linux-kernel - Re: [PATCH] soc: qcom: rpmh-rsc: Sleep waiting for tcs slots to be free

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Date:   Fri, 24 Jul 2020 12:49:56 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Maulik Shah <mkshah@...eaurora.org>,
        Lina Iyer <ilina@...eaurora.org>
Subject: Re: [PATCH] soc: qcom: rpmh-rsc: Sleep waiting for tcs slots to be free

Hi,

On Fri, Jul 24, 2020 at 12:44 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> > > -       if (ret)
> > > -               goto unlock;
> > >
> > > -       ret = find_free_tcs(tcs);
> > > -       if (ret < 0)
> > > -               goto unlock;
> > > -       tcs_id = ret;
> > > +       wait_event_lock_irq(drv->tcs_wait,
> > > +                           (tcs_id = claim_tcs_for_req(drv, tcs, msg)) >= 0,
> >
> > Even though claim_tcs_for_req() only returns 0 or -EBUSY today (IOW it
> > never returns error codes other than -EBUSY), should we handle it?  If
> > we don't, claim_tcs_for_req() should be very clear that it shouldn't
> > return any errors other than -EBUSY.
>
> Do you mean you want to change it to be
>
>         (tcs_id = claim_tcs_for_req(drv, tcs, msg)) != -EBUSY
>
> instead of >= 0? It should return the tcs_id that was claimed, not just
> 0 or -EBUSY.

Ah, right.  Yes, you got it right.  Of course then we have to add a
"if (tcd_id < 0) goto unlock", too.  If you think it's not worth
adding this then we just need to make sure it's super obvious in
claim_tcs_for_req() that it's not allowed to return other errors.

-Doug