Messages in this thread Patch in this message | | | Date | Mon, 01 May 2006 16:02:13 +0300 | From | Or Gerlitz <> | Subject | Re: [openib-general] [PATCH 5/6] iser RDMA CM (CMA) and IB verbsinteraction |
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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.
>> + src = (struct sockaddr *)src_addr; >> + dst = (struct sockaddr *)dst_addr; >> + err = rdma_resolve_addr(ib_conn->cma_id, src, dst, 1000); >> + if (err) { >> + iser_err("rdma_resolve_addr failed: %d\n", err); >> + goto addr_failure; >> + } >> + >> + if (!non_blocking) { >> + wait_event_interruptible(ib_conn->wait, >> + atomic_read(&ib_conn->state) != ISER_CONN_PENDING); >> + >> + if (atomic_read(&ib_conn->state) != ISER_CONN_UP) { >> + err = -EIO; >> + goto connect_failure; >> + } >> + } >> + >> + mutex_lock(&ig.connlist_mutex); >> + list_add(&ib_conn->conn_list, &ig.connlist); >> + mutex_unlock(&ig.connlist_mutex);
> Not sure if there's a race here or not, but rdma_resolve_addr() will result in a > callback from a separate thread. That callback could occur before the ib_conn > is added to the ig.connlist. Do you assume that ib_conn is in the connlist in > any of the callbacks?
No, i don't assume this in the callbacks. ib_conn is inserted to the list in iser_connect and being lookup-ed in ep_poll, conn_bind and ep_disconnect where each subset of the latter three functions are serialized are iser_connect since they are called by the same user space process (iscsid, via iscsi netlink u/k IPC mechanism).
However, in a review i have made to fully answer your question i have found a possible double call to iser_conn_release where the fix below handles it.
------------------------------------------------------------------------ r6802 | ogerlitz | 2006-05-01 12:27:12 +0300 (Mon, 01 May 2006) | 5 lines
move the ib conn deletion from the global connlist to iser_conn_release, fix ep_disconnect to call conn_terminate or conn_release but not both.
Signed-off-by: Or Gerlitz <ogerlitz@voltaire.com>
Index: iser_verbs.c =================================================================== --- iser_verbs.c (revision 6761) +++ iser_verbs.c (revision 6802) @@ -301,10 +301,6 @@ void iser_conn_terminate(struct iser_con wait_event_interruptible(ib_conn->wait, (atomic_read(&ib_conn->state) == ISER_CONN_DOWN));
- mutex_lock(&ig.connlist_mutex); - list_del(&ib_conn->conn_list); - mutex_unlock(&ig.connlist_mutex); - iser_conn_release(ib_conn); }
@@ -463,6 +459,7 @@ int iser_conn_init(struct iser_conn **ib atomic_set(&ib_conn->post_send_buf_count, 0); INIT_WORK(&ib_conn->comperror_work, iser_comp_error_worker, ib_conn); + INIT_LIST_HEAD(&ib_conn->conn_list);
*ibconn = ib_conn; return 0; @@ -541,6 +538,10 @@ void iser_conn_release(struct iser_conn
BUG_ON(atomic_read(&ib_conn->state) != ISER_CONN_DOWN);
+ mutex_lock(&ig.connlist_mutex); + list_del(&ib_conn->conn_list); + mutex_unlock(&ig.connlist_mutex); + iser_free_ib_conn_res(ib_conn); ib_conn->device = NULL; /* on EVENT_ADDR_ERROR there's no device yet for this conn */ Index: iscsi_iser.c =================================================================== --- iscsi_iser.c (revision 6761) +++ iscsi_iser.c (revision 6802) @@ -680,8 +680,8 @@ iscsi_iser_ep_disconnect(__u64 ep_handle
if (atomic_read(&ib_conn->state) == ISER_CONN_UP) iser_conn_terminate(ib_conn); - - iser_conn_release(ib_conn); + else + iser_conn_release(ib_conn); }
static struct scsi_host_template iscsi_iser_sht = {
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