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From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Fri, 9 Feb 2018 14:58:21 +0100
Message-ID: <CAPDyKFoft7aCoKtODz66AAjpDQELVhqGurFYBV6FHP9hzhy-Ug@mail.gmail.com>
Subject: Re: [PATCH] base: power: domain: Replace mdelay with msleep
To:     Jia-Ju Bai <baijiaju1990@gmail.com>
Cc:     "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Kevin Hilman <khilman@kernel.org>,
        Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On 26 January 2018 at 09:38, Jia-Ju Bai <baijiaju1990@gmail.com> wrote:
> After checking all possible call chains to genpd_dev_pm_detach() and
> genpd_dev_pm_attach() here,
> my tool finds that these functions are never called in atomic context,
> namely never in an interrupt handler or holding a spinlock.
> Thus mdelay can be replaced with msleep to avoid busy wait.
>
> This is found by a static analysis tool named DCNS written by myself.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
> ---
>  drivers/base/power/domain.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 0c80bea..f84ac72 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -2144,7 +2144,7 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off)
>                 if (ret != -EAGAIN)
>                         break;
>
> -               mdelay(i);
> +               msleep(i);

This looks like a nice improvement, however moving to msleep() makes
the call to cond_resched() below a bit superfluous. Perhaps remove
that as well.

>                 cond_resched();
>         }
>
> @@ -2231,7 +2231,7 @@ int genpd_dev_pm_attach(struct device *dev)
>                 if (ret != -EAGAIN)
>                         break;
>
> -               mdelay(i);
> +               msleep(i);

Ditto.

>                 cond_resched();
>         }
>         mutex_unlock(&gpd_list_lock);
> --
> 1.7.9.5
>

Kind regards
Uffe