Date:	Fri, 22 Feb 2013 17:51:28 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>, Toshi Kani <toshi.kani@...com>
CC:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>, Jiang Liu <liuj97@...il.com>
Subject: Re: [Update 3][PATCH 2/7] ACPI / scan: Introduce common code for
 ACPI-based device hotplug

2013/02/22 10:50, Rafael J. Wysocki wrote:
> On Thursday, February 21, 2013 06:12:21 PM Toshi Kani wrote:
>> On Fri, 2013-02-22 at 00:06 +0100, Rafael J. Wysocki wrote:
>>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>>
>>> Multiple drivers handling hotplug-capable ACPI device nodes install
>>> notify handlers covering the same types of events in a very similar
>>> way.  Moreover, those handlers are installed in separate namespace
>>> walks, although that really should be done during namespace scans
>>> carried out by acpi_bus_scan().  This leads to substantial code
>>> duplication, unnecessary overhead and behavior that is hard to
>>> follow.
>>>
>>> For this reason, introduce common code in drivers/acpi/scan.c for
>>> handling hotplug-related notification and carrying out device
>>> insertion and eject operations in a generic fashion, such that it
>>> may be used by all of the relevant drivers in the future.  To cover
>>> the existing differences between those drivers introduce struct
>>> acpi_hotplug_profile for representing collections of hotplug
>>> settings associated with different ACPI scan handlers that can be
>>> used by the drivers to make the common code reflect their current
>>> behavior.
>>>
>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>> ---
>>>
>>> This update fixes an issue pointed out by Toshi Kani (that
>>> ACPI_OST_EC_OSPM_* event source codes should not be used with _OST for events
>>> that we received a notification for from the platform firmware).
>>>
>>> Thanks,
>>> Rafael
>>>
>>> ---
>>>   drivers/acpi/scan.c     |  270 ++++++++++++++++++++++++++++++++++++++----------
>>>   include/acpi/acpi_bus.h |    7 +
>>>   2 files changed, 224 insertions(+), 53 deletions(-)
>>   :
>>> +static void acpi_bus_device_eject(void *context)
>>> +{
>>> +	acpi_handle handle = context;
>>> +	struct acpi_device *device = NULL;
>>> +	struct acpi_scan_handler *handler;
>>> +	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE;
>>> +
>>> +	mutex_lock(&acpi_scan_lock);
>>> +
>>> +	acpi_bus_get_device(handle, &device);
>>> +	if (!device)
>>> +		goto err_out;
>>> +
>>> +	handler = device->handler;
>>> +	if (!handler || !handler->hotplug.enabled) {
>>> +		ost_code = ACPI_OST_SC_EJECT_NOT_SUPPORTED;
>>> +		goto err_out;
>>> +	}
>>> +	acpi_evaluate_hotplug_ost(handle, ACPI_NOTIFY_EJECT_REQUEST,
>>> +				  ACPI_OST_SC_EJECT_IN_PROGRESS, NULL);
>>> +	if (handler->hotplug.autoeject) {
>>> +		int error;
>>> +
>>> +		get_device(&device->dev);
>>> +		error = acpi_scan_hot_remove(device);
>>> +		if (error)
>>> +			goto err_out;
>>> +	} else {
>>> +		device->flags.eject_pending = true;
>>>   	}
>>> +	if (handler->hotplug.uevents)
>>> +		kobject_uevent(&device->dev.kobj, KOBJ_OFFLINE);
>>
>> I confirmed that the _OST issue with hot-add is fixed.  Here is a new
>> one.  When autoeject is enabled, it crashes in kobject_uevent() since
>> the device is no longer valid.
>
> Well, this one is more difficult.
>
> I can change the ordering so that kobject_uevent() is called before
> acpi_scan_hot_remove(), but then user space may not know that the device is
> being removed at the moment (which still may fail).  Still, maybe this is
> OK, because user space will get KOBJ_REMOVE when the device actually goes
> away anyway.
>
> Or perhaps we can emit KOBJ_OFFLINE before acpi_scan_hot_remove() and if
> it fails, emit KOBJ_ONLINE?

How about following patch? My system cannot send EJECT notification.
So I have not tested this patch.

# Recently when I send a patch, tabs of the patch is changed to spaces often.
# So I attached the patch.

---

When hotplug.autoeject and uevents are enabled, it crashes in
kobject_uevent() since the device is no longer valid.

This patch fixes the problem.

Reported-by: Toshi Kani <toshi.kani@...com>
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>

---
  drivers/acpi/scan.c |    7 +++----
  1 file changed, 3 insertions(+), 4 deletions(-)

Index: linux-pm/drivers/acpi/scan.c
===================================================================
--- linux-pm.orig/drivers/acpi/scan.c	2013-02-22 16:02:07.000000000 +0900
+++ linux-pm/drivers/acpi/scan.c	2013-02-22 16:06:36.792816699 +0900
@@ -139,9 +139,6 @@ static int acpi_scan_hot_remove(struct a
  		"Hot-removing device %s...\n", dev_name(&device->dev)));
  
  	acpi_bus_trim(device);
-	/* Device node has been unregistered. */
-	put_device(&device->dev);
-	device = NULL;
  
  	if (ACPI_SUCCESS(acpi_get_handle(handle, "_LCK", &not_used))) {
  		arg_list.count = 1;
@@ -191,10 +188,10 @@ static void acpi_bus_device_eject(void *
  	}
  	acpi_evaluate_hotplug_ost(handle, ACPI_NOTIFY_EJECT_REQUEST,
  				  ACPI_OST_SC_EJECT_IN_PROGRESS, NULL);
+	get_device(&device->dev);
  	if (handler->hotplug.autoeject) {
  		int error;
  
-		get_device(&device->dev);
  		error = acpi_scan_hot_remove(device);
  		if (error)
  			goto err_out;
@@ -204,6 +201,7 @@ static void acpi_bus_device_eject(void *
  	if (handler->hotplug.uevents)
  		kobject_uevent(&device->dev.kobj, KOBJ_OFFLINE);
  
+	put_device(&device->dev);
   out:
  	mutex_unlock(&acpi_scan_lock);
  	return;
@@ -312,6 +310,7 @@ void acpi_bus_hot_remove_device(void *co
  					  ACPI_OST_SC_NON_SPECIFIC_FAILURE,
  					  NULL);
  
+	put_device(&acpi_device->dev);
  	mutex_unlock(&acpi_scan_lock);
  	kfree(context);
  }


View attachment "fix-panic-in-kobject_uevent.patch" of type "text/x-patch" (1713 bytes)

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