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From:   Dmitry Safonov <0x7f454c46@gmail.com>
Date:   Thu, 21 Nov 2019 21:19:43 +0000
Message-ID: <CAJwJo6ZTSw93zKdN3i-YqVtEEwh4qWc22Hk-emHvJth+HsaQbQ@mail.gmail.com>
Subject: Re: [PATCH] ACPI: only free map once in osl.c
To:     Francesco Ruggeri <fruggeri@arista.com>
Cc:     lenb@kernel.org, "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        open list <linux-kernel@vger.kernel.org>,
        linux-acpi@vger.kernel.org
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Hi Francesco,

I believe, there's still an issue with your patch.

On Wed, 20 Nov 2019 at 05:50, Francesco Ruggeri <fruggeri@arista.com> wrote:
> @@ -472,10 +477,11 @@ void acpi_os_unmap_generic_address(struct acpi_generic_address *gas)
>                 mutex_unlock(&acpi_ioremap_lock);
>                 return;
>         }
> -       acpi_os_drop_map_ref(map);
> +       refcount = acpi_os_drop_map_ref(map);
>         mutex_unlock(&acpi_ioremap_lock);

Here comes acpi_os_get_iomem() increasing the refcount again.

>
> -       acpi_os_map_cleanup(map);
> +       if (!refcount)
> +               acpi_os_map_cleanup(map);
>  }
>  EXPORT_SYMBOL(acpi_os_unmap_generic_address);

And you free the acpi_ioremap that's being used:

>  static void acpi_os_map_cleanup(struct acpi_ioremap *map)
>  {
> -       if (!map->refcount) {
> -               synchronize_rcu_expedited();
> -               acpi_unmap(map->phys, map->virt);
> -               kfree(map);
> -       }
> +       synchronize_rcu_expedited();
> +       acpi_unmap(map->phys, map->virt);
> +       kfree(map);
>  }

Thanks,
             Dmitry