perf_counter: Fix swcounter context invariance

static int perf_swcounter_is_counting(struct perf_counter *counter)

{

	struct perf_counter_context *ctx;

	unsigned long flags;

	int count;

	/*

	 * The counter is active, we're good!

	 */

	if (counter->state == PERF_COUNTER_STATE_ACTIVE)

		return 1;

	/*

	 * The counter is off/error, not counting.

	 */

	if (counter->state != PERF_COUNTER_STATE_INACTIVE)

		return 0;

	/*

	 * If the counter is inactive, it could be just because

	 * its task is scheduled out, or because it's in a group

	 * which could not go on the PMU.  We want to count in

	 * the first case but not the second.  If the context is

	 * currently active then an inactive software counter must

	 * be the second case.  If it's not currently active then

	 * we need to know whether the counter was active when the

	 * context was last active, which we can determine by

	 * comparing counter->tstamp_stopped with ctx->time.

	 *

	 * We are within an RCU read-side critical section,

	 * which protects the existence of *ctx.

	 * The counter is inactive, if the context is active

	 * we're part of a group that didn't make it on the 'pmu',

	 * not counting.

	 */

	ctx = counter->ctx;

	spin_lock_irqsave(&ctx->lock, flags);

	count = 1;

	/* Re-check state now we have the lock */

	if (counter->state < PERF_COUNTER_STATE_INACTIVE ||

	    counter->ctx->is_active ||

	    counter->tstamp_stopped < ctx->time)

		count = 0;

	spin_unlock_irqrestore(&ctx->lock, flags);

	return count;

	if (counter->ctx->is_active)

		return 0;

	/*

	 * We're inactive and the context is too, this means the

	 * task is scheduled out, we're counting events that happen

	 * to us, like migration events.

	 */

	return 1;

}

static int perf_swcounter_match(struct perf_counter *counter,