fx chen writes:
> hello!
> we found tgtd happen core dump and fix it。
[...]
Hi,
I believe we've hit the same problem recently (a free'd command hanging
on a session's cmd_list), and I have the same suspicion about conn_close.
I'm attaching my own version of a preliminary fix, that avoids examining
the entire cmd_list on each task deallocation.
I make use of the fact that a task's c_hlist during iscsi_free_task is
one of the following:
* an empty list head (task->c_hlist->next == task->c_hlist), if a task
was allocated by iscsi_alloc_task and c_hlist was INIT_LIST_HEAD'ed
and never touched
* a pair of null pointers for next and prev, if a task has been
list_del'ed from a cmd_list (or allocated by raw iscsi_tcp_alloc_task,
with all fields memset to 0 -- happens to "ping" NOOP-INs).
* a valid non-empty member of a cmd_list chain, in all other cases
(prev!=next captures this condition perfectly).
Therefore when we have c_hlist->prev!=c_hlist->next in iscsi_free_task,
we can list_del safely, removing the task from whatever cmd_list it was
on.
Do you see any problem with my version of a fix? (see attachment)
P.S.
I believe it would be better to learn _where exactly_ does conn_close
call iscsi_free_task instead of iscsi_free_cmd_task, and why it happens,
and fix it more "precisely" in that place.
However, having a crude, overprotective fix is better than not having
any. And as crude fixes go, I'd prefer the one which doesn't walk
cmd_list on a task deallocation.
diff --git a/usr/iscsi/iscsid.c b/usr/iscsi/iscsid.c
index b7ee0ad..dbb80a7 100644
--- a/usr/iscsi/iscsid.c
+++ b/usr/iscsi/iscsid.c
@@ -1225,6 +1225,12 @@ void iscsi_free_task(struct iscsi_task *task)
list_del(&task->c_siblings);
+ if (task->c_hlist.next != task->c_hlist.prev) {
+ eprintf("task on c_hlist: %p %p %p\n",
+ task, task->c_hlist.prev, task->c_hlist.next);
+ list_del(&task->c_hlist);
+ }
+
conn->tp->free_data_buf(conn, scsi_get_in_buffer(&task->scmd));
conn->tp->free_data_buf(conn, scsi_get_out_buffer(&task->scmd));
--
Regards, Anton Kovalenko | +7(916)345-34-02 | Elektrostal' MO, Russia
