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Commit c02256be authored by Zhang Rui's avatar Zhang Rui Committed by Len Brown
Browse files

ACPI: fix a deadlock in hotplug case 

we used to run the hotplug code in keventd_wq.
But when hot removing the ACPI battery device,
power_supply_unregister invokes flush_scheduled_work.
This causes a deadlock. i.e
1. When dock is unplugged, all the hotplug code is run on kevent_wq.
2. the hotplug code removes all the child devices of dock device.
3. removing the child device may invoke flush_scheduled_work
4. flush_scheduled_work waits until all the work on kevent_wq to be
   finished, while this will never be true because the hotplug code
   is running on keventd_wq...

Introduce a new workqueue for hotplug in this patch.
http://bugzilla.kernel.org/show_bug.cgi?id=13533



Tested-by: default avatarPaul Martin <pm@debian.org>
Tested-by: default avatarVojtech Gondzala <vojtech.gondzala@gmail.com>
Signed-off-by: default avatarZhang Rui <rui.zhang@intel.com>
Reviewed-by: default avatarBjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent 07a2039b

drivers/acpi/osl.c

+16 −9
Original line number Diff line number Diff line
@@ -79,6 +79,7 @@ static acpi_osd_handler acpi_irq_handler; 
static void *acpi_irq_context;

static struct workqueue_struct *kacpid_wq;

static struct workqueue_struct *kacpi_notify_wq;

static struct workqueue_struct *kacpi_hotplug_wq;



struct acpi_res_list {

	resource_size_t start;
@@ -192,8 +193,10 @@ acpi_status acpi_os_initialize1(void) 
{

	kacpid_wq = create_singlethread_workqueue("kacpid");

	kacpi_notify_wq = create_singlethread_workqueue("kacpi_notify");

	kacpi_hotplug_wq = create_singlethread_workqueue("kacpi_hotplug");

	BUG_ON(!kacpid_wq);

	BUG_ON(!kacpi_notify_wq);

	BUG_ON(!kacpi_hotplug_wq);

	return AE_OK;

}
@@ -206,6 +209,7 @@ acpi_status acpi_os_terminate(void) 


	destroy_workqueue(kacpid_wq);

	destroy_workqueue(kacpi_notify_wq);

	destroy_workqueue(kacpi_hotplug_wq);



	return AE_OK;

}
@@ -716,6 +720,7 @@ static acpi_status __acpi_os_execute(acpi_execute_type type, 
	acpi_status status = AE_OK;

	struct acpi_os_dpc *dpc;

	struct workqueue_struct *queue;

	work_func_t func;

	int ret;

	ACPI_DEBUG_PRINT((ACPI_DB_EXEC,

			  "Scheduling function [%p(%p)] for deferred execution.\n",
@@ -740,15 +745,17 @@ static acpi_status __acpi_os_execute(acpi_execute_type type, 
	dpc->function = function;

	dpc->context = context;



	if (!hp) {

		INIT_WORK(&dpc->work, acpi_os_execute_deferred);

		queue = (type == OSL_NOTIFY_HANDLER) ?

			kacpi_notify_wq : kacpid_wq;

	/*

	 * We can't run hotplug code in keventd_wq/kacpid_wq/kacpid_notify_wq

	 * because the hotplug code may call driver .remove() functions,

	 * which invoke flush_scheduled_work/acpi_os_wait_events_complete

	 * to flush these workqueues.

	 */

	queue = hp ? kacpi_hotplug_wq :

		(type == OSL_NOTIFY_HANDLER ? kacpi_notify_wq : kacpid_wq);

	func = hp ? acpi_os_execute_hp_deferred : acpi_os_execute_deferred;

	INIT_WORK(&dpc->work, func);

	ret = queue_work(queue, &dpc->work);

	} else {

		INIT_WORK(&dpc->work, acpi_os_execute_hp_deferred);

		ret = schedule_work(&dpc->work);

	}



	if (!ret) {

		printk(KERN_ERR PREFIX