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SubjectRe: [PATCH v2 06/12] perf/x86: implement cross-HT corruption bug workaround
On Thu, Oct 09, 2014 at 06:34:40PM +0200, Stephane Eranian wrote:
> From: Maria Dimakopoulou <maria.n.dimakopoulou@gmail.com>

SNIP

> +static struct event_constraint *
> +intel_get_excl_constraints(struct cpu_hw_events *cpuc, struct perf_event *event,
> + int idx, struct event_constraint *c)
> +{
> + struct event_constraint *cx;
> + struct intel_excl_cntrs *excl_cntrs = cpuc->excl_cntrs;
> + struct intel_excl_states *xl, *xlo;
> + int is_excl, i;

SNIP

> + /*
> + * Modify static constraint with current dynamic
> + * state of thread
> + *
> + * EXCLUSIVE: sibling counter measuring exclusive event
> + * SHARED : sibling counter measuring non-exclusive event
> + * UNUSED : sibling counter unused
> + */
> + for_each_set_bit(i, cx->idxmsk, X86_PMC_IDX_MAX) {
> + /*
> + * exclusive event in sibling counter
> + * our corresponding counter cannot be used
> + * regardless of our event
> + */
> + if (xl->state[i] == INTEL_EXCL_EXCLUSIVE)
> + __clear_bit(i, cx->idxmsk);

if we want to check sibling counter, shouldn't we check xlo->state[i] instead? like

if (xlo->state[i] == INTEL_EXCL_EXCLUSIVE)
__clear_bit(i, cx->idxmsk);


and also in condition below?

> + /*
> + * if measuring an exclusive event, sibling
> + * measuring non-exclusive, then counter cannot
> + * be used
> + */
> + if (is_excl && xl->state[i] == INTEL_EXCL_SHARED)
> + __clear_bit(i, cx->idxmsk);
> + }
> +
> + /*
> + * recompute actual bit weight for scheduling algorithm
> + */
> + cx->weight = hweight64(cx->idxmsk64);
> +
> + /*
> + * if we return an empty mask, then switch
> + * back to static empty constraint to avoid
> + * the cost of freeing later on
> + */
> + if (cx->weight == 0)
> + cx = &emptyconstraint;
> +

SNIP

jirka


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