# HG changeset patch
# User Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
# Date 1300113178 -3600
# Node ID 9d164ce877a75cab847b8a6e0114230807d5acd6
# Parent  84bacd800bf88e37434d49547ad8224be46e2a52
Avoid endless loop for vcpu migration

On multi-thread multi-core systems an endless loop can occur in vcpu_migrate()
with credit scheduler. Avoid this loop by changing the interface of pick_cpu
to indicate a repeated call in this case.

Signed-off-by: juergen.gross@xxxxxxxxxxxxxx

diff -r 84bacd800bf8 -r 9d164ce877a7 xen/common/sched_arinc653.c
--- a/xen/common/sched_arinc653.c	Sat Mar 12 13:20:51 2011 +0000
+++ b/xen/common/sched_arinc653.c	Mon Mar 14 15:32:58 2011 +0100
@@ -612,7 +612,7 @@ a653sched_do_schedule(
  * @return          Number of selected physical CPU
  */
 static int
-a653sched_pick_cpu(const struct scheduler *ops, struct vcpu *vc)
+a653sched_pick_cpu(const struct scheduler *ops, struct vcpu *vc, int proposal)
 {
     /* this implementation only supports one physical CPU */
     return 0;
diff -r 84bacd800bf8 -r 9d164ce877a7 xen/common/sched_credit.c
--- a/xen/common/sched_credit.c	Sat Mar 12 13:20:51 2011 +0000
+++ b/xen/common/sched_credit.c	Mon Mar 14 15:32:58 2011 +0100
@@ -459,7 +459,7 @@ __csched_vcpu_is_migrateable(struct vcpu
 }
 
 static int
-_csched_cpu_pick(const struct scheduler *ops, struct vcpu *vc, bool_t commit)
+csched_cpu_pick(const struct scheduler *ops, struct vcpu *vc, int proposal)
 {
     cpumask_t cpus;
     cpumask_t idlers;
@@ -531,7 +531,7 @@ _csched_cpu_pick(const struct scheduler 
                   && (weight_cpu * migrate_factor < weight_nxt) ) )
         {
             cpu = cycle_cpu(CSCHED_PCPU(nxt)->idle_bias, nxt_idlers);
-            if ( commit )
+            if ( proposal == -1 )
                CSCHED_PCPU(nxt)->idle_bias = cpu;
             cpus_andnot(cpus, cpus, per_cpu(cpu_sibling_map, cpu));
         }
@@ -542,12 +542,6 @@ _csched_cpu_pick(const struct scheduler 
     }
 
     return cpu;
-}
-
-static int
-csched_cpu_pick(const struct scheduler *ops, struct vcpu *vc)
-{
-    return _csched_cpu_pick(ops, vc, 1);
 }
 
 static inline void
@@ -632,7 +626,7 @@ csched_vcpu_acct(struct csched_private *
     {
         __csched_vcpu_acct_start(prv, svc);
     }
-    else if ( _csched_cpu_pick(ops, current, 0) != cpu )
+    else if ( csched_cpu_pick(ops, current, cpu) != cpu )
     {
         CSCHED_VCPU_STAT_CRANK(svc, migrate_r);
         CSCHED_STAT_CRANK(migrate_running);
diff -r 84bacd800bf8 -r 9d164ce877a7 xen/common/sched_credit2.c
--- a/xen/common/sched_credit2.c	Sat Mar 12 13:20:51 2011 +0000
+++ b/xen/common/sched_credit2.c	Mon Mar 14 15:32:58 2011 +0100
@@ -1350,7 +1350,7 @@ out:
 }
 
 static int
-csched_cpu_pick(const struct scheduler *ops, struct vcpu *vc)
+csched_cpu_pick(const struct scheduler *ops, struct vcpu *vc, int proposal)
 {
     struct csched_vcpu * const svc = CSCHED_VCPU(vc);
     int new_cpu;
diff -r 84bacd800bf8 -r 9d164ce877a7 xen/common/sched_sedf.c
--- a/xen/common/sched_sedf.c	Sat Mar 12 13:20:51 2011 +0000
+++ b/xen/common/sched_sedf.c	Mon Mar 14 15:32:58 2011 +0100
@@ -442,7 +442,7 @@ static void sedf_destroy_domain(const st
     sedf_free_domdata(ops, d->sched_priv);
 }
 
-static int sedf_pick_cpu(const struct scheduler *ops, struct vcpu *v)
+static int sedf_pick_cpu(const struct scheduler *ops, struct vcpu *v, int proposal)
 {
     cpumask_t online_affinity;
     cpumask_t *online;
diff -r 84bacd800bf8 -r 9d164ce877a7 xen/common/schedule.c
--- a/xen/common/schedule.c	Sat Mar 12 13:20:51 2011 +0000
+++ b/xen/common/schedule.c	Mon Mar 14 15:32:58 2011 +0100
@@ -393,9 +393,10 @@ static void vcpu_migrate(struct vcpu *v)
 static void vcpu_migrate(struct vcpu *v)
 {
     unsigned long flags;
-    unsigned int old_cpu, new_cpu;
+    unsigned int old_cpu, new_cpu, proposal;
     spinlock_t *old_lock, *new_lock;
 
+    proposal = -1;
     old_cpu = new_cpu = v->processor;
     for ( ; ; )
     {
@@ -430,10 +431,11 @@ static void vcpu_migrate(struct vcpu *v)
         old_cpu = v->processor;
         if ( old_lock == per_cpu(schedule_data, old_cpu).schedule_lock )
         {
-            new_cpu = SCHED_OP(VCPU2OP(v), pick_cpu, v);
+            new_cpu = SCHED_OP(VCPU2OP(v), pick_cpu, v, proposal);
             if ( (new_lock == per_cpu(schedule_data, new_cpu).schedule_lock) &&
                  cpu_isset(new_cpu, v->domain->cpupool->cpu_valid) )
                 break;
+            proposal = new_cpu;
         }
 
         if ( old_lock != new_lock )
diff -r 84bacd800bf8 -r 9d164ce877a7 xen/include/xen/sched-if.h
--- a/xen/include/xen/sched-if.h	Sat Mar 12 13:20:51 2011 +0000
+++ b/xen/include/xen/sched-if.h	Mon Mar 14 15:32:58 2011 +0100
@@ -167,7 +167,7 @@ struct scheduler {
     struct task_slice (*do_schedule) (const struct scheduler *, s_time_t,
                                       bool_t tasklet_work_scheduled);
 
-    int          (*pick_cpu)       (const struct scheduler *, struct vcpu *);
+    int          (*pick_cpu)       (const struct scheduler *, struct vcpu *, int proposal);
     int          (*adjust)         (const struct scheduler *, struct domain *,
                                     struct xen_domctl_scheduler_op *);
     int          (*adjust_global)  (const struct scheduler *,