linux-kernel - Re: [PATCH rdma-next v3 8/8] IB/cm: Protect cm_dev, cm_ports and mad

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Date:   Wed, 26 May 2021 13:16:06 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Mark Zhang <markzhang@...dia.com>
Cc:     Leon Romanovsky <leon@...nel.org>,
        Doug Ledford <dledford@...hat.com>,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        Sean Hefty <sean.hefty@...el.com>
Subject: Re: [PATCH rdma-next v3 8/8] IB/cm: Protect cm_dev, cm_ports and
 mad_agent with kref and lock

On Wed, May 26, 2021 at 10:46:47AM +0800, Mark Zhang wrote:
> On 5/26/2021 4:00 AM, Jason Gunthorpe wrote:
> > On Tue, May 11, 2021 at 11:22:12AM +0300, Leon Romanovsky wrote:
> > > @@ -2139,6 +2197,8 @@ static int cm_req_handler(struct cm_work *work)
> > >   		sa_path_set_dmac(&work->path[0],
> > >   				 cm_id_priv->av.ah_attr.roce.dmac);
> > >   	work->path[0].hop_limit = grh->hop_limit;
> > > +
> > > +	cm_destroy_av(&cm_id_priv->av);
> > >   	ret = cm_init_av_by_path(&work->path[0], gid_attr, &cm_id_priv->av);
> > >   	if (ret) {
> > >   		int err;
> > 
> > Why add cm_destroy_av() here? The cm_id_priv was freshly created at
> > the top of this function and hasn't left the stack frame yet?
> > 
> Because it was initialized by cm_init_av_for_response() previously, so
> destroy it here as cm_init_av_by_path() will re-initialize it.

Oh.. ouch, I once tried to re-order this so it wasn't doing such crazy
stuff, but it was too hard.

Please just add a comment the destroy is for the
cm_init_av_for_response

Jason