Re: [PATCH] net/p9/trans_fd.c: fix double list_del()

On 07/24/2018 12:19 PM, Dominique Martinet wrote:

Tomas Bortoli wrote on Tue, Jul 24, 2018:

quoted

quoted

quoted

@@ -228,6 +226,7 @@ static void p9_conn_cancel(struct p9_conn *m, int err)
 			req->t_err = err;
 		p9_client_cb(m->client, req, REQ_STATUS_ERROR);
 	}
+	spin_unlock(&m->client->lock);

If you want to expand the ranges of client->lock, the cancel_list will not
be necessary, you can optimize this code.

Unfortunately, not. Moving the spin_lock() before the for makes the
crash appear again. This because the calls to list_move() in the for
before delete all the elements from req->req_list, so the list is empty,
another call to list_del() would trigger a double del.
That's why we hold the lock to update the status of all those requests..
otherwise we have again the race with p9_fd_cancel().

What (I think) he meant is that since you're holding the lock all the
way, you don't need to transfer all the items to a temporary list to
loop on it immediately afterwards, but you could call the client cb
directly.

Yeah that is possible.

I'm personally not a fan of this approach as that would duplicate the
code, even if the loop isn't big...

Yep

This code is only called at disconnect time so I think using the extra
list doesn't hurt anyone; but as usual do what you feel is better; I
don't mind much either way.

I think it's fine as it is.