On 11/09/2016 03:21 AM, Chris Leech wrote:
> On Mon, Nov 07, 2016 at 04:23:10PM -0200, Guilherme G. Piccoli wrote:
>>
>> Sure! Count on us to test any patches. I guess the first step is to
>> reproduce on upstream right? We haven't tested specifically this
>> scenario for long time. Will try to reproduce on 4.9-rc4 and update here.
>
> Great, I'm looking forward to hearing the result.
>
> Assuming it reproduces, I don't think this level of fine grained locking
> is necessarily the best solution, but it may help confirm the problem.
> Especially if the WARN_ONCE I slipped in here triggers.
>
> - Chris
Chris, I'm not able to reproduce right now - environment was
misconfigured, and now I'm leaving the office for 20 days.
Will test as soon as I'm back!
Thanks,
Guilherme
>
> ---
>
> diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
> index f9b6fba..fbd18ab 100644
> --- a/drivers/scsi/libiscsi.c
> +++ b/drivers/scsi/libiscsi.c
> @@ -560,8 +560,12 @@ static void iscsi_complete_task(struct iscsi_task *task, int state)
> WARN_ON_ONCE(task->state == ISCSI_TASK_FREE);
> task->state = state;
>
> - if (!list_empty(&task->running))
> + spin_lock_bh(&conn->taskqueuelock);
> + if (!list_empty(&task->running)) {
> + WARN_ONCE(1, "iscsi_complete_task while task on list");
> list_del_init(&task->running);
> + }
> + spin_unlock_bh(&conn->taskqueuelock);
>
> if (conn->task == task)
> conn->task = NULL;
> @@ -783,7 +787,9 @@ __iscsi_conn_send_pdu(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
> if (session->tt->xmit_task(task))
> goto free_task;
> } else {
> + spin_lock_bh(&conn->taskqueuelock);
> list_add_tail(&task->running, &conn->mgmtqueue);
> + spin_unlock_bh(&conn->taskqueuelock);
> iscsi_conn_queue_work(conn);
> }
>
> @@ -1474,8 +1480,10 @@ void iscsi_requeue_task(struct iscsi_task *task)
> * this may be on the requeue list already if the xmit_task callout
> * is handling the r2ts while we are adding new ones
> */
> + spin_lock_bh(&conn->taskqueuelock);
> if (list_empty(&task->running))
> list_add_tail(&task->running, &conn->requeue);
> + spin_unlock_bh(&conn->taskqueuelock);
> iscsi_conn_queue_work(conn);
> }
> EXPORT_SYMBOL_GPL(iscsi_requeue_task);
> @@ -1512,22 +1520,26 @@ static int iscsi_data_xmit(struct iscsi_conn *conn)
> * only have one nop-out as a ping from us and targets should not
> * overflow us with nop-ins
> */
> + spin_lock_bh(&conn->taskqueuelock);
> check_mgmt:
> while (!list_empty(&conn->mgmtqueue)) {
> conn->task = list_entry(conn->mgmtqueue.next,
> struct iscsi_task, running);
> list_del_init(&conn->task->running);
> + spin_unlock_bh(&conn->taskqueuelock);
> if (iscsi_prep_mgmt_task(conn, conn->task)) {
> /* regular RX path uses back_lock */
> spin_lock_bh(&conn->session->back_lock);
> __iscsi_put_task(conn->task);
> spin_unlock_bh(&conn->session->back_lock);
> conn->task = NULL;
> + spin_lock_bh(&conn->taskqueuelock);
> continue;
> }
> rc = iscsi_xmit_task(conn);
> if (rc)
> goto done;
> + spin_lock_bh(&conn->taskqueuelock);
> }
>
> /* process pending command queue */
> @@ -1535,19 +1547,24 @@ static int iscsi_data_xmit(struct iscsi_conn *conn)
> conn->task = list_entry(conn->cmdqueue.next, struct iscsi_task,
> running);
> list_del_init(&conn->task->running);
> + spin_unlock_bh(&conn->taskqueuelock);
> if (conn->session->state == ISCSI_STATE_LOGGING_OUT) {
> fail_scsi_task(conn->task, DID_IMM_RETRY);
> + spin_lock_bh(&conn->taskqueuelock);
> continue;
> }
> rc = iscsi_prep_scsi_cmd_pdu(conn->task);
> if (rc) {
> if (rc == -ENOMEM || rc == -EACCES) {
> + spin_lock_bh(&conn->taskqueuelock);
> list_add_tail(&conn->task->running,
> &conn->cmdqueue);
> conn->task = NULL;
> + spin_unlock_bh(&conn->taskqueuelock);
> goto done;
> } else
> fail_scsi_task(conn->task, DID_ABORT);
> + spin_lock_bh(&conn->taskqueuelock);
> continue;
> }
> rc = iscsi_xmit_task(conn);
> @@ -1558,6 +1575,7 @@ static int iscsi_data_xmit(struct iscsi_conn *conn)
> * we need to check the mgmt queue for nops that need to
> * be sent to aviod starvation
> */
> + spin_lock_bh(&conn->taskqueuelock);
> if (!list_empty(&conn->mgmtqueue))
> goto check_mgmt;
> }
> @@ -1577,12 +1595,15 @@ static int iscsi_data_xmit(struct iscsi_conn *conn)
> conn->task = task;
> list_del_init(&conn->task->running);
> conn->task->state = ISCSI_TASK_RUNNING;
> + spin_unlock_bh(&conn->taskqueuelock);
> rc = iscsi_xmit_task(conn);
> if (rc)
> goto done;
> + spin_lock_bh(&conn->taskqueuelock);
> if (!list_empty(&conn->mgmtqueue))
> goto check_mgmt;
> }
> + spin_unlock_bh(&conn->taskqueuelock);
> spin_unlock_bh(&conn->session->frwd_lock);
> return -ENODATA;
>
> @@ -1738,7 +1759,9 @@ int iscsi_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *sc)
> goto prepd_reject;
> }
> } else {
> + spin_lock_bh(&conn->taskqueuelock);
> list_add_tail(&task->running, &conn->cmdqueue);
> + spin_unlock_bh(&conn->taskqueuelock);
> iscsi_conn_queue_work(conn);
> }
>
> @@ -2897,6 +2920,7 @@ iscsi_conn_setup(struct iscsi_cls_session *cls_session, int dd_size,
> INIT_LIST_HEAD(&conn->mgmtqueue);
> INIT_LIST_HEAD(&conn->cmdqueue);
> INIT_LIST_HEAD(&conn->requeue);
> + spin_lock_init(&conn->taskqueuelock);
> INIT_WORK(&conn->xmitwork, iscsi_xmitworker);
>
> /* allocate login_task used for the login/text sequences */
> diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h
> index 4d1c46a..c7b1dc7 100644
> --- a/include/scsi/libiscsi.h
> +++ b/include/scsi/libiscsi.h
> @@ -196,6 +196,7 @@ struct iscsi_conn {
> struct iscsi_task *task; /* xmit task in progress */
>
> /* xmit */
> + spinlock_t taskqueuelock; /* protects the next three lists */
> struct list_head mgmtqueue; /* mgmt (control) xmit queue */
> struct list_head cmdqueue; /* data-path cmd queue */
> struct list_head requeue; /* tasks needing another run */
>
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