Re: [openib-general] [PATCH 5/6] iser RDMA CM (CMA) and IB verbsinteraction

[Or Gerlitz]

Or Gerlitz wrote:
> Sean Hefty wrote:
> > > +static void iser_disconnected_handler(struct rdma_cm_id *cma_id)
> > > +{
> > > +    struct iser_conn *ib_conn;
> > > +
> > > +    ib_conn = (struct iser_conn *)cma_id->context;
> > > +    ib_conn->disc_evt_flag = 1;
> > > +
> > > +    /* If this event is unsolicited this means that the conn is 
> > > being */
> > > +    /* terminated asynchronously from the iSCSI layer's 
> > > perspective.  */
> > > +    if (atomic_read(&ib_conn->state) == ISER_CONN_PENDING) {
> > > +        atomic_set(&ib_conn->state, ISER_CONN_DOWN);
> > > +        wake_up_interruptible(&ib_conn->wait);
> > > +    } else {
> > > +        if (atomic_read(&ib_conn->state) == ISER_CONN_UP) {
> > > +            atomic_set(&ib_conn->state, ISER_CONN_TERMINATING);
> > > +            iscsi_conn_failure(ib_conn->iser_conn->iscsi_conn,
> > > +                        ISCSI_ERR_CONN_FAILED);
> > > +        }
> > > +        /* Complete the termination process if no posts are pending */
> > > +        if ((atomic_read(&ib_conn->post_recv_buf_count) == 0) &&
> > > +            (atomic_read(&ib_conn->post_send_buf_count) == 0)) {
> > > +            atomic_set(&ib_conn->state, ISER_CONN_DOWN);
> > > +            wake_up_interruptible(&ib_conn->wait);
> > > +        }
> > > +    }

> > Are there races here between reading ib_conn->state and setting it?  
> > Could it have changed in between the atomic_read() and atomic_set()?

> It seems that indeed a race is possible here, i am rethinking now on the 
> implementation of the ib connection states moves, thanks for pointing this.

Following a review and the clarification i have got from you re cma 
callbacks serialization, i have committed this change which removes 
unneeded state checks from two flows (disconnect handler and connect error)

Or.

r6900 | ogerlitz | 2006-05-04 11:06:24 +0300 (Thu, 04 May 2006) | 7 lines

two fixes to iser ib conn state management:

+1 when getting DISCONNECTED cma event, iser's state can't be PENDING
+2 when connect_error is called, iser's state is PENDING, no need to 
check it

Signed-off-by: Or Gerlitz <ogerlitz@xxxxxxxxxxxx

Index: iser_verbs.c
===================================================================
--- iser_verbs.c	(revision 6802)
+++ iser_verbs.c	(revision 6900)
@@ -309,12 +309,8 @@ static void iser_connect_error(struct rd
 	struct iser_conn *ib_conn;
 	ib_conn = (struct iser_conn *)cma_id->context;

-	if (atomic_read(&ib_conn->state) == ISER_CONN_PENDING) {
-		atomic_set(&ib_conn->state, ISER_CONN_DOWN);
-		wake_up_interruptible(&ib_conn->wait);
-	} else
-		iser_err("Unexpected evt for conn.state: %d\n",
-			 atomic_read(&ib_conn->state));
+	atomic_set(&ib_conn->state, ISER_CONN_DOWN);
+	wake_up_interruptible(&ib_conn->wait);
 }

 static void iser_addr_handler(struct rdma_cm_id *cma_id)
@@ -386,21 +382,16 @@ static void iser_disconnected_handler(st

 	/* If this event is unsolicited this means that the conn is being */
 	/* terminated asynchronously from the iSCSI layer's perspective.  */
-	if (atomic_read(&ib_conn->state) == ISER_CONN_PENDING) {
+	if (atomic_read(&ib_conn->state) == ISER_CONN_UP) {
+		atomic_set(&ib_conn->state, ISER_CONN_TERMINATING);
+		iscsi_conn_failure(ib_conn->iser_conn->iscsi_conn,
+				   ISCSI_ERR_CONN_FAILED);
+	}
+	/* Complete the termination process if no posts are pending */
+	if ((atomic_read(&ib_conn->post_recv_buf_count) == 0) &&
+	    (atomic_read(&ib_conn->post_send_buf_count) == 0)) {
 		atomic_set(&ib_conn->state, ISER_CONN_DOWN);
 		wake_up_interruptible(&ib_conn->wait);
-	} else {
-		if (atomic_read(&ib_conn->state) == ISER_CONN_UP) {
-			atomic_set(&ib_conn->state, ISER_CONN_TERMINATING);
-			iscsi_conn_failure(ib_conn->iser_conn->iscsi_conn,
-						ISCSI_ERR_CONN_FAILED);
-		}
-		/* Complete the termination process if no posts are pending */
-		if ((atomic_read(&ib_conn->post_recv_buf_count) == 0) &&
-		    (atomic_read(&ib_conn->post_send_buf_count) == 0)) {
-			atomic_set(&ib_conn->state, ISER_CONN_DOWN);
-			wake_up_interruptible(&ib_conn->wait);
-		}
 	}
 }


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