On Fri, Sep 11, 2020 at 10:14:41AM -0600, Logan Gunthorpe wrote: > > > On 2020-09-11 10:00 a.m., Josh Poimboeuf wrote: > > Hi Logan, > > > > Thanks for the bug report. (Sorry I missed the first one, Naresh.) > > > > The problem is that ret_from_fork() is no longer in .entry.text, so the > > following check in the FP unwinder doesn't work when ret_from_fork() > > gets interrupted. > > > > /* > > * Don't warn if the unwinder got lost due to an interrupt in entry > > * code or in the C handler before the first frame pointer got set up: > > */ > > if (state->got_irq && in_entry_code(state->ip)) > > goto the_end; > > > > If you have the ability to recreate, can you try the following patch? > > Sorry, but I can not reliably hit this bug. I hit it randomly twice last > week however, despite doing a bunch more runs this week, I haven't hit > it again. > > I can add the patch to my testing next week but I ca not give you a > definitive answer on whether this fixes the bug. > > Perhaps Naresh's test is a better reproducer.
That's ok. I forced a reproducer by putting an infinite loop in ret_from_fork to force an APIC interrupt with lockdep unwind. The patch fixes it, I'll post an official version after some more testing. -- Josh
