Re: + acpi-scan-acquire-device_hotplug_lock-in-acpi_scan_init.patch added to -mm tree

Re: + acpi-scan-acquire-device_hotplug_lock-in-acpi_scan_init.patch added to -mm tree

[Rafael J. Wysocki]

On Thursday, July 25, 2019 2:06:20 AM CEST akpm@linux-foundation.org wrote:
> 
> The patch titled
>      Subject: drivers/acpi/scan.c: acquire device_hotplug_lock in acpi_scan_init()
> has been added to the -mm tree.  Its filename is
>      acpi-scan-acquire-device_hotplug_lock-in-acpi_scan_init.patch
> 
> This patch should soon appear at
>     http://ozlabs.org/~akpm/mmots/broken-out/acpi-scan-acquire-device_hotplug_lock-in-acpi_scan_init.patch
> and later at
>     http://ozlabs.org/~akpm/mmotm/broken-out/acpi-scan-acquire-device_hotplug_lock-in-acpi_scan_init.patch
> 
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>       reply-to-all to that, adding suitable additional cc's
> 
> *** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
> 
> The -mm tree is included into linux-next and is updated
> there every 3-4 working days
> 
> ------------------------------------------------------
> From: David Hildenbrand <david@redhat.com>
> Subject: drivers/acpi/scan.c: acquire device_hotplug_lock in acpi_scan_init()
> 
> We end up calling __add_memory() without the device hotplug lock held.  (I
> used a local patch to assert in __add_memory() that the
> device_hotplug_lock is held - I might upstream that as well soon)
> 
> [   26.771684]        create_memory_block_devices+0xa4/0x140
> [   26.772952]        add_memory_resource+0xde/0x200
> [   26.773987]        __add_memory+0x6e/0xa0
> [   26.775161]        acpi_memory_device_add+0x149/0x2b0
> [   26.776263]        acpi_bus_attach+0xf1/0x1f0
> [   26.777247]        acpi_bus_attach+0x66/0x1f0
> [   26.778268]        acpi_bus_attach+0x66/0x1f0
> [   26.779073]        acpi_bus_attach+0x66/0x1f0
> [   26.780143]        acpi_bus_scan+0x3e/0x90
> [   26.780844]        acpi_scan_init+0x109/0x257
> [   26.781638]        acpi_init+0x2ab/0x30d
> [   26.782248]        do_one_initcall+0x58/0x2cf
> [   26.783181]        kernel_init_freeable+0x1bd/0x247
> [   26.784345]        kernel_init+0x5/0xf1
> [   26.785314]        ret_from_fork+0x3a/0x50
> 
> So perform the locking just like in acpi_device_hotplug().
> 
> Link: http://lkml.kernel.org/r/20190724143017.12841-1-david@redhat.com
> Signed-off-by: David Hildenbrand <david@redhat.com>
> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> Cc: Len Brown <lenb@kernel.org
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Michal Hocko <mhocko@suse.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
> 
>  drivers/acpi/scan.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> --- a/drivers/acpi/scan.c~acpi-scan-acquire-device_hotplug_lock-in-acpi_scan_init
> +++ a/drivers/acpi/scan.c
> @@ -2204,7 +2204,9 @@ int __init acpi_scan_init(void)
>  	acpi_gpe_apply_masked_gpes();
>  	acpi_update_all_gpes();
>  
> +	lock_device_hotplug();
>  	mutex_lock(&acpi_scan_lock);
> +
>  	/*
>  	 * Enumerate devices in the ACPI namespace.
>  	 */
> @@ -2232,6 +2234,7 @@ int __init acpi_scan_init(void)
>  
>   out:
>  	mutex_unlock(&acpi_scan_lock);
> +	unlock_device_hotplug();
>  	return result;
>  }
>  
> _
> 
> Patches currently in -mm which might be from david@redhat.com are
> 
> acpi-scan-acquire-device_hotplug_lock-in-acpi_scan_init.patch
> drivers-base-nodec-simplify-unregister_memory_block_under_nodes.patch
> 
>