From: Keir Fraser <keir.fraser@citrix.com>
Date: Thu, 17 Jun 2010 07:52:50 +0000 (+0100)
Subject: cpuidle: redirect some hpet lock users to a new cpumask_lock
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~11912
X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https://%22%22/%22http:/www.example.com/cgi/%22https:/%22%22?a=commitdiff_plain;h=df52a1391236928859f95290a21713fc533386bf;p=xen.git

cpuidle: redirect some hpet lock users to a new cpumask_lock

The hpet channel lock was also used for prevent handle_hpet_broadcast
access other cpu's timer_deadline_start/end after other cpu was
already waken up.
This purpose can be approached via a standalone lock to remove much
spins on the hpet channel lock.

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

diff --git a/xen/arch/x86/hpet.c b/xen/arch/x86/hpet.c
index 4bfc11d9c4..d1fe7a5ee0 100644
--- a/xen/arch/x86/hpet.c
+++ b/xen/arch/x86/hpet.c
@@ -34,6 +34,7 @@ struct hpet_event_channel
     int           shift;
     s_time_t      next_event;
     cpumask_t     cpumask;
+    spinlock_t    cpumask_lock;
     spinlock_t    lock;
     void          (*event_handler)(struct hpet_event_channel *);
 
@@ -196,7 +197,7 @@ again:
     /* find all expired events */
     for_each_cpu_mask(cpu, ch->cpumask)
     {
-        spin_lock_irq(&ch->lock);
+        spin_lock_irq(&ch->cpumask_lock);
 
         if ( cpumask_test_cpu(cpu, ch->cpumask) )
         {
@@ -206,7 +207,7 @@ again:
                 next_event = per_cpu(timer_deadline_end, cpu);
         }
 
-        spin_unlock_irq(&ch->lock);
+        spin_unlock_irq(&ch->cpumask_lock);
     }
 
     /* wakeup the cpus which have an expired event. */
@@ -579,6 +580,7 @@ void hpet_broadcast_init(void)
             hpet_events[i].next_event = STIME_MAX;
             hpet_events[i].event_handler = handle_hpet_broadcast;
             spin_lock_init(&hpet_events[i].lock);
+            spin_lock_init(&hpet_events[i].cpumask_lock);
         }
 
         return;
@@ -613,6 +615,7 @@ void hpet_broadcast_init(void)
     legacy_hpet_event.idx = 0;
     legacy_hpet_event.flags = 0;
     spin_lock_init(&legacy_hpet_event.lock);
+    spin_lock_init(&legacy_hpet_event.cpumask_lock);
 
     if ( !force_hpet_broadcast )
         pv_rtc_handler = handle_rtc_once;
@@ -689,9 +692,9 @@ void hpet_broadcast_exit(void)
     if ( !reprogram_timer(this_cpu(timer_deadline_start)) )
         raise_softirq(TIMER_SOFTIRQ);
 
-    spin_lock_irq(&ch->lock);
+    spin_lock_irq(&ch->cpumask_lock);
     cpu_clear(cpu, ch->cpumask);
-    spin_unlock_irq(&ch->lock);
+    spin_unlock_irq(&ch->cpumask_lock);
 
     if ( ch != &legacy_hpet_event )
     {