Merge pull request #6212 from ooststep/creditfc_fix

prov/verbs: account for off-by-one credit initialization
ofiwg · Aug 26, 2020 · 220af33 · 220af33
2 parents b3de148 + 8018cd1
commit 220af33
Show file tree

Hide file tree

Showing 2 changed files with 7 additions and 1 deletion.
diff --git a/prov/verbs/src/fi_verbs.h b/prov/verbs/src/fi_verbs.h
@@ -569,7 +569,7 @@ struct vrb_ep {
 	uint64_t			sq_credits;
 	uint64_t			peer_rq_credits;
 	/* Protected by recv CQ lock */
-	uint64_t			rq_credits_avail;
+	int64_t				rq_credits_avail;
 	uint64_t			threshold;
 
 	union {

diff --git a/prov/verbs/src/verbs_ep.c b/prov/verbs/src/verbs_ep.c
@@ -315,6 +315,12 @@ vrb_alloc_init_ep(struct fi_info *info, struct vrb_domain *domain,
 			return NULL;
 	}
 
+	// When we are enabling flow control, we artificially inject
+	// a credit so that the credit messaging itself is not blocked
+	// by a lack of credits.  To counter this, we will adjust the number
+	// of credit we send the first time by initializing to -1.
+	ep->rq_credits_avail = -1;
+
 	ep->info = fi_dupinfo(info);
 	if (!ep->info)
 		goto err1;