sched_rt: serialize vcpu data access

Fix the following two issues in rtds scheduler:
1) The runq queue lock is not grabbed when rt_update_deadline is
called in rt_alloc_vdata function, which may cause race condition;
Solution: Move call to rt_update_deadline from _alloc to _insert;
Note: rt_alloc_vdata does not need grab the runq lock, because only one
cpu will allocate the rt_vcpu; before the rt_vcpu is inserted into the
runq, no more than one cpu operates on the rt_vcpu.

2) rt_vcpu_remove should grab the runq lock before remove the vcpu
from runq; otherwise, race condition may happen.
Solution: Add lock in rt_vcpu_remove().

Reported-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Meng Xu <mengxu@cis.upenn.edu>
Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com>
Reviewed-by: George Dunlap <george.dunlap@eu.citrix.com>
Release-Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
index 8251e41cfb1097051529856a292ec420a0c50fdd..e70d6c733f7670cf148097233acde0776c736290 100644 (file)
--- a/xen/common/sched_rt.c
+++ b/xen/common/sched_rt.c
@@ -508,7 +508,6 @@ static void *
 rt_alloc_vdata(const struct scheduler *ops, struct vcpu *vc, void *dd)
 {
     struct rt_vcpu *svc;
-    s_time_t now = NOW();
 
     /* Allocate per-VCPU info */
     svc = xzalloc(struct rt_vcpu);
@@ -526,10 +525,6 @@ rt_alloc_vdata(const struct scheduler *ops, struct vcpu *vc, void *dd)
     if ( !is_idle_vcpu(vc) )
         svc->budget = RTDS_DEFAULT_BUDGET;
 
-    ASSERT( now >= svc->cur_deadline );
-
-    rt_update_deadline(now, svc);
-
     return svc;
 }
 
@@ -552,11 +547,15 @@ static void
 rt_vcpu_insert(const struct scheduler *ops, struct vcpu *vc)
 {
     struct rt_vcpu *svc = rt_vcpu(vc);
+    s_time_t now = NOW();
 
     /* not addlocate idle vcpu to dom vcpu list */
     if ( is_idle_vcpu(vc) )
         return;
 
+    if ( now >= svc->cur_deadline )
+        rt_update_deadline(now, svc);
+
     if ( !__vcpu_on_q(svc) && vcpu_runnable(vc) && !vc->is_running )
         __runq_insert(ops, svc);
 
@@ -573,11 +572,14 @@ rt_vcpu_remove(const struct scheduler *ops, struct vcpu *vc)
 {
     struct rt_vcpu * const svc = rt_vcpu(vc);
     struct rt_dom * const sdom = svc->sdom;
+    spinlock_t *lock;
 
     BUG_ON( sdom == NULL );
 
+    lock = vcpu_schedule_lock_irq(vc);
     if ( __vcpu_on_q(svc) )
         __q_remove(svc);
+    vcpu_schedule_unlock_irq(lock, vc);
 
     if ( !is_idle_vcpu(vc) )
         list_del_init(&svc->sdom_elem);