Re: [PATCH v1 05/12] IB/cm: Share listening CM IDs

On 13/07/2015 20:48, Jason Gunthorpe wrote:

On Mon, Jun 22, 2015 at 03:42:34PM +0300, Haggai Eran wrote:

quoted

 		spin_lock_irq(&cm.lock);
+		if (--cm_id_priv->listen_sharecount > 0) {
+			/* The id is still shared. */
+			atomic_dec(&cm_id_priv->refcount);

Nit: This looks very strange not to be cm_deref_id .. Looks OK as is
because we are sure refcount cannot be 0 here?

Yes, and because of the spin lock. But I'll change it to cm_deref_id()
so that it's more uniform.

quoted

@@ -958,8 +988,10 @@ int ib_cm_listen(struct ib_cm_id *cm_id, __be64 service_id, __be64 service_mask,
 	}
 
 	cm_id->state = IB_CM_LISTEN;
+	++cm_id_priv->listen_sharecount;

-	spin_lock_irqsave(&cm.lock, flags);
+	if (lock)
+		spin_lock_irqsave(&cm.lock, flags);

Hmm, I'd like to see the listen_sharecount consistently locked, so it
should be manipulated only while cm.lock is held..

You're right. I'll move it inside the lock.

quoted

 	if (service_id == IB_CM_ASSIGN_SERVICE_ID) {
 		cm_id->service_id = cpu_to_be64(cm.listen_service_id++);
 		cm_id->service_mask = ~cpu_to_be64(0);

@@ -968,18 +1000,98 @@ int ib_cm_listen(struct ib_cm_id *cm_id, __be64 service_id, __be64 service_mask,
 		cm_id->service_mask = service_mask;
 	}
 	cur_cm_id_priv = cm_insert_listen(cm_id_priv);
-	spin_unlock_irqrestore(&cm.lock, flags);
+	if (lock)
+		spin_unlock_irqrestore(&cm.lock, flags);
 
 	if (cur_cm_id_priv) {
 		cm_id->state = IB_CM_IDLE;
+		--cm_id_priv->listen_sharecount;

Ditto

Okay. I'll move the lock release to the end of the function.

Otherwise I don't see any other mechanical problems with this. Sean
said he was happy with the idea right?

I assume he is, since he reviewed the patch and found that
listen_sharecount leak, but he can speak for himself.

Reviewed-By: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>

Thanks.
Can I add it with the modifications above?

Haggai
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