmed S. Darwish
Linutronix GmbH
