xen: Add support for preemption

[deliverable/linux.git] / arch / i386 / xen / time.c

diff --git a/arch/i386/xen/time.c b/arch/i386/xen/time.c
index aeb04cf5dbf1cd4ed7139d3aea2a5a9074f06800..51fdabf1fd4dd813645737cbab05c6894227d0ae 100644 (file)
--- a/arch/i386/xen/time.c
+++ b/arch/i386/xen/time.c
@@ -88,7 +88,7 @@ static void get_runstate_snapshot(struct vcpu_runstate_info *res)
        u64 state_time;
        struct vcpu_runstate_info *state;
 
-       preempt_disable();
+       BUG_ON(preemptible());
 
        state = &__get_cpu_var(runstate);
 
@@ -103,8 +103,6 @@ static void get_runstate_snapshot(struct vcpu_runstate_info *res)
                *res = *state;
                barrier();
        } while (get64(&state->state_entry_time) != state_time);
-
-       preempt_enable();
 }
 
 static void setup_runstate_info(int cpu)
@@ -179,9 +177,19 @@ static void do_stolen_accounting(void)
 unsigned long long xen_sched_clock(void)
 {
        struct vcpu_runstate_info state;
-       cycle_t now = xen_clocksource_read();
+       cycle_t now;
+       u64 ret;
        s64 offset;
 
+       /*
+        * Ideally sched_clock should be called on a per-cpu basis
+        * anyway, so preempt should already be disabled, but that's
+        * not current practice at the moment.
+        */
+       preempt_disable();
+
+       now = xen_clocksource_read();
+
        get_runstate_snapshot(&state);
 
        WARN_ON(state.state != RUNSTATE_running);
@@ -190,9 +198,13 @@ unsigned long long xen_sched_clock(void)
        if (offset < 0)
                offset = 0;
 
-       return state.time[RUNSTATE_blocked] +
+       ret = state.time[RUNSTATE_blocked] +
                state.time[RUNSTATE_running] +
                offset;
+
+       preempt_enable();
+
+       return ret;
 }