* [PATCH v1] drivers/acpi/scan.c: Document why we don't need the device_hotplug_lock
@ 2019-07-31 13:53 David Hildenbrand
2019-07-31 14:17 ` Michal Hocko
2019-08-01 16:42 ` Rafael J. Wysocki
0 siblings, 2 replies; 3+ messages in thread
From: David Hildenbrand @ 2019-07-31 13:53 UTC (permalink / raw)
To: linux-kernel
Cc: linux-mm, linux-acpi, David Hildenbrand, Rafael J . Wysocki,
Michal Hocko, Oscar Salvador, Andrew Morton
Let's document why the lock is not needed in acpi_scan_init(), right now
this is not really obvious.
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
@Andrew, can you drop "drivers/acpi/scan.c: acquire device_hotplug_lock in
acpi_scan_init()" and add this patch instead? Thanks
---
drivers/acpi/scan.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 0e28270b0fd8..8444af6cd514 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -2204,6 +2204,12 @@ int __init acpi_scan_init(void)
acpi_gpe_apply_masked_gpes();
acpi_update_all_gpes();
+ /*
+ * Although we call__add_memory() that is documented to require the
+ * device_hotplug_lock, it is not necessary here because this is an
+ * early code when userspace or any other code path cannot trigger
+ * hotplug/hotunplug operations.
+ */
mutex_lock(&acpi_scan_lock);
/*
* Enumerate devices in the ACPI namespace.
--
2.21.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v1] drivers/acpi/scan.c: Document why we don't need the device_hotplug_lock
2019-07-31 13:53 [PATCH v1] drivers/acpi/scan.c: Document why we don't need the device_hotplug_lock David Hildenbrand
@ 2019-07-31 14:17 ` Michal Hocko
2019-08-01 16:42 ` Rafael J. Wysocki
1 sibling, 0 replies; 3+ messages in thread
From: Michal Hocko @ 2019-07-31 14:17 UTC (permalink / raw)
To: David Hildenbrand
Cc: linux-kernel, linux-mm, linux-acpi, Rafael J . Wysocki,
Oscar Salvador, Andrew Morton
On Wed 31-07-19 15:53:06, David Hildenbrand wrote:
> Let's document why the lock is not needed in acpi_scan_init(), right now
> this is not really obvious.
>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Thanks!
> ---
>
> @Andrew, can you drop "drivers/acpi/scan.c: acquire device_hotplug_lock in
> acpi_scan_init()" and add this patch instead? Thanks
>
> ---
> drivers/acpi/scan.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 0e28270b0fd8..8444af6cd514 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -2204,6 +2204,12 @@ int __init acpi_scan_init(void)
> acpi_gpe_apply_masked_gpes();
> acpi_update_all_gpes();
>
> + /*
> + * Although we call__add_memory() that is documented to require the
> + * device_hotplug_lock, it is not necessary here because this is an
> + * early code when userspace or any other code path cannot trigger
> + * hotplug/hotunplug operations.
> + */
> mutex_lock(&acpi_scan_lock);
> /*
> * Enumerate devices in the ACPI namespace.
> --
> 2.21.0
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v1] drivers/acpi/scan.c: Document why we don't need the device_hotplug_lock
2019-07-31 13:53 [PATCH v1] drivers/acpi/scan.c: Document why we don't need the device_hotplug_lock David Hildenbrand
2019-07-31 14:17 ` Michal Hocko
@ 2019-08-01 16:42 ` Rafael J. Wysocki
1 sibling, 0 replies; 3+ messages in thread
From: Rafael J. Wysocki @ 2019-08-01 16:42 UTC (permalink / raw)
To: David Hildenbrand, linux-kernel
Cc: linux-mm, linux-acpi, Michal Hocko, Oscar Salvador, Andrew Morton
On 7/31/2019 3:53 PM, David Hildenbrand wrote:
> Let's document why the lock is not needed in acpi_scan_init(), right now
> this is not really obvious.
>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>
> @Andrew, can you drop "drivers/acpi/scan.c: acquire device_hotplug_lock in
> acpi_scan_init()" and add this patch instead? Thanks
>
> ---
> drivers/acpi/scan.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 0e28270b0fd8..8444af6cd514 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -2204,6 +2204,12 @@ int __init acpi_scan_init(void)
> acpi_gpe_apply_masked_gpes();
> acpi_update_all_gpes();
>
> + /*
> + * Although we call__add_memory() that is documented to require the
> + * device_hotplug_lock, it is not necessary here because this is an
> + * early code when userspace or any other code path cannot trigger
> + * hotplug/hotunplug operations.
> + */
> mutex_lock(&acpi_scan_lock);
> /*
> * Enumerate devices in the ACPI namespace.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-07-31 13:53 [PATCH v1] drivers/acpi/scan.c: Document why we don't need the device_hotplug_lock David Hildenbrand
2019-07-31 14:17 ` Michal Hocko
2019-08-01 16:42 ` Rafael J. Wysocki
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