Re: [RFC PATCH v2 21/35] ACPI: Add post_eject to struct acpi_scan_handler for cpu hotplug

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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@xxxxxxx>
---
  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@xxxxxxxxxx>

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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