Re: [PATCH 05/11] IB/cm: Share listening CM IDs

Haggai Eran
2015-06-16T12:50:39Z

On 16/06/2015 01:13, Hefty, Sean wrote:
>> @@ -722,6 +725,7 @@ struct ib_cm_id *ib_create_cm_id(struct ib_device
>> *device,
>> INIT_LIST_HEAD(&cm_id_priv->work_list);
>> atomic_set(&cm_id_priv->work_count, -1);
>> atomic_set(&cm_id_priv->refcount, 1);
>> + cm_id_priv->listen_sharecount = 1;
>
> This is setting the listen count before we know whether the cm_id will actually be used to listen.

Right. I'll move it to the new_id case in ib_cm_id_create_and_listen.

>
>
>> return &cm_id_priv->id;
>>
>> error:
>> @@ -847,11 +851,21 @@ retest:
>> spin_lock_irq(&cm_id_priv->lock);
>> switch (cm_id->state) {
>> case IB_CM_LISTEN:
>> - cm_id->state = IB_CM_IDLE;
>> spin_unlock_irq(&cm_id_priv->lock);
>> +
>> spin_lock_irq(&cm.lock);
>> + if (--cm_id_priv->listen_sharecount > 0) {
>> + /* The id is still shared. */
>> + atomic_dec(&cm_id_priv->refcount);
>> + spin_unlock_irq(&cm.lock);
>> + return;
>> + }
>> rb_erase(&cm_id_priv->service_node, &cm.listen_service_table);
>> spin_unlock_irq(&cm.lock);
>> +
>> + spin_lock_irq(&cm_id_priv->lock);
>> + cm_id->state = IB_CM_IDLE;
>> + spin_unlock_irq(&cm_id_priv->lock);
>
> Why is the state being changed? The cm_id is about to be freed anyway.

It matches the rest of the code, but I don't think it is actually being
used for listening ids. I will drop it.

>
>
>> break;
>> case IB_CM_SIDR_REQ_SENT:
>> cm_id->state = IB_CM_IDLE;
>> @@ -929,11 +943,32 @@ void ib_destroy_cm_id(struct ib_cm_id *cm_id)
>> }
>> EXPORT_SYMBOL(ib_destroy_cm_id);
>>
>> -int ib_cm_listen(struct ib_cm_id *cm_id, __be64 service_id, __be64
>> service_mask,
>> - struct ib_cm_compare_data *compare_data)
>> +/**
>> + * __ib_cm_listen - Initiates listening on the specified service ID for
>> + * connection and service ID resolution requests.
>> + * @cm_id: Connection identifier associated with the listen request.
>> + * @service_id: Service identifier matched against incoming connection
>> + * and service ID resolution requests. The service ID should be
>> specified
>> + * network-byte order. If set to IB_CM_ASSIGN_SERVICE_ID, the CM will
>> + * assign a service ID to the caller.
>> + * @service_mask: Mask applied to service ID used to listen across a
>> + * range of service IDs. If set to 0, the service ID is matched
>> + * exactly. This parameter is ignored if %service_id is set to
>> + * IB_CM_ASSIGN_SERVICE_ID.
>> + * @compare_data: This parameter is optional. It specifies data that
>> must
>> + * appear in the private data of a connection request for the specified
>> + * listen request.
>> + * @lock: If set, lock the cm.lock spin-lock when adding the id to the
>> + * listener tree. When false, the caller must already hold the spin-
>> lock,
>> + * and compare_data must be NULL.
>> + */
>> +static int __ib_cm_listen(struct ib_cm_id *cm_id, __be64 service_id,
>> + __be64 service_mask,
>> + struct ib_cm_compare_data *compare_data,
>> + bool lock)
>> {
>> struct cm_id_private *cm_id_priv, *cur_cm_id_priv;
>> - unsigned long flags;
>> + unsigned long flags = 0;
>> int ret = 0;
>>
>> service_mask = service_mask ? service_mask : ~cpu_to_be64(0);
>> @@ -959,7 +994,8 @@ int ib_cm_listen(struct ib_cm_id *cm_id, __be64
>> service_id, __be64 service_mask,
>>
>> cm_id->state = IB_CM_LISTEN;
>>
>> - spin_lock_irqsave(&cm.lock, flags);
>> + if (lock)
>> + spin_lock_irqsave(&cm.lock, flags);
>
> I'm not a fan of this sort of locking structure. Why not just move the locking into the outside calls completely? I.e. move to ib_cm_listen() instead of passing in true.

The reason is that this function can sleep when called compare_data !=
NULL, allocating the id's compare_data with GFP_KERNEL. But, since the
compare_data is going away in a later patch, I can actually fix the
locking at that point. I'll change the patch that removes compare_data
to also remove the lock parameter.

>
>
>> 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);
>> @@ -968,7 +1004,8 @@ 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;
>> @@ -978,8 +1015,86 @@ int ib_cm_listen(struct ib_cm_id *cm_id, __be64
>> service_id, __be64 service_mask,
>> }
>> return ret;
>> }
>> +
>> +int ib_cm_listen(struct ib_cm_id *cm_id, __be64 service_id, __be64
>> service_mask,
>> + struct ib_cm_compare_data *compare_data)
>> +{
>> + return __ib_cm_listen(cm_id, service_id, service_mask, compare_data,
>> + true);
>> +}
>> EXPORT_SYMBOL(ib_cm_listen);
>>
>> +/**
>> + * Create a new listening ib_cm_id and listen on the given service ID.
>> + *
>> + * If there's an existing ID listening on that same device and service
>> ID,
>> + * return it.
>> + *
>> + * @device: Device associated with the cm_id. All related communication
>> will
>> + * be associated with the specified device.
>> + * @cm_handler: Callback invoked to notify the user of CM events.
>> + * @service_id: Service identifier matched against incoming connection
>> + * and service ID resolution requests. The service ID should be
>> specified
>> + * network-byte order. If set to IB_CM_ASSIGN_SERVICE_ID, the CM will
>> + * assign a service ID to the caller.
>> + * @service_mask: Mask applied to service ID used to listen across a
>> + * range of service IDs. If set to 0, the service ID is matched
>> + * exactly. This parameter is ignored if %service_id is set to
>> + * IB_CM_ASSIGN_SERVICE_ID.
>> + *
>> + * Callers should call ib_destroy_cm_id when done with the listener ID.
>> + */
>> +struct ib_cm_id *ib_cm_id_create_and_listen(
>
> Maybe ib_cm_insert_listen() instead?

Okay.

>
>> + struct ib_device *device,
>> + ib_cm_handler cm_handler,
>> + __be64 service_id,
>> + __be64 service_mask)
>> +{
>> + struct cm_id_private *cm_id_priv;
>> + struct ib_cm_id *cm_id;
>> + unsigned long flags;
>> + int err = 0;
>> +
>> + /* Create an ID in advance, since the creation may sleep */
>> + cm_id = ib_create_cm_id(device, cm_handler, NULL);
>> + if (IS_ERR(cm_id))
>> + return cm_id;
>> +
>> + spin_lock_irqsave(&cm.lock, flags);
>> +
>> + if (service_id == IB_CM_ASSIGN_SERVICE_ID)
>> + goto new_id;
>> +
>> + /* Find an existing ID */
>> + cm_id_priv = cm_find_listen(device, service_id, NULL);
>> + if (cm_id_priv) {
>> + atomic_inc(&cm_id_priv->refcount);
>> + ++cm_id_priv->listen_sharecount;
>> + spin_unlock_irqrestore(&cm.lock, flags);
>> +
>> + ib_destroy_cm_id(cm_id);
>> + cm_id = &cm_id_priv->id;
>> + if (cm_id->cm_handler != cm_handler || cm_id->context)
>> + /* Sharing an ib_cm_id with different handlers is not
>> + * supported */
>> + return ERR_PTR(-EINVAL);
>
> This leaks listen_sharecount references.

Thanks. I'll fix that.

>
>
>> + return cm_id;
>> + }
>> +
>> +new_id:
>> + /* Use newly created ID */
>> + err = __ib_cm_listen(cm_id, service_id, service_mask, NULL, false);
>> +
>> + spin_unlock_irqrestore(&cm.lock, flags);
>> +
>> + if (err) {
>> + ib_destroy_cm_id(cm_id);
>> + return ERR_PTR(err);
>> + }
>> + return cm_id;
>> +}
>> +EXPORT_SYMBOL(ib_cm_id_create_and_listen);