sched: fix locking of remove_vcpu() in credit1

In fact, csched_vcpu_remove() (i.e., the credit1
implementation of remove_vcpu()) manipulates runqueues,
so holding the runqueue lock is necessary.

However, the vCPU just can't be on the runqueue, when
the function is called. We can therefore ASSERT() that,
and avoid doing any runqueue manipulations (rather than
adding the runqueue locking around it).

Also, while there, *_lock_irq() (for the private lock) is
enough, there is no need to *_lock_irqsave().

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>

diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index 9eb457c65a02580f20f6dc5439305365b9b3dad6..72a210911a3edb7146906d778941b36fecef06a1 100644 (file)
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -933,28 +933,25 @@ csched_vcpu_remove(const struct scheduler *ops, struct vcpu *vc)
     struct csched_private *prv = CSCHED_PRIV(ops);
     struct csched_vcpu * const svc = CSCHED_VCPU(vc);
     struct csched_dom * const sdom = svc->sdom;
-    unsigned long flags;
 
     SCHED_STAT_CRANK(vcpu_remove);
 
+    ASSERT(!__vcpu_on_runq(svc));
+
     if ( test_and_clear_bit(CSCHED_FLAG_VCPU_PARKED, &svc->flags) )
     {
         SCHED_STAT_CRANK(vcpu_unpark);
         vcpu_unpause(svc->vcpu);
     }
 
-    if ( __vcpu_on_runq(svc) )
-        __runq_remove(svc);
-
-    spin_lock_irqsave(&(prv->lock), flags);
+    spin_lock_irq(&prv->lock);
 
     if ( !list_empty(&svc->active_vcpu_elem) )
         __csched_vcpu_acct_stop_locked(prv, svc);
 
-    spin_unlock_irqrestore(&(prv->lock), flags);
+    spin_unlock_irq(&prv->lock);
 
     BUG_ON( sdom == NULL );
-    BUG_ON( !list_empty(&svc->runq_elem) );
 }
 
 static void