linux-kernel - Re: 174cc7187e6f ACPICA: Tables: Back port acpi_get_table_with_size() and early_acpi_os_unmap

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Date:   Wed, 11 Jan 2017 04:42:16 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        "Zheng, Lv" <lv.zheng@...el.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "Moore, Robert" <robert.moore@...el.com>,
        "J?rg R?del" <joro@...tes.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>
Subject: Re: 174cc7187e6f ACPICA: Tables: Back port acpi_get_table_with_size()
 and early_acpi_os_unmap_memory() from Linux kernel

On Tue, Jan 10, 2017 at 10:41 AM, Borislav Petkov <bp@...en8.de> wrote:
> On Tue, Jan 10, 2017 at 02:27:16AM +0100, Rafael J. Wysocki wrote:
>> Well, if the https://patchwork.kernel.org/patch/9504277/ patch from Lv
>> worked, the attached one should work too (please test), but it can be
>> justified in a slightly more convincing way.
>
> No workie:
>
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index 57fb5f4..acb6118 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -378,7 +378,11 @@ static void acpi_os_drop_map_ref(struct acpi_ioremap *map)
>  static void acpi_os_map_cleanup(struct acpi_ioremap *map)
>  {
>         if (!map->refcount) {
> -               synchronize_rcu_expedited();
> +               if (acpi_os_initialized) {
> +                       pr_err("%s: acpi_os_initialized\n", __func__);
> +                       synchronize_rcu_expedited();
> +               }
> +
>                 acpi_unmap(map->phys, map->virt);
>                 kfree(map);
>         }
>
> The pr_err() gets issued before the box hangs.
>
> Lv's version which set the bool in acpi_os_map_generic_address() did
> work though.

Well, it would if nothing mapped by acpi_os_map_generic_address() was
in the memory address space, for example, but then it would never use
the RCU synchronization as well (not good).

Basically, we need to find a point during the initialization such that
acpi_os_read/write_memory() is not invoked earlier and set a flag in
there.

Let's try the attached one.

BTW, I'm going to travel to the LCA starting tomorrow, so I guess I
will be a bit unresponsive during the next few days.

Thanks,
Rafael

View attachment "acpi-debug-table-load.patch" of type "text/x-patch" (2296 bytes)