Mailing List Archive

# HG changeset patch
# User kaf24@firebug.cl.cam.ac.uk
# Node ID bcf188da3ea11637abaf45d664100c209011e22e
# Parent 8531996d207f649c4375bb7fa299365205010224
Simplify vcpu_sleep_sync() and sched_adjdom(). Their
interaction with the scheduler locks was unnecessarily
complicated.

Signed-off-by: Keir Fraser <keir@xensource.com>

diff -r 8531996d207f -r bcf188da3ea1 xen/common/schedule.c
--- a/xen/common/schedule.c Thu Jan 12 20:48:51 2006
+++ b/xen/common/schedule.c Thu Jan 12 22:25:02 2006
@@ -171,20 +171,13 @@
spin_unlock_irqrestore(&schedule_data[v->processor].schedule_lock, flags);

TRACE_2D(TRC_SCHED_SLEEP, v->domain->domain_id, v->vcpu_id);
-}
+}

void vcpu_sleep_sync(struct vcpu *v)
{
vcpu_sleep_nosync(v);

- /*
- * We can be sure that the VCPU is finally descheduled after the running
- * flag is cleared and the scheduler lock is released. We also check that
- * the domain continues to be unrunnable, in case someone else wakes it.
- */
- while ( !vcpu_runnable(v) &&
- (test_bit(_VCPUF_running, &v->vcpu_flags) ||
- spin_is_locked(&schedule_data[v->processor].schedule_lock)) )
+ while ( !vcpu_runnable(v) && test_bit(_VCPUF_running, &v->vcpu_flags) )
cpu_relax();

sync_vcpu_execstate(v);
@@ -314,68 +307,42 @@
{
struct domain *d;
struct vcpu *v;
- int cpu;
-#if NR_CPUS <=32
- unsigned long have_lock;
- #else
- unsigned long long have_lock;
-#endif
- int succ;
-
- #define __set_cpu_bit(cpu, data) data |= ((typeof(data))1)<<cpu
- #define __get_cpu_bit(cpu, data) (data & ((typeof(data))1)<<cpu)
- #define __clear_cpu_bits(data) data = ((typeof(data))0)

- if ( cmd->sched_id != ops.sched_id )
- return -EINVAL;
-
- if ( cmd->direction != SCHED_INFO_PUT && cmd->direction != SCHED_INFO_GET )
+ if ( (cmd->sched_id != ops.sched_id) ||
+ ((cmd->direction != SCHED_INFO_PUT) &&
+ (cmd->direction != SCHED_INFO_GET)) )
return -EINVAL;

d = find_domain_by_id(cmd->domain);
if ( d == NULL )
return -ESRCH;

- /* acquire locks on all CPUs on which vcpus of this domain run */
- do {
- succ = 0;
- __clear_cpu_bits(have_lock);
- for_each_vcpu ( d, v )
- {
- cpu = v->processor;
- if ( !__get_cpu_bit(cpu, have_lock) )
- {
- /* if we don't have a lock on this CPU: acquire it*/
- if ( spin_trylock(&schedule_data[cpu].schedule_lock) )
- {
- /*we have this lock!*/
- __set_cpu_bit(cpu, have_lock);
- succ = 1;
- }
- else
- {
- /*we didn,t get this lock -> free all other locks too!*/
- for ( cpu = 0; cpu < NR_CPUS; cpu++ )
- if ( __get_cpu_bit(cpu, have_lock) )
- spin_unlock(&schedule_data[cpu].schedule_lock);
- /* and start from the beginning! */
- succ = 0;
- /* leave the "for_each_domain_loop" */
- break;
- }
- }
- }
- } while ( !succ );
+ /*
+ * Most VCPUs we can simply pause. If we are adjusting this VCPU then
+ * we acquire the local schedule_lock to guard against concurrent updates.
+ */
+ for_each_vcpu ( d, v )
+ {
+ if ( v == current )
+ spin_lock_irq(&schedule_data[smp_processor_id()].schedule_lock);
+ else
+ vcpu_pause(v);
+ }

SCHED_OP(adjdom, d, cmd);

- for ( cpu = 0; cpu < NR_CPUS; cpu++ )
- if ( __get_cpu_bit(cpu, have_lock) )
- spin_unlock(&schedule_data[cpu].schedule_lock);
- __clear_cpu_bits(have_lock);
-
TRACE_1D(TRC_SCHED_ADJDOM, d->domain_id);
+
+ for_each_vcpu ( d, v )
+ {
+ if ( v == current )
+ spin_unlock_irq(&schedule_data[smp_processor_id()].schedule_lock);
+ else
+ vcpu_unpause(v);
+ }
+
put_domain(d);
+
return 0;
}


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