linux-kernel - Re: [PATCH v2 2/3] driver core: Read atomic counter once in driver_probe

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Date:   Tue, 24 Mar 2020 13:55:00 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Ferry Toth <fntoth@...il.com>
Subject: Re: [PATCH v2 2/3] driver core: Read atomic counter once in driver_probe_done()

On Tue, Mar 24, 2020 at 1:20 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> Between printing the debug message and actual check atomic counter can be
> altered. For better debugging experience read atomic counter value only once.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Tested-by: Ferry Toth <fntoth@...il.com>

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

> ---
> v2: picked up tags
>  drivers/base/dd.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 43720beb5300..efd0e4c16ba5 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -669,9 +669,10 @@ static int really_probe_debug(struct device *dev, struct device_driver *drv)
>   */
>  int driver_probe_done(void)
>  {
> -       pr_debug("%s: probe_count = %d\n", __func__,
> -                atomic_read(&probe_count));
> -       if (atomic_read(&probe_count))
> +       int local_probe_count = atomic_read(&probe_count);
> +
> +       pr_debug("%s: probe_count = %d\n", __func__, local_probe_count);
> +       if (local_probe_count)
>                 return -EBUSY;
>         return 0;
>  }
> --
> 2.25.1
>