On Thu, May 21, 2015 at 6:29 AM, Peter Zijlstra <[email protected]> wrote: > On Thu, 2015-05-21 at 06:27 -0700, Stephane Eranian wrote: >> Or are you talking about a preemption while executing x86_schedule_events()? > > That. > > And we can of course cure that by an earlier patch I send; but I find it > a much simpler rule to just never allow modifying global state for > validation.
I can see validation being preempted, but not the context switch code path. Is that what you are talking about? You are saying validate_group() is in the middle of x86_schedule_events() using fake_cpuc, when it gets preempted. The context switch code when it loads the new thread's PMU state calls x86_schedule_events() which modifies the cpuc->event_list[]->hwc. But this is cpuc vs. fake_cpuc again. So yes, the calls nest but they do not touch the same state. And when you eventually come back to validate_group() you are back to using the fake_cpuc. So I am still not clear on how the corruption can happen. -- 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/
