From: Keir Fraser <keir.fraser@citrix.com>
Date: Wed, 10 Sep 2008 10:16:26 +0000 (+0100)
Subject: CPUIDLE: Avoid remnant LAPIC timer intr while force hpetbroadcast
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~14111^2~11
X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https:/%22bookmarks://%22Dat/%22http:/www.example.com/cgi/%22https:/%22bookmarks:/%22Dat?a=commitdiff_plain;h=789dc790f316debd10fd808a4f13e08c60930d1a;p=xen.git

CPUIDLE: Avoid remnant LAPIC timer intr while force hpetbroadcast

LAPIC will stop during C3, and resume to work after exit from
C3. Considering below case:
The LAPIC timer was programmed to expire after 1000us, but CPU enter
C3 after 100us and exit C3 at 9xxus.

   0us: reprogram_timer(1000us)
 100us: entry C3, LAPIC timer stop
 9xxus: exit C3 due to unexpected event, LAPIC timer continue running
10xxus: reprogram_timer(1000us), fail due to the past expiring time.
......: no timer softirq raised, no change to LAPIC timer.
......: if entry C3 again, HPET will be forced reprogramed to
 now+small_slop.
......: if entry C2, no change to LAPIC.
18xxus: LAPIC timer expires unexpectedly if no C3 entries after
 10xxus.

Signed-off-by: Wei Gang <gang.wei@intel.com>
---

diff --git a/xen/arch/x86/hpet.c b/xen/arch/x86/hpet.c
index 31028cc2a6..3857cb0af6 100644
--- a/xen/arch/x86/hpet.c
+++ b/xen/arch/x86/hpet.c
@@ -233,7 +233,15 @@ void hpet_broadcast_exit(void)
 
     if ( cpu_test_and_clear(cpu, ch->cpumask) )
     {
-        reprogram_timer(per_cpu(timer_deadline, cpu));
+        if ( !reprogram_timer(per_cpu(timer_deadline, cpu)) )
+        {
+            /*
+             * The deadline must have passed -- trigger timer work now.
+             * Also cancel any outstanding LAPIC event.
+             */
+            reprogram_timer(0);
+            raise_softirq(TIMER_SOFTIRQ);
+        }
 
         if ( cpus_empty(ch->cpumask) && ch->next_event != STIME_MAX )
             reprogram_hpet_evt_channel(ch, STIME_MAX, 0, 0);