On Thu, May 21, 2015 at 5:56 AM, Peter Zijlstra <[email protected]> wrote: > On Thu, May 21, 2015 at 05:35:02AM -0700, Stephane Eranian wrote: >> > Commit e979121b1b15 ("perf/x86/intel: Implement cross-HT corruption >> > bug workaround") made the situation much worse by actually setting the >> > event->hw.constraint value to NULL, so when validation and actual >> > scheduling interact we get NULL ptr derefs. >> > >> >> But x86_schedule_events() does reset the hw.constraint for each invocation: >> >> c = x86_pmu.get_event_constraints(cpuc, i, cpuc->event_list[i]); >> hwc->constraint = c; > > Yes, so if you have: > > validate_group() > > hwc->constraint = c; > Ok, you get that because validate_group() invokes x6_schedule_events() but on the fake_cpuc. This on fake_cpuc->event_list[]->hwc.
> <context switch> > > c = hwc->constraint; > > The second c might not be the first. And where does this assignment come from? For actual scheduling, we are using the actual cpuc, not fake_cpuc. Validate_group() does not modify global cpuc state. Or am I missing something? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
