svn commit: r244793 - in user/attilio/membarclean/dev: drm drm2 netmap virtio

[Attilio Rao]

Author: attilio
Date: Fri Dec 28 22:18:41 2012
New Revision: 244793
URL: http://svnweb.freebsd.org/changeset/base/244793

Log:
  - Remove rmb() usage from netmap and replace it with intended operation
    to do actual memory fetching reads.
  - GC unused DRM_WRITEMEMORYBARRIER() from drm and drm2.
  - Use atomic_load_acq_*() in virtio and drm2 in places that don't need
    to use rmb().
  
  All these changes remove completely rmb() from MI code, with the
  exception of cxgbe which will be hammered in a followup commit.

Modified:
  user/attilio/membarclean/dev/drm/drmP.h
  user/attilio/membarclean/dev/drm2/drmP.h
  user/attilio/membarclean/dev/drm2/drm_atomic.h
  user/attilio/membarclean/dev/drm2/drm_irq.c
  user/attilio/membarclean/dev/netmap/netmap.c
  user/attilio/membarclean/dev/virtio/virtqueue.c

Modified: user/attilio/membarclean/dev/drm/drmP.h
==============================================================================
--- user/attilio/membarclean/dev/drm/drmP.h	Fri Dec 28 22:06:50 2012	(r244792)
+++ user/attilio/membarclean/dev/drm/drmP.h	Fri Dec 28 22:18:41 2012	(r244793)
@@ -241,11 +241,9 @@ typedef u_int32_t u32;
 typedef u_int16_t u16;
 typedef u_int8_t u8;
 
-/* DRM_READMEMORYBARRIER() prevents reordering of reads.
- * DRM_WRITEMEMORYBARRIER() prevents reordering of writes.
+/* DRM_WRITEMEMORYBARRIER() prevents reordering of writes.
  * DRM_MEMORYBARRIER() prevents reordering of reads and writes.
  */
-#define DRM_READMEMORYBARRIER()		rmb()
 #define DRM_WRITEMEMORYBARRIER()	wmb()
 #define DRM_MEMORYBARRIER()		mb()
 

Modified: user/attilio/membarclean/dev/drm2/drmP.h
==============================================================================
--- user/attilio/membarclean/dev/drm2/drmP.h	Fri Dec 28 22:06:50 2012	(r244792)
+++ user/attilio/membarclean/dev/drm2/drmP.h	Fri Dec 28 22:18:41 2012	(r244793)
@@ -263,11 +263,9 @@ typedef int32_t s32;
 typedef int16_t s16;
 typedef int8_t s8;
 
-/* DRM_READMEMORYBARRIER() prevents reordering of reads.
- * DRM_WRITEMEMORYBARRIER() prevents reordering of writes.
+/* DRM_WRITEMEMORYBARRIER() prevents reordering of writes.
  * DRM_MEMORYBARRIER() prevents reordering of reads and writes.
  */
-#define DRM_READMEMORYBARRIER()		rmb()
 #define DRM_WRITEMEMORYBARRIER()	wmb()
 #define DRM_MEMORYBARRIER()		mb()
 

Modified: user/attilio/membarclean/dev/drm2/drm_atomic.h
==============================================================================
--- user/attilio/membarclean/dev/drm2/drm_atomic.h	Fri Dec 28 22:06:50 2012	(r244792)
+++ user/attilio/membarclean/dev/drm2/drm_atomic.h	Fri Dec 28 22:18:41 2012	(r244793)
@@ -38,6 +38,7 @@ typedef u_int32_t atomic_t;
 
 #define atomic_set(p, v)	(*(p) = (v))
 #define atomic_read(p)		(*(p))
+#define atomic_read_acq(p)	atomic_load_acq_int(p)
 #define atomic_inc(p)		atomic_add_int(p, 1)
 #define atomic_dec(p)		atomic_subtract_int(p, 1)
 #define atomic_add(n, p)	atomic_add_int(p, n)

Modified: user/attilio/membarclean/dev/drm2/drm_irq.c
==============================================================================
--- user/attilio/membarclean/dev/drm2/drm_irq.c	Fri Dec 28 22:06:50 2012	(r244792)
+++ user/attilio/membarclean/dev/drm2/drm_irq.c	Fri Dec 28 22:18:41 2012	(r244793)
@@ -701,8 +701,7 @@ u32 drm_vblank_count_and_time(struct drm
 	do {
 		cur_vblank = atomic_read(&dev->_vblank_count[crtc]);
 		*vblanktime = vblanktimestamp(dev, crtc, cur_vblank);
-		rmb();
-	} while (cur_vblank != atomic_read(&dev->_vblank_count[crtc]));
+	} while (cur_vblank != atomic_read_acq(&dev->_vblank_count[crtc]));
 
 	return cur_vblank;
 }

Modified: user/attilio/membarclean/dev/netmap/netmap.c
==============================================================================
--- user/attilio/membarclean/dev/netmap/netmap.c	Fri Dec 28 22:06:50 2012	(r244792)
+++ user/attilio/membarclean/dev/netmap/netmap.c	Fri Dec 28 22:18:41 2012	(r244793)
@@ -98,6 +98,9 @@ MALLOC_DEFINE(M_NETMAP, "netmap", "Netwo
 #include <net/netmap.h>
 #include <dev/netmap/netmap_kern.h>
 
+#define	MEMFETCH(var)							\
+	(__DEVOLATILE(__typeof(var), *((volatile __typeof(var) *)&var)))
+
 u_int netmap_total_buffers;
 u_int netmap_buf_size;
 char *netmap_buffer_base;	/* address of an invalid buffer */
@@ -1081,10 +1084,7 @@ error:
 			error = ENXIO;
 			break;
 		}
-		rmb(); /* make sure following reads are not from cache */
-
-
-		ifp = priv->np_ifp;	/* we have a reference */
+		ifp = MEMFETCH(priv->np_ifp);
 
 		if (ifp == NULL) {
 			D("Internal error: nifp != NULL && ifp == NULL");
@@ -1194,9 +1194,7 @@ netmap_poll(struct cdev *dev, int events
 		D("No if registered");
 		return POLLERR;
 	}
-	rmb(); /* make sure following reads are not from cache */
-
-	ifp = priv->np_ifp;
+	ifp = MEMFETCH(priv->np_ifp);
 	// XXX check for deleting() ?
 	if ( (ifp->if_capenable & IFCAP_NETMAP) == 0)
 		return POLLERR;

Modified: user/attilio/membarclean/dev/virtio/virtqueue.c
==============================================================================
--- user/attilio/membarclean/dev/virtio/virtqueue.c	Fri Dec 28 22:06:50 2012	(r244792)
+++ user/attilio/membarclean/dev/virtio/virtqueue.c	Fri Dec 28 22:18:41 2012	(r244793)
@@ -525,8 +525,7 @@ virtqueue_dequeue(struct virtqueue *vq, 
 	used_idx = vq->vq_used_cons_idx++ & (vq->vq_nentries - 1);
 	uep = &vq->vq_ring.used->ring[used_idx];
 
-	rmb();
-	desc_idx = (uint16_t) uep->id;
+	desc_idx = (uint16_t)atomic_load_acq_32(&uep->id);
 	if (len != NULL)
 		*len = uep->len;