[Xen-devel] [PATCH v4] xen: sched: fix deadlock when changing scheduling parameters

[Chong Li <lichong659@xxxxxxxxx>]

Commit f7b87b0745b4 ("enable per-VCPU parameter for RTDS") introduced
a bug: it made it possible, in Credit and Credit2, when doing domain
or vcpu parameters' manipulation, to leave the hypervisor with a
spinlock held and interrupts disabled.

Fix it.

Signed-off-by: Chong Li <chong.li@xxxxxxxxx>

Acked-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
---
CC: <dario.faggioli@xxxxxxxxxx>
CC: <george.dunlap@xxxxxxxxxxxxx>
CC: <dgolomb@xxxxxxxxxxxxxx>
CC: <mengxu@xxxxxxxxxxxxx>
CC: <jbeulich@xxxxxxxx>
CC: <lichong659@xxxxxxxxx>
---
 xen/common/sched_credit.c  | 6 ++++--
 xen/common/sched_credit2.c | 6 ++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index e5d15d8..4c4927f 100644
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -1075,6 +1075,7 @@ csched_dom_cntl(
     struct csched_dom * const sdom = CSCHED_DOM(d);
     struct csched_private *prv = CSCHED_PRIV(ops);
     unsigned long flags;
+    int rc = 0;
 
     /* Protect both get and put branches with the pluggable scheduler
      * lock. Runq lock not needed anywhere in here. */
@@ -1101,12 +1102,13 @@ csched_dom_cntl(
             sdom->cap = op->u.credit.cap;
         break;
     default:
-        return -EINVAL;
+        rc = -EINVAL;
+        break;
     }
 
     spin_unlock_irqrestore(&prv->lock, flags);
 
-    return 0;
+    return rc;
 }
 
 static inline void
diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
index d48ed5a..b8c8e40 100644
--- a/xen/common/sched_credit2.c
+++ b/xen/common/sched_credit2.c
@@ -1416,6 +1416,7 @@ csched2_dom_cntl(
     struct csched2_dom * const sdom = CSCHED2_DOM(d);
     struct csched2_private *prv = CSCHED2_PRIV(ops);
     unsigned long flags;
+    int rc = 0;
 
     /* Must hold csched2_priv lock to read and update sdom,
      * runq lock to update csvcs. */
@@ -1457,12 +1458,13 @@ csched2_dom_cntl(
         }
         break;
     default:
-        return -EINVAL;
+        rc = -EINVAL;
+        break;
     }
 
     spin_unlock_irqrestore(&prv->lock, flags);
 
-    return 0;
+    return rc;
 }
 
 static void *
-- 
1.9.1


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