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author | Jason Gunthorpe <jgg@mellanox.com> | 2020-03-10 11:25:38 +0200 |
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committer | Jason Gunthorpe <jgg@mellanox.com> | 2020-03-17 17:05:52 -0300 |
commit | c206f8bad15d30f1e35821c21a2fb146e4668ebf (patch) | |
tree | c4e8739ec6b8d3bb751842beabcbbecfbb2017b0 /drivers/infiniband/core | |
parent | 083bfdbfd5ee2d008d256975d962ef75ddbbc353 (diff) | |
download | linux-c206f8bad15d30f1e35821c21a2fb146e4668ebf.tar.gz linux-c206f8bad15d30f1e35821c21a2fb146e4668ebf.tar.bz2 linux-c206f8bad15d30f1e35821c21a2fb146e4668ebf.zip |
RDMA/cm: Make it clearer how concurrency works in cm_req_handler()
ib_crate_cm_id() immediately places the id in the xarray, and publishes it
into the remote_id and remote_qpn rbtrees. This makes it visible to other
threads before it is fully set up.
It appears the thinking here was that the states IB_CM_IDLE and
IB_CM_REQ_RCVD do not allow any MAD handler or lookup in the remote_id and
remote_qpn rbtrees to advance.
However, cm_rej_handler() does take an action on IB_CM_REQ_RCVD, which is
not really expected by the design.
Make the whole thing clearer:
- Keep the new cm_id out of the xarray until it is completely set up.
This directly prevents MAD handlers and all rbtree lookups from seeing
the pointer.
- Move all the trivial setup right to the top so it is obviously done
before any concurrency begins
- Move the mutation of the cm_id_priv out of cm_match_id() and into the
caller so the state transition is obvious
- Place the manipulation of the work_list at the end, under lock, after
the cm_id is placed in the xarray. The work_count cannot change on an
ID outside the xarray.
- Add some comments
Link: https://lore.kernel.org/r/20200310092545.251365-9-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Diffstat (limited to 'drivers/infiniband/core')
-rw-r--r-- | drivers/infiniband/core/cm.c | 99 |
1 files changed, 57 insertions, 42 deletions
diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c index 36e7ce522d04..3f125044d35e 100644 --- a/drivers/infiniband/core/cm.c +++ b/drivers/infiniband/core/cm.c @@ -1958,14 +1958,10 @@ static struct cm_id_private * cm_match_req(struct cm_work *work, cm_issue_rej(work->port, work->mad_recv_wc, IB_CM_REJ_INVALID_SERVICE_ID, CM_MSG_RESPONSE_REQ, NULL, 0); - goto out; + return NULL; } refcount_inc(&listen_cm_id_priv->refcount); - refcount_inc(&cm_id_priv->refcount); - cm_id_priv->id.state = IB_CM_REQ_RCVD; - atomic_inc(&cm_id_priv->work_count); spin_unlock_irq(&cm.lock); -out: return listen_cm_id_priv; } @@ -2007,7 +2003,6 @@ static void cm_process_routed_req(struct cm_req_msg *req_msg, struct ib_wc *wc) static int cm_req_handler(struct cm_work *work) { - struct ib_cm_id *cm_id; struct cm_id_private *cm_id_priv, *listen_cm_id_priv; struct cm_req_msg *req_msg; const struct ib_global_route *grh; @@ -2016,13 +2011,33 @@ static int cm_req_handler(struct cm_work *work) req_msg = (struct cm_req_msg *)work->mad_recv_wc->recv_buf.mad; - cm_id = ib_create_cm_id(work->port->cm_dev->ib_device, NULL, NULL); - if (IS_ERR(cm_id)) - return PTR_ERR(cm_id); + cm_id_priv = + cm_alloc_id_priv(work->port->cm_dev->ib_device, NULL, NULL); + if (IS_ERR(cm_id_priv)) + return PTR_ERR(cm_id_priv); - cm_id_priv = container_of(cm_id, struct cm_id_private, id); cm_id_priv->id.remote_id = cpu_to_be32(IBA_GET(CM_REQ_LOCAL_COMM_ID, req_msg)); + cm_id_priv->id.service_id = + cpu_to_be64(IBA_GET(CM_REQ_SERVICE_ID, req_msg)); + cm_id_priv->id.service_mask = ~cpu_to_be64(0); + cm_id_priv->tid = req_msg->hdr.tid; + cm_id_priv->timeout_ms = cm_convert_to_ms( + IBA_GET(CM_REQ_LOCAL_CM_RESPONSE_TIMEOUT, req_msg)); + cm_id_priv->max_cm_retries = IBA_GET(CM_REQ_MAX_CM_RETRIES, req_msg); + cm_id_priv->remote_qpn = + cpu_to_be32(IBA_GET(CM_REQ_LOCAL_QPN, req_msg)); + cm_id_priv->initiator_depth = + IBA_GET(CM_REQ_RESPONDER_RESOURCES, req_msg); + cm_id_priv->responder_resources = + IBA_GET(CM_REQ_INITIATOR_DEPTH, req_msg); + cm_id_priv->path_mtu = IBA_GET(CM_REQ_PATH_PACKET_PAYLOAD_MTU, req_msg); + cm_id_priv->pkey = cpu_to_be16(IBA_GET(CM_REQ_PARTITION_KEY, req_msg)); + cm_id_priv->sq_psn = cpu_to_be32(IBA_GET(CM_REQ_STARTING_PSN, req_msg)); + cm_id_priv->retry_count = IBA_GET(CM_REQ_RETRY_COUNT, req_msg); + cm_id_priv->rnr_retry_count = IBA_GET(CM_REQ_RNR_RETRY_COUNT, req_msg); + cm_id_priv->qp_type = cm_req_get_qp_type(req_msg); + ret = cm_init_av_for_response(work->port, work->mad_recv_wc->wc, work->mad_recv_wc->recv_buf.grh, &cm_id_priv->av); @@ -2034,27 +2049,26 @@ static int cm_req_handler(struct cm_work *work) ret = PTR_ERR(cm_id_priv->timewait_info); goto destroy; } - cm_id_priv->timewait_info->work.remote_id = - cpu_to_be32(IBA_GET(CM_REQ_LOCAL_COMM_ID, req_msg)); + cm_id_priv->timewait_info->work.remote_id = cm_id_priv->id.remote_id; cm_id_priv->timewait_info->remote_ca_guid = cpu_to_be64(IBA_GET(CM_REQ_LOCAL_CA_GUID, req_msg)); - cm_id_priv->timewait_info->remote_qpn = - cpu_to_be32(IBA_GET(CM_REQ_LOCAL_QPN, req_msg)); + cm_id_priv->timewait_info->remote_qpn = cm_id_priv->remote_qpn; + + /* + * Note that the ID pointer is not in the xarray at this point, + * so this set is only visible to the local thread. + */ + cm_id_priv->id.state = IB_CM_REQ_RCVD; listen_cm_id_priv = cm_match_req(work, cm_id_priv); if (!listen_cm_id_priv) { pr_debug("%s: local_id %d, no listen_cm_id_priv\n", __func__, - be32_to_cpu(cm_id->local_id)); + be32_to_cpu(cm_id_priv->id.local_id)); + cm_id_priv->id.state = IB_CM_IDLE; ret = -EINVAL; goto destroy; } - cm_id_priv->id.cm_handler = listen_cm_id_priv->id.cm_handler; - cm_id_priv->id.context = listen_cm_id_priv->id.context; - cm_id_priv->id.service_id = - cpu_to_be64(IBA_GET(CM_REQ_SERVICE_ID, req_msg)); - cm_id_priv->id.service_mask = ~cpu_to_be64(0); - cm_process_routed_req(req_msg, work->mad_recv_wc->wc); memset(&work->path[0], 0, sizeof(work->path[0])); @@ -2092,10 +2106,10 @@ static int cm_req_handler(struct cm_work *work) work->port->port_num, 0, &work->path[0].sgid); if (err) - ib_send_cm_rej(cm_id, IB_CM_REJ_INVALID_GID, + ib_send_cm_rej(&cm_id_priv->id, IB_CM_REJ_INVALID_GID, NULL, 0, NULL, 0); else - ib_send_cm_rej(cm_id, IB_CM_REJ_INVALID_GID, + ib_send_cm_rej(&cm_id_priv->id, IB_CM_REJ_INVALID_GID, &work->path[0].sgid, sizeof(work->path[0].sgid), NULL, 0); @@ -2105,39 +2119,40 @@ static int cm_req_handler(struct cm_work *work) ret = cm_init_av_by_path(&work->path[1], NULL, &cm_id_priv->alt_av, cm_id_priv); if (ret) { - ib_send_cm_rej(cm_id, IB_CM_REJ_INVALID_ALT_GID, + ib_send_cm_rej(&cm_id_priv->id, + IB_CM_REJ_INVALID_ALT_GID, &work->path[0].sgid, sizeof(work->path[0].sgid), NULL, 0); goto rejected; } } - cm_id_priv->tid = req_msg->hdr.tid; - cm_id_priv->timeout_ms = cm_convert_to_ms( - IBA_GET(CM_REQ_LOCAL_CM_RESPONSE_TIMEOUT, req_msg)); - cm_id_priv->max_cm_retries = IBA_GET(CM_REQ_MAX_CM_RETRIES, req_msg); - cm_id_priv->remote_qpn = - cpu_to_be32(IBA_GET(CM_REQ_LOCAL_QPN, req_msg)); - cm_id_priv->initiator_depth = - IBA_GET(CM_REQ_RESPONDER_RESOURCES, req_msg); - cm_id_priv->responder_resources = - IBA_GET(CM_REQ_INITIATOR_DEPTH, req_msg); - cm_id_priv->path_mtu = IBA_GET(CM_REQ_PATH_PACKET_PAYLOAD_MTU, req_msg); - cm_id_priv->pkey = cpu_to_be16(IBA_GET(CM_REQ_PARTITION_KEY, req_msg)); - cm_id_priv->sq_psn = cpu_to_be32(IBA_GET(CM_REQ_STARTING_PSN, req_msg)); - cm_id_priv->retry_count = IBA_GET(CM_REQ_RETRY_COUNT, req_msg); - cm_id_priv->rnr_retry_count = IBA_GET(CM_REQ_RNR_RETRY_COUNT, req_msg); - cm_id_priv->qp_type = cm_req_get_qp_type(req_msg); + cm_id_priv->id.cm_handler = listen_cm_id_priv->id.cm_handler; + cm_id_priv->id.context = listen_cm_id_priv->id.context; cm_format_req_event(work, cm_id_priv, &listen_cm_id_priv->id); + + /* Now MAD handlers can see the new ID */ + spin_lock_irq(&cm_id_priv->lock); + cm_finalize_id(cm_id_priv); + + /* Refcount belongs to the event, pairs with cm_process_work() */ + refcount_inc(&cm_id_priv->refcount); + atomic_inc(&cm_id_priv->work_count); + spin_unlock_irq(&cm_id_priv->lock); cm_process_work(cm_id_priv, work); + /* + * Since this ID was just created and was not made visible to other MAD + * handlers until the cm_finalize_id() above we know that the + * cm_process_work() will deliver the event and the listen_cm_id + * embedded in the event can be derefed here. + */ cm_deref_id(listen_cm_id_priv); return 0; rejected: - refcount_dec(&cm_id_priv->refcount); cm_deref_id(listen_cm_id_priv); destroy: - ib_destroy_cm_id(cm_id); + ib_destroy_cm_id(&cm_id_priv->id); return ret; } |