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Date: Mon, 3 Aug 2009 23:26:02 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Zhang Rui <rui.zhang@...el.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"linux-pm" <linux-pm@...ts.linux-foundation.org>,
"linux-acpi" <linux-acpi@...r.kernel.org>,
Pavel Machek <pavel@....cz>, Len Brown <lenb@...nel.org>,
Alan Stern <stern@...land.harvard.edu>,
Arjan van de Ven <arjan@...ux.intel.com>, dtor@...l.ru
Subject: Re: [PATCH V2 2/4] introduce the device async action mechanism
On Friday 24 July 2009, Zhang Rui wrote:
> Introduce Device Async Action Mechanism
>
> In order to speed up Linux suspend/resume/shutdown process,
> we introduce the device async action mechanism that allow devices
> to suspend/resume/shutdown asynchronously.
>
> The basic idea is that,
> if the suspend/resume/shutdown process of a device group,
> including a root device and its child devices, are independent of
> other devices, we create an async domain for this device group,
> and make them suspend/resume/shutdown asynchronously.
>
> Note that DEV_ASYNC_RESUME is different from DEV_ASYNC_SUSPEND and
> DEV_ASYNC_SHUTDOWN.
> In resume case, all the parents are resumed first.
> deferred resuming of the child devices won't break anything.
> So it's easy to find out a device group that supports DEV_ASYNC_RESUME.
>
> In suspend/shutdown case, child devices should be suspended/shutdown
> before the parents. But deferred suspend/shutdown may break this rule.
> so for a device groups that supports DEV_ASYNC_SUSPEND&DEV_ASYNC_SHUTDOWN,
> the root device of this device async group must NOT depend on its parents.
> i.e. it's fully functional without its parents.
> e.g. I create a device async group for i8042 controller in patch 4,
> and the parent of i8042 controller device is the "platform" device under
> sysfs root device.
For general comments, please refer to my reply to the [0/4] message. Some
coding-related remarks are below.
> Signed-off-by: Zhang Rui <rui.zhang@...el.com>
> ---
> drivers/base/Makefile | 3
> drivers/base/async_dev.c | 199 ++++++++++++++++++++++++++++++++++++++++++++++
> drivers/base/core.c | 35 ++++++--
> drivers/base/power/main.c | 24 +++++
> include/linux/async_dev.h | 47 ++++++++++
> include/linux/device.h | 2
> 6 files changed, 298 insertions(+), 12 deletions(-)
>
> Index: linux-2.6/drivers/base/Makefile
> ===================================================================
> --- linux-2.6.orig/drivers/base/Makefile
> +++ linux-2.6/drivers/base/Makefile
> @@ -3,7 +3,8 @@
> obj-y := core.o sys.o bus.o dd.o \
> driver.o class.o platform.o \
> cpu.o firmware.o init.o map.o devres.o \
> - attribute_container.o transport_class.o
> + attribute_container.o transport_class.o \
> + async_dev.o
> obj-y += power/
> obj-$(CONFIG_HAS_DMA) += dma-mapping.o
> obj-$(CONFIG_ISA) += isa.o
> Index: linux-2.6/drivers/base/async_dev.c
> ===================================================================
> --- /dev/null
> +++ linux-2.6/drivers/base/async_dev.c
> @@ -0,0 +1,199 @@
> +/*
> + * async_dev.c: Device asynchronous functions
> + *
> + * (C) Copyright 2009 Intel Corporation
> + * Author: Zhang Rui <rui.zhang@...el.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; version 2
> + * of the License.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/async.h>
> +#include <linux/async_dev.h>
> +
> +static LIST_HEAD(dev_async_list);
> +static int dev_async_enabled;
> +
> +struct dev_async_context {
> + struct device *dev;
> + void *data;
> + void *func;
> +};
Please, _please_ don't use (void * ) for passing function pointers. IMO doing
that is fundamentally wrong.
> +static int dev_action(struct device *dev, dev_async_func func,
> + void *data)
> +{
> + int error = 0;
> +
> + if (!func || !dev)
> + return -EINVAL;
> +
> + error = func(dev, data);
> +
> + return error;
> +}
Hmm, what about:
+ return func && dev ? func(dev, data) : -EINVAL;
That gives you a one-liner, doesn't it?
> +static void dev_async_action(void *data, async_cookie_t cookie)
> +{
> + int error;
> + struct dev_async_context *context = data;
> +
> + context->dev->dev_async->cookie = cookie;
> + async_synchronize_cookie_domain(cookie,
> + &context->dev->dev_async->domain);
> +
> + error = dev_action(context->dev, context->func, context->data);
> + if (error)
> + printk(KERN_ERR "PM: Device %s async action failed: error %d\n",
> + dev_name(context->dev), error);
> +
> + kfree(context);
> +}
> +
> +/**
> + * dev_async_schedule - async execution of device actions.
> + * @dev: Device.
> + * @func: device callback function.
> + * @data: data.
> + * @type: the type of device async actions.
> + */
> +int dev_async_schedule(struct device *dev, dev_async_func func,
> + void *data, int type)
> +{
> + struct dev_async_context *context;
> +
> + if (!func || !dev)
> + return -EINVAL;
> +
> + if (!(type & DEV_ASYNC_ACTIONS_ALL))
> + return -EINVAL;
> +
> + if (!dev_async_enabled || !dev->dev_async)
> + return dev_action(dev, func, data);
> +
> + /* device doesn't support the current async action */
> + if (!(dev->dev_async->type & type))
> + return dev_action(dev, func, data);
> +
> + context = kzalloc(sizeof(struct dev_async_context), GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + context->dev = dev;
> + context->data = data;
> + context->func = func;
> + async_schedule_domain(dev_async_action, context,
> + &dev->dev_async->domain);
> + return 0;
> +}
> +
> +/**
> + * device_async_synchronization - sync point for all the async actions
> + * @dev: Device.
> + *
> + * wait until all the async actions are done.
> + */
> +void dev_async_synchronization(void)
> +{
> + struct dev_async_struct *pos;
> +
> + list_for_each_entry(pos, &dev_async_list, node)
> + async_synchronize_full_domain(&pos->domain);
> +
> + return;
What the return statement is for?
> +}
> +
> +static int dev_match(struct device *dev, void *data)
> +{
> + dev_err(dev->parent, "Child device %s is registered before "
> + "dev->dev_async being initialized", dev_name(dev));
> + return 1;
> +}
> +
> +/**
> + * device_async_register - register a device that supports async actions
> + * @dev: Device.
> + * @type: the kind of dev async actions that supported
> + *
> + * Register a device that supports a certain kind of dev async actions.
> + * Create a synchrolization Domain for this device and share with all its
> + * child devices.
> + */
> +int dev_async_register(struct device *dev, int type)
> +{
> + if (!dev_async_enabled)
> + return 0;
> +
> + if (!dev)
> + return -EINVAL;
> +
> + if (dev->dev_async) {
> + /* multiple async domains for a single device not supported */
> + dev_err(dev, "async domain already registered\n");
> + return -EEXIST;
> + }
> +
> + /*
> + * dev_async_register must be called before any of its child devices
> + * being registered to the driver model.
> + */
> + if (dev->p)
> + if (device_find_child(dev, NULL, dev_match)) {
> + dev_err(dev, "Can not register device async domain\n");
> + return -EINVAL;
> + }
> +
> + /* check for unsupported async actions */
> + if (!(type & DEV_ASYNC_ACTIONS_ALL)) {
> + dev_err(dev, "unsupported async action %x registered\n", type);
> + return -EINVAL;
> + }
> +
> + dev->dev_async = kzalloc(sizeof(struct dev_async_struct), GFP_KERNEL);
> + if (!dev->dev_async)
> + return -ENOMEM;
> +
> + INIT_LIST_HEAD(&dev->dev_async->domain);
> + dev->dev_async->dev = dev;
> + dev->dev_async->type = type;
> + list_add_tail(&dev->dev_async->node, &dev_async_list);
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(dev_async_register);
> +
> +/**
> + * device_async_unregister - unregister a device that supports async actions
> + * @dev: Device.
> + *
> + * Unregister a device that supports async actions.
> + * And delete async action Domain at the same time.
> + */
> +void dev_async_unregister(struct device *dev)
> +{
> + if (!dev_async_enabled)
> + return;
> +
> + if (!dev->dev_async)
> + return;
> +
> + if (dev->dev_async->dev != dev)
> + return;
> +
> + list_del(&dev->dev_async->node);
> + kfree(dev->dev_async);
> + dev->dev_async = NULL;
> + return;
And here?
Well, it looks like my comments to the previous version of the patch were
silently ignored. :-(
Best,
Rafael
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