[Xen-changelog] [xen staging] xen/vm-event: Expand vm_event_* spinlock macros and rename the lock

[patchbot@xxxxxxx]

commit a63f8f0672e6b9582f32b4ac61a595e5aea7ede7
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri May 31 13:57:03 2019 -0700
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Jun 4 14:43:51 2019 +0100

    xen/vm-event: Expand vm_event_* spinlock macros and rename the lock
    
    These serve no purpose, but to add to the congnitive load of following
    the code.  Remove the level of indirection.
    
    Furthermore, the lock protects all data in vm_event_domain, making
    ring_lock a poor choice of name.
    
    For vm_event_get_response() and vm_event_grab_slot(), fold the exit
    paths to have a single unlock, as the compiler can't make this
    optimisation itself.
    
    No functional change.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
---
 xen/common/vm_event.c   | 58 ++++++++++++++++++++++++-------------------------
 xen/include/xen/sched.h |  3 +--
 2 files changed, 30 insertions(+), 31 deletions(-)

diff --git a/xen/common/vm_event.c b/xen/common/vm_event.c
index 902e152e21..db975e9eeb 100644
--- a/xen/common/vm_event.c
+++ b/xen/common/vm_event.c
@@ -35,10 +35,6 @@
 #define xen_rmb()  smp_rmb()
 #define xen_wmb()  smp_wmb()
 
-#define vm_event_ring_lock_init(_ved)  spin_lock_init(&(_ved)->ring_lock)
-#define vm_event_ring_lock(_ved)       spin_lock(&(_ved)->ring_lock)
-#define vm_event_ring_unlock(_ved)     spin_unlock(&(_ved)->ring_lock)
-
 static int vm_event_enable(
     struct domain *d,
     struct xen_domctl_vm_event_op *vec,
@@ -66,8 +62,8 @@ static int vm_event_enable(
     if ( ring_gfn == 0 )
         return -EOPNOTSUPP;
 
-    vm_event_ring_lock_init(*ved);
-    vm_event_ring_lock(*ved);
+    spin_lock_init(&(*ved)->lock);
+    spin_lock(&(*ved)->lock);
 
     rc = vm_event_init_domain(d);
 
@@ -101,13 +97,13 @@ static int vm_event_enable(
     /* Initialize the last-chance wait queue. */
     init_waitqueue_head(&(*ved)->wq);
 
-    vm_event_ring_unlock(*ved);
+    spin_unlock(&(*ved)->lock);
     return 0;
 
  err:
     destroy_ring_for_helper(&(*ved)->ring_page,
                             (*ved)->ring_pg_struct);
-    vm_event_ring_unlock(*ved);
+    spin_unlock(&(*ved)->lock);
     xfree(*ved);
     *ved = NULL;
 
@@ -200,11 +196,11 @@ static int vm_event_disable(struct domain *d, struct 
vm_event_domain **ved)
     {
         struct vcpu *v;
 
-        vm_event_ring_lock(*ved);
+        spin_lock(&(*ved)->lock);
 
         if ( !list_empty(&(*ved)->wq.list) )
         {
-            vm_event_ring_unlock(*ved);
+            spin_unlock(&(*ved)->lock);
             return -EBUSY;
         }
 
@@ -226,7 +222,7 @@ static int vm_event_disable(struct domain *d, struct 
vm_event_domain **ved)
 
         vm_event_cleanup_domain(d);
 
-        vm_event_ring_unlock(*ved);
+        spin_unlock(&(*ved)->lock);
     }
 
     xfree(*ved);
@@ -292,7 +288,7 @@ void vm_event_put_request(struct domain *d,
 
     req->version = VM_EVENT_INTERFACE_VERSION;
 
-    vm_event_ring_lock(ved);
+    spin_lock(&ved->lock);
 
     /* Due to the reservations, this step must succeed. */
     front_ring = &ved->front_ring;
@@ -319,7 +315,7 @@ void vm_event_put_request(struct domain *d,
         !atomic_read(&curr->vm_event_pause_count) )
         vm_event_mark_and_pause(curr, ved);
 
-    vm_event_ring_unlock(ved);
+    spin_unlock(&ved->lock);
 
     notify_via_xen_event_channel(d, ved->xen_port);
 }
@@ -329,17 +325,15 @@ static int vm_event_get_response(struct domain *d, struct 
vm_event_domain *ved,
 {
     vm_event_front_ring_t *front_ring;
     RING_IDX rsp_cons;
+    int rc = 0;
 
-    vm_event_ring_lock(ved);
+    spin_lock(&ved->lock);
 
     front_ring = &ved->front_ring;
     rsp_cons = front_ring->rsp_cons;
 
     if ( !RING_HAS_UNCONSUMED_RESPONSES(front_ring) )
-    {
-        vm_event_ring_unlock(ved);
-        return 0;
-    }
+        goto out;
 
     /* Copy response */
     memcpy(rsp, RING_GET_RESPONSE(front_ring, rsp_cons), sizeof(*rsp));
@@ -353,9 +347,12 @@ static int vm_event_get_response(struct domain *d, struct 
vm_event_domain *ved,
      * there may be additional space available in the ring. */
     vm_event_wake(d, ved);
 
-    vm_event_ring_unlock(ved);
+    rc = 1;
 
-    return 1;
+ out:
+    spin_unlock(&ved->lock);
+
+    return rc;
 }
 
 /*
@@ -455,35 +452,38 @@ void vm_event_cancel_slot(struct domain *d, struct 
vm_event_domain *ved)
     if( !vm_event_check_ring(ved) )
         return;
 
-    vm_event_ring_lock(ved);
+    spin_lock(&ved->lock);
     vm_event_release_slot(d, ved);
-    vm_event_ring_unlock(ved);
+    spin_unlock(&ved->lock);
 }
 
 static int vm_event_grab_slot(struct vm_event_domain *ved, int foreign)
 {
     unsigned int avail_req;
+    int rc;
 
     if ( !ved->ring_page )
         return -EOPNOTSUPP;
 
-    vm_event_ring_lock(ved);
+    spin_lock(&ved->lock);
 
     avail_req = vm_event_ring_available(ved);
+
+    rc = -EBUSY;
     if ( avail_req == 0 )
-    {
-        vm_event_ring_unlock(ved);
-        return -EBUSY;
-    }
+        goto out;
 
     if ( !foreign )
         ved->target_producers++;
     else
         ved->foreign_producers++;
 
-    vm_event_ring_unlock(ved);
+    rc = 0;
 
-    return 0;
+ out:
+    spin_unlock(&ved->lock);
+
+    return rc;
 }
 
 /* Simple try_grab wrapper for use in the wait_event() macro. */
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 2201faca6b..b9691fc96e 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -282,8 +282,7 @@ struct vcpu
 /* VM event */
 struct vm_event_domain
 {
-    /* ring lock */
-    spinlock_t ring_lock;
+    spinlock_t lock;
     /* The ring has 64 entries */
     unsigned char foreign_producers;
     unsigned char target_producers;
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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