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
---
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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