[openib-general] libmthca: make fence work

[Roland Dreier]

I fixed this in a slightly different way that seemed cleaner to me
(see below).  Please verify that my fix works for you.

Thanks,
  Roland

Index: libmthca/src/qp.c
===================================================================
--- libmthca/src/qp.c	(revision 8875)
+++ libmthca/src/qp.c	(working copy)
@@ -46,6 +46,10 @@
 #include "doorbell.h"
 #include "wqe.h"
 
+enum {
+	MTHCA_SEND_DOORBELL_FENCE = 1 << 5
+};
+
 static const uint8_t mthca_opcode[] = {
 	[IBV_WR_SEND]                 = MTHCA_OPCODE_SEND,
 	[IBV_WR_SEND_WITH_IMM]        = MTHCA_OPCODE_SEND_IMM,
@@ -104,9 +108,18 @@ int mthca_tavor_post_send(struct ibv_qp 
 	int ind;
 	int nreq;
 	int ret = 0;
-	int size, size0 = 0;
+	int size;
+	int size0 = 0;
 	int i;
-	uint32_t f0 = 0, op0 = 0;
+	/*
+	 * f0 and op0 cannot be used unless nreq > 0, which means this
+	 * function makes it through the loop at least once.  So the
+	 * code inside the if (!size0) will be executed, and f0 and
+	 * op0 will be initialized.  So any gcc warning about "may be
+	 * used unitialized" is bogus.
+	 */
+	uint32_t f0;
+	uint32_t op0;
 
 	pthread_spin_lock(&qp->sq.lock);
 
@@ -290,6 +303,8 @@ int mthca_tavor_post_send(struct ibv_qp 
 		if (!size0) {
 			size0 = size;
 			op0   = mthca_opcode[wr->opcode];
+			f0    = wr->send_flags & IBV_SEND_FENCE ?
+				MTHCA_SEND_DOORBELL_FENCE : 0;
 		}
 
 		++ind;
@@ -434,9 +449,18 @@ int mthca_arbel_post_send(struct ibv_qp 
 	int ind;
 	int nreq;
 	int ret = 0;
-	int size, size0 = 0;
+	int size;
+	int size0 = 0;
 	int i;
-	uint32_t f0 = 0, op0 = 0;
+	/*
+	 * f0 and op0 cannot be used unless nreq > 0, which means this
+	 * function makes it through the loop at least once.  So the
+	 * code inside the if (!size0) will be executed, and f0 and
+	 * op0 will be initialized.  So any gcc warning about "may be
+	 * used unitialized" is bogus.
+	 */
+	uint32_t f0;
+	uint32_t op0;
 
 	pthread_spin_lock(&qp->sq.lock);
 
@@ -644,6 +668,8 @@ int mthca_arbel_post_send(struct ibv_qp 
 		if (!size0) {
 			size0 = size;
 			op0   = mthca_opcode[wr->opcode];
+			f0    = wr->send_flags & IBV_SEND_FENCE ?
+				MTHCA_SEND_DOORBELL_FENCE : 0;
 		}
 
 		++ind;
Index: libmthca/ChangeLog
===================================================================
--- libmthca/ChangeLog	(revision 8875)
+++ libmthca/ChangeLog	(working copy)
@@ -1,3 +1,8 @@
+2006-08-09  Michael S. Tsirkin  <mst at mellanox.co.il>
+
+	* src/qp.c (mthca_tavor_post_send, mthca_arbel_post_send): Fence
+	bit must be set in both doorbell and WQE.
+
 2006-08-03  Jack Morgenstein  <jackm at mellanox.co.il>
 
 	* src/mthca.h: Include <stddef.h> to get definition of offsetof().