[PATCH v1] cpuidle: Add sanity check for exit latency and target residency

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

Make __cpuidle_driver_init() sanitize CPU idle states so that the exit
latency of a given state is not greater than its target residency which
would break cpuidle assumptions.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
 drivers/cpuidle/driver.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -193,6 +193,16 @@ static void __cpuidle_driver_init(struct
 			s->exit_latency_ns =  0;
 		else
 			s->exit_latency = div_u64(s->exit_latency_ns, NSEC_PER_USEC);
+
+		/*
+		 * Ensure that the exit latency of a CPU idle state does not
+		 * exceed its target residency which is assumed in cpuidle in
+		 * multiple places.
+		 */
+		if (s->exit_latency_ns > s->target_residency_ns) {
+			s->target_residency_ns = s->exit_latency_ns;
+			s->target_residency = s->exit_latency;
+		}
 	}
 }