Commit 78347cdb authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

cpufreq: governor: Reset sample delay in store_sampling_rate() 



If store_sampling_rate() updates the sample delay when the ondemand
governor is in the middle of its high/low dance (OD_SUB_SAMPLE sample
type is set), the governor will still do the bottom half of the
previous sample which may take too much time.

To prevent that from happening, change store_sampling_rate() to always
reset the sample delay to 0 which also is consistent with the new
behavior of cpufreq_governor_limits().

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
parent 4cccf755

drivers/cpufreq/cpufreq_governor.c

+4 −12
Original line number Diff line number Diff line
@@ -38,10 +38,6 @@ EXPORT_SYMBOL_GPL(dbs_data_mutex); 
 * reducing the sampling rate, we need to make the new value effective

 * immediately.

 *

 * On the other hand, if new rate is larger than the old, then we may evaluate

 * the load too soon, and it might we worth updating sample_delay_ns then as

 * well.

 *

 * This must be called with dbs_data->mutex held, otherwise traversing

 * policy_dbs_list isn't safe.

 */
@@ -69,18 +65,14 @@ ssize_t store_sampling_rate(struct dbs_data *dbs_data, const char *buf, 
		 * really doesn't matter.  If the read returns a value that's

		 * too big, the sample will be skipped, but the next invocation

		 * of dbs_update_util_handler() (when the update has been

		 * completed) will take a sample.  If the returned value is too

		 * small, the sample will be taken immediately, but that isn't a

		 * problem, as we want the new rate to take effect immediately

		 * anyway.

		 * completed) will take a sample.

		 *

		 * If this runs in parallel with dbs_work_handler(), we may end

		 * up overwriting the sample_delay_ns value that it has just

		 * written, but the difference should not be too big and it will

		 * be corrected next time a sample is taken, so it shouldn't be

		 * significant.

		 * written, but it will be corrected next time a sample is

		 * taken, so it shouldn't be significant.

		 */

		gov_update_sample_delay(policy_dbs, dbs_data->sampling_rate);

		gov_update_sample_delay(policy_dbs, 0);

		mutex_unlock(&policy_dbs->timer_mutex);

	}

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