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: Paul Martin <pm@debian.org>
Tested-by: Vojtech Gondzala <vojtech.gondzala@gmail.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Reviewed-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index d916bea..7167071 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -79,6 +79,7 @@
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 @@
{
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 @@
destroy_workqueue(kacpid_wq);
destroy_workqueue(kacpi_notify_wq);
+ destroy_workqueue(kacpi_hotplug_wq);
return AE_OK;
}
@@ -716,6 +720,7 @@
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 @@
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;
- ret = queue_work(queue, &dpc->work);
- } else {
- INIT_WORK(&dpc->work, acpi_os_execute_hp_deferred);
- ret = schedule_work(&dpc->work);
- }
+ /*
+ * 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);
if (!ret) {
printk(KERN_ERR PREFIX