Re: [PATCH] ACPI / hotplug: Fix concurrency issues and memory leaks

Rafael J. Wysocki
2013-02-13T13:12:16Z

On Wednesday, February 13, 2013 12:31:05 PM Yasuaki Ishimatsu wrote:
> Hi Rafael,
>
> I have another comment at container.c.
>
> 2013/02/13 12:08, Yasuaki Ishimatsu wrote:
> > Hi Rafael,
> >
> > The patch seems good.
> > There is a comment below.
> >
> > 2013/02/13 9:19, Rafael J. Wysocki wrote:
> >> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >>
> >> This changeset is aimed at fixing a few different but related
> >> problems in the ACPI hotplug infrastructure.
> >>
> >> First of all, since notify handlers may be run in parallel with
> >> acpi_bus_scan(), acpi_bus_trim() and acpi_bus_hot_remove_device()
> >> and some of them are installed for ACPI handles that have no struct
> >> acpi_device objects attached (i.e. before those objects are created),
> >> those notify handlers have to take acpi_scan_lock to prevent races
> >> from taking place (e.g. a struct acpi_device is found to be present
> >> for the given ACPI handle, but right after that it is removed by
> >> acpi_bus_trim() running in parallel to the given notify handler).
> >> Moreover, since some of them call acpi_bus_scan() and
> >> acpi_bus_trim(), this leads to the conclusion that acpi_scan_lock
> >> should be acquired by the callers of these two funtions rather by
> >> these functions themselves.
> >>
> >> For these reasons, make all notify handlers that can handle device
> >> addition and eject events take acpi_scan_lock and remove the
> >> acpi_scan_lock locking from acpi_bus_scan() and acpi_bus_trim().
> >> Accordingly, update all of their users to make sure that they
> >> are always called under acpi_scan_lock.
> >>
> >> Furthermore, since eject operations are carried out asynchronously
> >> with respect to the notify events that trigger them, with the help
> >> of acpi_bus_hot_remove_device(), even if notify handlers take the
> >> ACPI scan lock, it still is possible that, for example,
> >> acpi_bus_trim() will run between acpi_bus_hot_remove_device() and
> >> the notify handler that scheduled its execution and that
> >> acpi_bus_trim() will remove the device node passed to
> >> acpi_bus_hot_remove_device() for ejection. In that case, the struct
> >> acpi_device object obtained by acpi_bus_hot_remove_device() will be
> >> invalid and not-so-funny things will ensue. To protect agaist that,
> >> make the users of acpi_bus_hot_remove_device() run get_device() on
> >> ACPI device node objects that are about to be passed to it and make
> >> acpi_bus_hot_remove_device() run put_device() on them and check if
> >> their ACPI handles are not NULL (make acpi_device_unregister() clear
> >> the device nodes' ACPI handles for that check to work).
> >>
> >> Finally, observe that acpi_os_hotplug_execute() actually can fail,
> >> in which case its caller ought to free memory allocated for the
> >> context object to prevent leaks from happening. It also needs to
> >> run put_device() on the device node that it ran get_device() on
> >> previously in that case. Modify the code accordingly.
> >>
> >> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >> ---
> >>
> >> On top of linux-pm.git/linux-next.
> >>
> >> Thanks,
> >> Rafael
> >>
> >> ---
> >> drivers/acpi/acpi_memhotplug.c | 56 +++++++++++++++++++-----------
> >> drivers/acpi/container.c | 10 +++--
> >> drivers/acpi/dock.c | 19 ++++++++--
> >> drivers/acpi/processor_driver.c | 24 +++++++++---
> >> drivers/acpi/scan.c | 69 +++++++++++++++++++++++++------------
> >> drivers/pci/hotplug/acpiphp_glue.c | 6 +++
> >> drivers/pci/hotplug/sgi_hotplug.c | 5 ++
> >> include/acpi/acpi_bus.h | 3 +
> >> 8 files changed, 138 insertions(+), 54 deletions(-)
> >>
> >> Index: test/drivers/acpi/scan.c
> >> ===================================================================
> >> --- test.orig/drivers/acpi/scan.c
> >> +++ test/drivers/acpi/scan.c
> >> @@ -42,6 +42,18 @@ struct acpi_device_bus_id{
> >> struct list_head node;
> >> };
> >>
> >> +void acpi_scan_lock_acquire(void)
> >> +{
> >> + mutex_lock(&acpi_scan_lock);
> >> +}
> >> +EXPORT_SYMBOL_GPL(acpi_scan_lock_acquire);
> >> +
> >> +void acpi_scan_lock_release(void)
> >> +{
> >> + mutex_unlock(&acpi_scan_lock);
> >> +}
> >> +EXPORT_SYMBOL_GPL(acpi_scan_lock_release);
> >> +
> >> int acpi_scan_add_handler(struct acpi_scan_handler *handler)
> >> {
> >> if (!handler || !handler->attach)
> >> @@ -95,8 +107,6 @@ acpi_device_modalias_show(struct device
> >> }
> >> static DEVICE_ATTR(modalias, 0444, acpi_device_modalias_show, NULL);
> >>
> >> -static void __acpi_bus_trim(struct acpi_device *start);
> >> -
> >> /**
> >> * acpi_bus_hot_remove_device: hot-remove a device and its children
> >> * @context: struct acpi_eject_event pointer (freed in this func)
> >> @@ -107,7 +117,7 @@ static void __acpi_bus_trim(struct acpi_
> >> */
> >> void acpi_bus_hot_remove_device(void *context)
> >> {
> >> - struct acpi_eject_event *ej_event = (struct acpi_eject_event *) context;
> >> + struct acpi_eject_event *ej_event = context;
> >> struct acpi_device *device = ej_event->device;
> >> acpi_handle handle = device->handle;
> >> acpi_handle temp;
> >> @@ -118,11 +128,19 @@ void acpi_bus_hot_remove_device(void *co
> >>
> >> mutex_lock(&acpi_scan_lock);
> >>
> >> + /* If there is no handle, the device node has been unregistered. */
> >> + if (!device->handle) {
> >> + dev_dbg(&device->dev, "ACPI handle missing\n");
> >> + put_device(&device->dev);
> >> + goto out;
> >> + }
> >> +
> >> ACPI_DEBUG_PRINT((ACPI_DB_INFO,
> >> "Hot-removing device %s...\n", dev_name(&device->dev)));
> >>
> >> - __acpi_bus_trim(device);
> >> - /* Device node has been released. */
> >> + acpi_bus_trim(device);
> >> + /* Device node has been unregistered. */
> >> + put_device(&device->dev);
> >> device = NULL;
> >>
> >> if (ACPI_SUCCESS(acpi_get_handle(handle, "_LCK", &temp))) {
> >> @@ -151,6 +169,7 @@ void acpi_bus_hot_remove_device(void *co
> >> ost_code, NULL);
> >> }
> >>
> >> + out:
> >> mutex_unlock(&acpi_scan_lock);
> >> kfree(context);
> >> return;
> >> @@ -212,6 +231,7 @@ acpi_eject_store(struct device *d, struc
> >> goto err;
> >> }
> >>
> >> + get_device(&acpi_device->dev);
> >> ej_event->device = acpi_device;
> >> if (acpi_device->flags.eject_pending) {
> >> /* event originated from ACPI eject notification */
> >> @@ -224,7 +244,11 @@ acpi_eject_store(struct device *d, struc
> >> ej_event->event, ACPI_OST_SC_EJECT_IN_PROGRESS, NULL);
> >> }
> >>
> >> - acpi_os_hotplug_execute(acpi_bus_hot_remove_device, (void *)ej_event);
> >> + status = acpi_os_hotplug_execute(acpi_bus_hot_remove_device, ej_event);
> >> + if (ACPI_FAILURE(status)) {
> >> + put_device(&acpi_device->dev);
> >> + kfree(ej_event);
> >> + }
> >> err:
> >> return ret;
> >> }
> >> @@ -779,6 +803,7 @@ static void acpi_device_unregister(struc
> >> * no more references.
> >> */
> >> acpi_device_set_power(device, ACPI_STATE_D3_COLD);
> >> + device->handle = NULL;
> >> put_device(&device->dev);
> >> }
> >>
> >> @@ -1626,14 +1651,14 @@ static acpi_status acpi_bus_device_attac
> >> * there has been a real error. There just have been no suitable ACPI objects
> >> * in the table trunk from which the kernel could create a device and add an
> >> * appropriate driver.
> >> + *
> >> + * Must be called under acpi_scan_lock.
> >> */
> >> int acpi_bus_scan(acpi_handle handle)
> >> {
> >> void *device = NULL;
> >> int error = 0;
> >>
> >> - mutex_lock(&acpi_scan_lock);
> >> -
> >> if (ACPI_SUCCESS(acpi_bus_check_add(handle, 0, NULL, &device)))
> >> acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
> >> acpi_bus_check_add, NULL, NULL, &device);
> >> @@ -1644,7 +1669,6 @@ int acpi_bus_scan(acpi_handle handle)
> >> acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
> >> acpi_bus_device_attach, NULL, NULL, NULL);
> >>
> >> - mutex_unlock(&acpi_scan_lock);
> >> return error;
> >> }
> >> EXPORT_SYMBOL(acpi_bus_scan);
> >> @@ -1681,7 +1705,13 @@ static acpi_status acpi_bus_remove(acpi_
> >> return AE_OK;
> >> }
> >>
> >> -static void __acpi_bus_trim(struct acpi_device *start)
> >> +/**
> >> + * acpi_bus_trim - Remove ACPI device node and all of its descendants
> >> + * @start: Root of the ACPI device nodes subtree to remove.
> >> + *
> >> + * Must be called under acpi_scan_lock.
> >> + */
> >> +void acpi_bus_trim(struct acpi_device *start)
> >> {
> >> /*
> >> * Execute acpi_bus_device_detach() as a post-order callback to detach
> >> @@ -1698,13 +1728,6 @@ static void __acpi_bus_trim(struct acpi_
> >> acpi_bus_remove, NULL, NULL);
> >> acpi_bus_remove(start->handle, 0, NULL, NULL);
> >> }
> >> -
> >> -void acpi_bus_trim(struct acpi_device *start)
> >> -{
> >> - mutex_lock(&acpi_scan_lock);
> >> - __acpi_bus_trim(start);
> >> - mutex_unlock(&acpi_scan_lock);
> >> -}
> >> EXPORT_SYMBOL_GPL(acpi_bus_trim);
> >>
> >> static int acpi_bus_scan_fixed(void)
> >> @@ -1762,23 +1785,27 @@ int __init acpi_scan_init(void)
> >> acpi_csrt_init();
> >> acpi_container_init();
> >>
> >> + mutex_lock(&acpi_scan_lock);
> >> /*
> >> * Enumerate devices in the ACPI namespace.
> >> */
> >> result = acpi_bus_scan(ACPI_ROOT_OBJECT);
> >> if (result)
> >> - return result;
> >> + goto out;
> >>
> >> result = acpi_bus_get_device(ACPI_ROOT_OBJECT, &acpi_root);
> >> if (result)
> >> - return result;
> >> + goto out;
> >>
> >> result = acpi_bus_scan_fixed();
> >> if (result) {
> >> acpi_device_unregister(acpi_root);
> >> - return result;
> >> + goto out;
> >> }
> >>
> >> acpi_update_all_gpes();
> >> - return 0;
> >> +
> >> + out:
> >> + mutex_unlock(&acpi_scan_lock);
> >> + return result;
> >> }
> >> Index: test/include/acpi/acpi_bus.h
> >> ===================================================================
> >> --- test.orig/include/acpi/acpi_bus.h
> >> +++ test/include/acpi/acpi_bus.h
> >> @@ -395,6 +395,9 @@ int acpi_bus_receive_event(struct acpi_b
> >> static inline int acpi_bus_generate_proc_event(struct acpi_device *device, u8 type, int data)
> >> { return 0; }
> >> #endif
> >> +
> >> +void acpi_scan_lock_acquire(void);
> >> +void acpi_scan_lock_release(void);
> >> int acpi_scan_add_handler(struct acpi_scan_handler *handler);
> >> int acpi_bus_register_driver(struct acpi_driver *driver);
> >> void acpi_bus_unregister_driver(struct acpi_driver *driver);
> >> Index: test/drivers/acpi/acpi_memhotplug.c
> >> ===================================================================
> >> --- test.orig/drivers/acpi/acpi_memhotplug.c
> >> +++ test/drivers/acpi/acpi_memhotplug.c
> >> @@ -153,14 +153,16 @@ acpi_memory_get_device_resources(struct
> >> return 0;
> >> }
> >>
> >> -static int
> >> -acpi_memory_get_device(acpi_handle handle,
> >> - struct acpi_memory_device **mem_device)
> >> +static int acpi_memory_get_device(acpi_handle handle,
> >> + struct acpi_memory_device **mem_device)
> >> {
> >> struct acpi_device *device = NULL;
> >> - int result;
> >> + int result = 0;
> >> +
> >> + acpi_scan_lock_acquire();
> >>
> >> - if (!acpi_bus_get_device(handle, &device) && device)
> >> + acpi_bus_get_device(handle, &device);
> >> + if (device)
> >> goto end;
> >>
> >> /*
> >> @@ -169,23 +171,28 @@ acpi_memory_get_device(acpi_handle handl
> >> */
> >> result = acpi_bus_scan(handle);
> >> if (result) {
> >> - acpi_handle_warn(handle, "Cannot add acpi bus\n");
> >> - return -EINVAL;
> >> + acpi_handle_warn(handle, "ACPI namespace scan failed\n");
> >> + result = -EINVAL;
> >> + goto out;
> >> }
> >> result = acpi_bus_get_device(handle, &device);
> >> if (result) {
> >> acpi_handle_warn(handle, "Missing device object\n");
> >> - return -EINVAL;
> >> + result = -EINVAL;
> >> + goto out;
> >> }
> >>
> >> - end:
> >> + end:
> >> *mem_device = acpi_driver_data(device);
> >> if (!(*mem_device)) {
> >> dev_err(&device->dev, "driver data not found\n");
> >> - return -ENODEV;
> >> + result = -ENODEV;
> >> + goto out;
> >> }
> >>
> >> - return 0;
> >> + out:
> >> + acpi_scan_lock_release();
> >> + return result;
> >> }
> >>
> >> static int acpi_memory_check_device(struct acpi_memory_device *mem_device)
> >> @@ -305,6 +312,7 @@ static void acpi_memory_device_notify(ac
> >> struct acpi_device *device;
> >> struct acpi_eject_event *ej_event = NULL;
> >> u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
> >> + acpi_status status;
> >>
> >> switch (event) {
> >> case ACPI_NOTIFY_BUS_CHECK:
> >> @@ -327,29 +335,40 @@ static void acpi_memory_device_notify(ac
> >> ACPI_DEBUG_PRINT((ACPI_DB_INFO,
> >> "\nReceived EJECT REQUEST notification for device\n"));
> >>
> >> + status = AE_ERROR;
> >> + acpi_scan_lock_acquire();
> >> +
> >> if (acpi_bus_get_device(handle, &device)) {
> >> acpi_handle_err(handle, "Device doesn't exist\n");
> >> - break;
> >> + goto unlock;
> >> }
> >> mem_device = acpi_driver_data(device);
> >> if (!mem_device) {
> >> acpi_handle_err(handle, "Driver Data is NULL\n");
> >> - break;
> >> + goto unlock;
> >> }
> >>
> >> ej_event = kmalloc(sizeof(*ej_event), GFP_KERNEL);
> >> if (!ej_event) {
> >> pr_err(PREFIX "No memory, dropping EJECT\n");
> >> - break;
> >> + goto unlock;
> >> }
> >>
> >> + get_device(&device->dev);
> >> ej_event->device = device;
> >> ej_event->event = ACPI_NOTIFY_EJECT_REQUEST;
> >> - acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
> >> - (void *)ej_event);
> >> + /* The eject is carried out asynchronously. */
> >> + status = acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
> >> + ej_event);
> >> + if (ACPI_FAILURE(status)) {
> >> + put_device(&device->dev);
> >> + kfree(ej_event);
> >> + }
> >>
> >> - /* eject is performed asynchronously */
> >> - return;
> >> + unlock:
> >> + acpi_scan_lock_release();
> >> + if (ACPI_SUCCESS(status))
> >> + return;
> >> default:
> >> ACPI_DEBUG_PRINT((ACPI_DB_INFO,
> >> "Unsupported event [0x%x]\n", event));
> >> @@ -360,7 +379,6 @@ static void acpi_memory_device_notify(ac
> >>
> >> /* Inform firmware that the hotplug operation has completed */
> >> (void) acpi_evaluate_hotplug_ost(handle, event, ost_code, NULL);
> >> - return;
> >> }
> >>
> >> static void acpi_memory_device_free(struct acpi_memory_device *mem_device)
> >> Index: test/drivers/acpi/processor_driver.c
> >> ===================================================================
> >> --- test.orig/drivers/acpi/processor_driver.c
> >> +++ test/drivers/acpi/processor_driver.c
> >> @@ -683,8 +683,11 @@ static void acpi_processor_hotplug_notif
> >> struct acpi_device *device = NULL;
> >> struct acpi_eject_event *ej_event = NULL;
> >> u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
> >> + acpi_status status;
> >> int result;
> >>
> >> + acpi_scan_lock_acquire();
> >> +
> >> switch (event) {
> >> case ACPI_NOTIFY_BUS_CHECK:
> >> case ACPI_NOTIFY_DEVICE_CHECK:
> >> @@ -733,25 +736,32 @@ static void acpi_processor_hotplug_notif
> >> break;
> >> }
> >>
> >> + get_device(&device->dev);
> >> ej_event->device = device;
> >> ej_event->event = ACPI_NOTIFY_EJECT_REQUEST;
> >> - acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
> >> - (void *)ej_event);
> >> -
> >> - /* eject is performed asynchronously */
> >> - return;
> >> + /* The eject is carried out asynchronously. */
> >> + status = acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
> >> + ej_event);
> >> + if (ACPI_FAILURE(status)) {
> >> + put_device(&device->dev);
> >> + kfree(ej_event);
> >> + break;
> >> + }
> >> + goto out;
> >>
> >> default:
> >> ACPI_DEBUG_PRINT((ACPI_DB_INFO,
> >> "Unsupported event [0x%x]\n", event));
> >>
> >> /* non-hotplug event; possibly handled by other handler */
> >> - return;
> >> + goto out;
> >> }
> >>
> >> /* Inform firmware that the hotplug operation has completed */
> >> (void) acpi_evaluate_hotplug_ost(handle, event, ost_code, NULL);
> >> - return;
> >> +
> >> + out:
> >
> >> + acpi_scan_lock_release();;
> >
> > extra ";"
> >
> > Thanks,
> > Yasuaki Ishimatsu
> >
> >> }
> >>
> >> static acpi_status is_processor_device(acpi_handle handle)
> >> Index: test/drivers/acpi/container.c
> >> ===================================================================
> >> --- test.orig/drivers/acpi/container.c
> >> +++ test/drivers/acpi/container.c
> >> @@ -88,6 +88,8 @@ static void container_notify_cb(acpi_han
> >> acpi_status status;
> >> u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
> >>
> >> + acpi_scan_lock_acquire();
> >> +
> >> switch (type) {
> >> case ACPI_NOTIFY_BUS_CHECK:
> >> /* Fall through */
>
> 101 present = is_device_present(handle);
> 102 status = acpi_bus_get_device(handle, &device);
> 103 if (!present) {
> 104 if (ACPI_SUCCESS(status)) {
> 105 /* device exist and this is a remove request */
> 106 device->flags.eject_pending = 1;
> 107 kobject_uevent(&device->dev.kobj, KOBJ_OFLINE);
>
> 108 return;
>
> It should use "goto out" instead of return.
>
> 109 }
> 110 break;
> 111 }

Indeed, I have overlooked that. Thanks for spotting it!

I'll send an update with this issue fixed (and your comment from the previous
message addressed) shortly.

Thanks,
Rafael

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.