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Date:   Mon, 24 Aug 2020 11:50:57 +0300
From:   Heikki Krogerus <heikki.krogerus@linux.intel.com>
To:     "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc:     Linux ACPI <linux-acpi@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        "Kenneth R. Crudup" <kenny@panix.com>
Subject: Re: [PATCH] ACPI: OSL: Prevent acpi_release_memory() from returning
 too early
Message-ID: <20200824085057.GA189773@kuha.fi.intel.com>
References: <6142241.0H6QnnlUA7@kreacher>
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On Fri, Aug 21, 2020 at 07:42:55PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> After commit 1757659d022b ("ACPI: OSL: Implement deferred unmapping
> of ACPI memory") in some cases acpi_release_memory() may return
> before the target memory mappings actually go away, because they
> are released asynchronously now.
> 
> Prevent it from returning prematurely by making it wait for the next
> RCU grace period to elapse, for all of the RCU callbacks to complete
> and for all of the scheduled work items to be flushed before
> returning.
> 
> Fixes: 1757659d022b ("ACPI: OSL: Implement deferred unmapping of ACPI memory")
> Reported-by: Kenneth R. Crudup <kenny@panix.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

FWIW:

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
>  drivers/acpi/osl.c |   19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
> 
> Index: linux-pm/drivers/acpi/osl.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/osl.c
> +++ linux-pm/drivers/acpi/osl.c
> @@ -1575,11 +1575,26 @@ static acpi_status acpi_deactivate_mem_r
>  acpi_status acpi_release_memory(acpi_handle handle, struct resource *res,
>  				u32 level)
>  {
> +	acpi_status status;
> +
>  	if (!(res->flags & IORESOURCE_MEM))
>  		return AE_TYPE;
>  
> -	return acpi_walk_namespace(ACPI_TYPE_REGION, handle, level,
> -				   acpi_deactivate_mem_region, NULL, res, NULL);
> +	status = acpi_walk_namespace(ACPI_TYPE_REGION, handle, level,
> +				     acpi_deactivate_mem_region, NULL,
> +				     res, NULL);
> +	if (ACPI_FAILURE(status))
> +		return status;
> +
> +	/*
> +	 * Wait for all of the mappings queued up for removal by
> +	 * acpi_deactivate_mem_region() to actually go away.
> +	 */
> +	synchronize_rcu();
> +	rcu_barrier();
> +	flush_scheduled_work();
> +
> +	return AE_OK;
>  }
>  EXPORT_SYMBOL_GPL(acpi_release_memory);

thanks,

-- 
heikki