linux-kernel - Re: [PATCH] IB/ipoib: No need to hold the lock while printing the warning

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Date:   Mon, 11 Dec 2023 15:09:13 +0100
From:   Daniel Vacek <neelx@...hat.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Leon Romanovsky <leon@...nel.org>, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] IB/ipoib: No need to hold the lock while printing the warning

On Mon, Dec 11, 2023 at 2:25 PM Jason Gunthorpe <jgg@...pe.ca> wrote:
>
> On Mon, Dec 11, 2023 at 03:22:17PM +0200, Leon Romanovsky wrote:
>
> > Please fill some text in commit message.
>
> Yes, explain *why* you are doing this

Oh, sorry. I did not mention it but there's no particular reason
really. The @Subject says it all. There should be no logical or
functional change other than reducing the span of that critical
section. In other words, just nitpicking, not a big deal.

While checking the code (and past changes) related to the other issue
I also sent today I just noticed the way 08bc327629cbd added the
spin_lock before returning from this function and it appeared to me
it's clearer the way I'm proposing here.

Honestly, I was not looking into why the lock is released for that
completion. And I'm not changing that logic.

If this complete() can be called with priv->lock held, the cleanup
would look different, of course.

That said, If you'd like to keep this patch I can send a v2 with the
above details in the message body. Otherwise feel free to drop this.

--nX

> > > diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> > > index 5b3154503bf4..ae2c05806dcc 100644
> > > --- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> > > +++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
> > > @@ -536,17 +536,17 @@ static int ipoib_mcast_join(struct net_device *dev, struct ipoib_mcast *mcast)
> > >     multicast = ib_sa_join_multicast(&ipoib_sa_client, priv->ca, priv->port,
> > >                                      &rec, comp_mask, GFP_KERNEL,
> > >                                      ipoib_mcast_join_complete, mcast);
> > > -   spin_lock_irq(&priv->lock);
> > >     if (IS_ERR(multicast)) {
> > >             ret = PTR_ERR(multicast);
> > >             ipoib_warn(priv, "ib_sa_join_multicast failed, status %d\n", ret);
> > > +           spin_lock_irq(&priv->lock);
> > >             /* Requeue this join task with a backoff delay */
> > >             __ipoib_mcast_schedule_join_thread(priv, mcast, 1);
> > >             clear_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags);
> > >             spin_unlock_irq(&priv->lock);
> > >             complete(&mcast->done);
> > > -           spin_lock_irq(&priv->lock);
>
> It is super weird to unlock just around complete.
>
> Jason
>