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Message-ID: <c3ef8123-1fcc-7289-c475-c753de44d564@redhat.com>
Date: Tue, 19 Sep 2023 10:31:17 +1000
From: Gavin Shan <gshan@...hat.com>
To: James Morse <james.morse@....com>, linux-pm@...r.kernel.org,
loongarch@...ts.linux.dev, linux-acpi@...r.kernel.org,
linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-riscv@...ts.infradead.org, kvmarm@...ts.linux.dev
Cc: x86@...nel.org, Salil Mehta <salil.mehta@...wei.com>,
Russell King <linux@...linux.org.uk>,
Jean-Philippe Brucker <jean-philippe@...aro.org>,
jianyong.wu@....com, justin.he@....com
Subject: Re: [RFC PATCH v2 21/35] ACPI: Add post_eject to struct
acpi_scan_handler for cpu hotplug
On 9/14/23 02:38, James Morse wrote:
> struct acpi_scan_handler has a detach callback that is used to remove
> a driver when a bus is changed. When interacting with an eject-request,
> the detach callback is called before _EJ0.
>
> This means the ACPI processor driver can't use _STA to determine if a
> CPU has been made not-present, or some of the other _STA bits have been
> changed. acpi_processor_remove() needs to know the value of _STA after
> _EJ0 has been called.
>
It's helpful to mention which ACPI processor driver needs to use _STA
to determine the status here. I guess the ACPI processor driver will
behave differently depending on the status.
> Add a post_eject callback to struct acpi_scan_handler. This is called
> after acpi_scan_hot_remove() has successfully called _EJ0. Because
> acpi_bus_trim_one() also clears the handler pointer, it needs to be
> told if the caller will go on to call acpi_bus_post_eject(), so
> that acpi_device_clear_enumerated() and clearing the handler pointer
> can be deferred. The existing not-used pointer is used for this.
>
> Signed-off-by: James Morse <james.morse@....com>
> ---
> drivers/acpi/acpi_processor.c | 4 +--
> drivers/acpi/scan.c | 52 ++++++++++++++++++++++++++++++-----
> include/acpi/acpi_bus.h | 1 +
> 3 files changed, 48 insertions(+), 9 deletions(-)
>
Reviewed-by: Gavin Shan <gshan@...hat.com>
> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> index 22a15a614f95..00dcc23d49a8 100644
> --- a/drivers/acpi/acpi_processor.c
> +++ b/drivers/acpi/acpi_processor.c
> @@ -459,7 +459,7 @@ static int acpi_processor_add(struct acpi_device *device,
>
> #ifdef CONFIG_ACPI_HOTPLUG_PRESENT_CPU
> /* Removal */
> -static void acpi_processor_remove(struct acpi_device *device)
> +static void acpi_processor_post_eject(struct acpi_device *device)
> {
> struct acpi_processor *pr;
>
> @@ -627,7 +627,7 @@ static struct acpi_scan_handler processor_handler = {
> .ids = processor_device_ids,
> .attach = acpi_processor_add,
> #ifdef CONFIG_ACPI_HOTPLUG_PRESENT_CPU
> - .detach = acpi_processor_remove,
> + .post_eject = acpi_processor_post_eject,
> #endif
> .hotplug = {
> .enabled = true,
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index a675333618ae..b6d2f01640a9 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -244,18 +244,28 @@ static int acpi_scan_try_to_offline(struct acpi_device *device)
> return 0;
> }
>
> -static int acpi_bus_trim_one(struct acpi_device *adev, void *not_used)
> +/**
> + * acpi_bus_trim_one() - Detach scan handlers and drivers from ACPI device
> + * objects.
> + * @adev: Root of the ACPI namespace scope to walk.
> + * @eject: Pointer to a bool that indicates if this was due to an
> + * eject-request.
> + *
> + * Must be called under acpi_scan_lock.
> + * If @eject points to true, clearing the device enumeration is deferred until
> + * acpi_bus_post_eject() is called.
> + */
> +static int acpi_bus_trim_one(struct acpi_device *adev, void *eject)
> {
> struct acpi_scan_handler *handler = adev->handler;
> + bool is_eject = *(bool *)eject;
>
> - acpi_dev_for_each_child_reverse(adev, acpi_bus_trim_one, NULL);
> + acpi_dev_for_each_child_reverse(adev, acpi_bus_trim_one, eject);
>
> adev->flags.match_driver = false;
> if (handler) {
> if (handler->detach)
> handler->detach(adev);
> -
> - adev->handler = NULL;
> } else {
> device_release_driver(&adev->dev);
> }
> @@ -265,7 +275,12 @@ static int acpi_bus_trim_one(struct acpi_device *adev, void *not_used)
> */
> acpi_device_set_power(adev, ACPI_STATE_D3_COLD);
> adev->flags.initialized = false;
> - acpi_device_clear_enumerated(adev);
> +
> + /* For eject this is deferred to acpi_bus_post_eject() */
> + if (!is_eject) {
> + adev->handler = NULL;
> + acpi_device_clear_enumerated(adev);
> + }
>
> return 0;
> }
> @@ -278,15 +293,36 @@ static int acpi_bus_trim_one(struct acpi_device *adev, void *not_used)
> */
> void acpi_bus_trim(struct acpi_device *adev)
> {
> - acpi_bus_trim_one(adev, NULL);
> + bool eject = false;
> +
> + acpi_bus_trim_one(adev, &eject);
> }
> EXPORT_SYMBOL_GPL(acpi_bus_trim);
>
> +static int acpi_bus_post_eject(struct acpi_device *adev, void *not_used)
> +{
> + struct acpi_scan_handler *handler = adev->handler;
> +
> + acpi_dev_for_each_child_reverse(adev, acpi_bus_post_eject, NULL);
> +
> + if (handler) {
> + if (handler->post_eject)
> + handler->post_eject(adev);
> +
> + adev->handler = NULL;
> + }
> +
> + acpi_device_clear_enumerated(adev);
> +
> + return 0;
> +}
> +
> static int acpi_scan_hot_remove(struct acpi_device *device)
> {
> acpi_handle handle = device->handle;
> unsigned long long sta;
> acpi_status status;
> + bool eject = true;
>
> if (device->handler && device->handler->hotplug.demand_offline) {
> if (!acpi_scan_is_offline(device, true))
> @@ -299,7 +335,7 @@ static int acpi_scan_hot_remove(struct acpi_device *device)
>
> acpi_handle_debug(handle, "Ejecting\n");
>
> - acpi_bus_trim(device);
> + acpi_bus_trim_one(device, &eject);
>
> acpi_evaluate_lck(handle, 0);
> /*
> @@ -322,6 +358,8 @@ static int acpi_scan_hot_remove(struct acpi_device *device)
> } else if (sta & ACPI_STA_DEVICE_ENABLED) {
> acpi_handle_warn(handle,
> "Eject incomplete - status 0x%llx\n", sta);
> + } else {
> + acpi_bus_post_eject(device, NULL);
> }
>
> return 0;
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index 254685085c82..1b7e1acf925b 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -127,6 +127,7 @@ struct acpi_scan_handler {
> bool (*match)(const char *idstr, const struct acpi_device_id **matchid);
> int (*attach)(struct acpi_device *dev, const struct acpi_device_id *id);
> void (*detach)(struct acpi_device *dev);
> + void (*post_eject)(struct acpi_device *dev);
> void (*bind)(struct device *phys_dev);
> void (*unbind)(struct device *phys_dev);
> struct acpi_hotplug_profile hotplug;
Thanks,
Gavin
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