[Xen-changelog] [xen master] sched: fix locking of remove_vcpu() in credit1

[patchbot@xxxxxxx]

commit 897cc6d07acd3e66356f021c5f7f9a49ef061d5d
Author:     Dario Faggioli <dario.faggioli@xxxxxxxxxx>
AuthorDate: Fri Nov 6 15:16:38 2015 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Nov 6 15:16:38 2015 +0100

    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@xxxxxxxxxx>
    Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>
---
 xen/common/sched_credit.c |   11 ++++-------
 1 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index 9eb457c..72a2109 100644
--- 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
--
generated by git-patchbot for /home/xen/git/xen.git#master

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