From a5a8a9e45d02c2bfabb06c13278c4bd3895267c0 Mon Sep 17 00:00:00 2001
From: Con Kolivas <kernel@kolivas.org>
Date: Sat, 5 Nov 2016 09:27:36 +1100
Subject: [PATCH 05/18] Special case calls of schedule_timeout(1) to use the
 min hrtimeout of 1ms, working around low Hz resolutions.

---
 kernel/time/timer.c |   17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

Index: linux-4.11-ck1/kernel/time/timer.c
===================================================================
--- linux-4.11-ck1.orig/kernel/time/timer.c	2017-05-12 13:25:54.835577214 +1000
+++ linux-4.11-ck1/kernel/time/timer.c	2017-05-12 13:25:54.835577214 +1000
@@ -1709,6 +1709,19 @@ signed long __sched schedule_timeout(sig
 
 	expire = timeout + jiffies;
 
+#ifdef CONFIG_HIGH_RES_TIMERS
+	if (timeout == 1 && hrtimer_resolution < NSEC_PER_SEC / HZ) {
+		/*
+		 * Special case 1 as being a request for the minimum timeout
+		 * and use highres timers to timeout after 1ms to workaround
+		 * the granularity of low Hz tick timers.
+		 */
+		if (!schedule_min_hrtimeout())
+			return 0;
+		goto out_timeout;
+	}
+#endif
+
 	setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);
 	__mod_timer(&timer, expire, false);
 	schedule();
@@ -1716,10 +1729,10 @@ signed long __sched schedule_timeout(sig
 
 	/* Remove the timer from the object tracker */
 	destroy_timer_on_stack(&timer);
-
+out_timeout:
 	timeout = expire - jiffies;
 
- out:
+out:
 	return timeout < 0 ? 0 : timeout;
 }
 EXPORT_SYMBOL(schedule_timeout);