linux-kernel - Re: [PATCH] base: power: domain: Replace mdelay with msleep

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 9 Feb 2018 14:58:21 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] base: power: domain: Replace mdelay with msleep

On 26 January 2018 at 09:38, Jia-Ju Bai <baijiaju1990@...il.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@...il.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