linux-kernel - Re: [PATCH v5 4/5] soc: qcom: rpmh-rsc: Simplify locking by eliminating the per-TCS lock

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Message-ID: <158775156694.135303.3535369004080151247@swboyd.mtv.corp.google.com>
Date:   Fri, 24 Apr 2020 11:06:06 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rafael.j.wysocki@...el.com
Cc:     evgreen@...omium.org, mka@...omium.org, mkshah@...eaurora.org,
        Douglas Anderson <dianders@...omium.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 4/5] soc: qcom: rpmh-rsc: Simplify locking by eliminating the per-TCS lock

Quoting Douglas Anderson (2020-04-24 09:46:56)
> @@ -581,24 +575,19 @@ static int tcs_write(struct rsc_drv *drv, const struct tcs_request *msg)
>         if (IS_ERR(tcs))
>                 return PTR_ERR(tcs);
>  
> -       spin_lock_irqsave(&tcs->lock, flags);
> -       spin_lock(&drv->lock);
> +       spin_lock_irqsave(&drv->lock, flags);
>         /*
>          * The h/w does not like if we send a request to the same address,
>          * when one is already in-flight or being processed.
>          */
>         ret = check_for_req_inflight(drv, tcs, msg);
> -       if (ret) {
> -               spin_unlock(&drv->lock);
> -               goto done_write;
> -       }
> +       if (ret)
> +               goto unlock;
>  
> -       tcs_id = find_free_tcs(tcs);
> -       if (tcs_id < 0) {
> -               ret = tcs_id;
> -               spin_unlock(&drv->lock);
> -               goto done_write;
> -       }
> +       ret = find_free_tcs(tcs);
> +       if (ret < 0)
> +               goto unlock;
> +       tcs_id = ret;

Sorry, missed this. We should keep the tcs_id = find_free_tcs() thing
and then assign ret to it on failure. Otherwise the return value of this
function is -EBUSY or the tcs_id number instead of -EBUSY or 0.

>  
>         tcs->req[tcs_id - tcs->offset] = msg;
>         set_bit(tcs_id, drv->tcs_in_use);