On Tue, Aug 18, 2020 at 05:22:33PM +1000, Nicholas Piggin wrote: > Excerpts from peterz@xxxxxxxxxxxxx's message of August 12, 2020 8:35 pm: > > On Wed, Aug 12, 2020 at 06:18:28PM +1000, Nicholas Piggin wrote: > >> Excerpts from peterz@xxxxxxxxxxxxx's message of August 7, 2020 9:11 pm: > >> > > >> > What's wrong with something like this? > >> > > >> > AFAICT there's no reason to actually try and add IRQ tracing here, it's > >> > just a hand full of instructions at the most. > >> > >> Because we may want to use that in other places as well, so it would > >> be nice to have tracing. > >> > >> Hmm... also, I thought NMI context was free to call local_irq_save/restore > >> anyway so the bug would still be there in those cases? > > > > NMI code has in_nmi() true, in which case the IRQ tracing is disabled > > (except for x86 which has CONFIG_TRACE_IRQFLAGS_NMI). > > > > That doesn't help. It doesn't fix the lockdep irq state going out of > synch with the actual irq state. The code which triggered this with the > special powerpc irq disable has in_nmi() true as well. Urgh, you're talking about using lockdep_assert_irqs*() from NMI context? If not, I'm afraid I might've lost the plot a little on what exact failure case we're talking about.
