static void get_recent_times(struct psi_group *group, int cpu,
			     enum psi_aggregators aggregator, u32 *times,
			     u32 *pchanged_states)
{
	struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
	u64 now, state_start;
	enum psi_states s;
	unsigned int seq;
	u32 state_mask;

	*pchanged_states = 0;

	/* Snapshot a coherent view of the CPU state */
	do {
		seq = read_seqcount_begin(&groupc->seq);
		now = cpu_clock(cpu);
		memcpy(times, groupc->times, sizeof(groupc->times));
		state_mask = groupc->state_mask;
		state_start = groupc->state_start;
	} while (read_seqcount_retry(&groupc->seq, seq));

	/* Calculate state time deltas against the previous snapshot */
	for (s = 0; s < NR_PSI_STATES; s++) {
		u32 delta;
		/*
		 * In addition to already concluded states, we also
		 * incorporate currently active states on the CPU,
		 * since states may last for many sampling periods.
		 *
		 * This way we keep our delta sampling buckets small
		 * (u32) and our reported pressure close to what's
		 * actually happening.
		 */
		if (state_mask & (1 << s))
			times[s] += now - state_start;

		delta = times[s] - groupc->times_prev[aggregator][s];
		groupc->times_prev[aggregator][s] = times[s];

		times[s] = delta;
		if (delta)
			*pchanged_states |= (1 << s);
	}
}
Unknown