From e7b320c91633ed9d8fd869af7231f69bedaa5a3f Mon Sep 17 00:00:00 2001
From: Giovanni Di Sirio <gdisirio@gmail.com>
Date: Mon, 10 Oct 2016 12:20:18 +0000
Subject: [PATCH] Fixed bug #784.

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/branches/stable_16.1.x@9856 35acf78f-673a-0410-8e92-d51de3d6d3f4
---
 os/rt/src/chvt.c | 25 +++++++++++++++++++------
 readme.txt       |  1 +
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/os/rt/src/chvt.c b/os/rt/src/chvt.c
index 214e8a7b6..e3b44c2f2 100644
--- a/os/rt/src/chvt.c
+++ b/os/rt/src/chvt.c
@@ -131,23 +131,36 @@ void chVTDoSetI(virtual_timer_t *vtp, systime_t delay,
       return;
     }
 
-    /* Special case where the timer will be placed as first element in a
-       non-empty list, the alarm needs to be recalculated.*/
-    delta = now + delay - ch.vtlist.vt_lasttime;
-    if (delta < ch.vtlist.vt_next->vt_delta) {
+    /* Pointer to the first element in the delta list, which is non-empty.*/
+    p = ch.vtlist.vt_next;
 
-      /* New alarm deadline.*/
+    /* Delay as delta from 'lasttime'. Note, it can overflow and the value
+       becomes lower than 'now'.*/
+    delta = now - ch.vtlist.vt_lasttime + delay;
+
+    if (delta < now - ch.vtlist.vt_lasttime) {
+      /* Scenario where a very large delay excedeed the numeric range, it
+         requires a special handling. We need to skip the first element and
+         adjust the delta to wrap back in the previous numeric range.*/
+      delta -= p->vt_delta;
+      p = p->vt_next;
+    }
+    else if (delta < p->vt_delta) {
+     /* A small delay that will become the first element in the delta list
+        and next deadline.*/
       port_timer_set_alarm(ch.vtlist.vt_lasttime + delta);
     }
   }
 #else /* CH_CFG_ST_TIMEDELTA == 0 */
   /* Delta is initially equal to the specified delay.*/
   delta = delay;
+
+  /* Pointer to the first element in the delta list.*/
+  p = ch.vtlist.vt_next;
 #endif /* CH_CFG_ST_TIMEDELTA == 0 */
 
   /* The delta list is scanned in order to find the correct position for
      this timer. */
-  p = ch.vtlist.vt_next;
   while (p->vt_delta < delta) {
     delta -= p->vt_delta;
     p = p->vt_next;
diff --git a/readme.txt b/readme.txt
index ac937acf7..e2cd28afb 100644
--- a/readme.txt
+++ b/readme.txt
@@ -73,6 +73,7 @@
 *****************************************************************************
 
 *** 16.1.6 ***
+- RT:  Fixed tick-less mode can fail in RT for very large delays (bug #784).
 - HAL: Fixed STM32L0xx CCIPR initialization (bug #783).
 - HAL: Fixed STM32F105 port not compiling (bug #782).
 - HAL: Fixed wrong registry for STM32F205xx and STM32F215xx port