kernel.git/drivers/base/power/main.c, branch linux-2.6.36.y

PM: Prevent waiting forever on asynchronous resume after failing suspend

2010-09-08T22:49:43Z

During suspend, the power.completion is expected to be set when a device has not yet started suspending. Set it on init to fix a corner case where a device is resumed when its parent has never suspended. Consider three drivers, A, B, and C. The parent of A is C, and C has async_suspend set. On boot, C->power.completion is initialized to 0. During the first suspend: suspend_devices_and_enter(...) dpm_resume(...) device_suspend(A) device_suspend(B) returns error, aborts suspend dpm_resume_end(...) dpm_resume(...) device_resume(A) dpm_wait(A->parent == C) wait_for_completion(C->power.completion) The wait_for_completion will never complete, because complete_all(C->power.completion) will only be called from device_suspend(C) or device_resume(C), neither of which is called if suspend is aborted before C. After a successful suspend->resume cycle, where B doesn't abort suspend, C->power.completion is left in the completed state by the call to device_resume(C), and the same call path will work if B aborts suspend. Signed-off-by: Colin Cross Signed-off-by: Rafael J. Wysocki

PM: Make it possible to avoid races between wakeup and system sleep

2010-07-18T23:58:48Z

One of the arguments during the suspend blockers discussion was that the mainline kernel didn't contain any mechanisms making it possible to avoid races between wakeup and system suspend. Generally, there are two problems in that area. First, if a wakeup event occurs exactly when /sys/power/state is being written to, it may be delivered to user space right before the freezer kicks in, so the user space consumer of the event may not be able to process it before the system is suspended. Second, if a wakeup event occurs after user space has been frozen, it is not generally guaranteed that the ongoing transition of the system into a sleep state will be aborted. To address these issues introduce a new global sysfs attribute, /sys/power/wakeup_count, associated with a running counter of wakeup events and three helper functions, pm_stay_awake(), pm_relax(), and pm_wakeup_event(), that may be used by kernel subsystems to control the behavior of this attribute and to request the PM core to abort system transitions into a sleep state already in progress. The /sys/power/wakeup_count file may be read from or written to by user space. Reads will always succeed (unless interrupted by a signal) and return the current value of the wakeup events counter. Writes, however, will only succeed if the written number is equal to the current value of the wakeup events counter. If a write is successful, it will cause the kernel to save the current value of the wakeup events counter and to abort the subsequent system transition into a sleep state if any wakeup events are reported after the write has returned. [The assumption is that before writing to /sys/power/state user space will first read from /sys/power/wakeup_count. Next, user space consumers of wakeup events will have a chance to acknowledge or veto the upcoming system transition to a sleep state. Finally, if the transition is allowed to proceed, /sys/power/wakeup_count will be written to and if that succeeds, /sys/power/state will be written to as well. Still, if any wakeup events are reported to the PM core by kernel subsystems after that point, the transition will be aborted.] Additionally, put a wakeup events counter into struct dev_pm_info and make these per-device wakeup event counters available via sysfs, so that it's possible to check the activity of various wakeup event sources within the kernel. To illustrate how subsystems can use pm_wakeup_event(), make the low-level PCI runtime PM wakeup-handling code use it. Signed-off-by: Rafael J. Wysocki Acked-by: Jesse Barnes Acked-by: Greg Kroah-Hartman Acked-by: markgross Reviewed-by: Alan Stern

power: support _noirq actions on device types and classes

2010-03-24T10:00:02Z

The new-style dev_pm_ops provide callbacks for both IRQs enabled and disabled. However, the _noirq variants were only called for buses registered with a device, not for classes and types. In order to properly use dev_pm_ops in class pcmcia_socket_class, support _noirq actions also on classes and types. Signed-off-by: Dominik Brodowski Acked-by: Rafael J. Wysocki

Driver core: create lock/unlock functions for struct device

2010-03-08T01:04:52Z

In the future, we are going to be changing the lock type for struct device (once we get the lockdep infrastructure properly worked out) To make that changeover easier, and to possibly burry the lock in a different part of struct device, let's create some functions to lock and unlock a device so that no out-of-core code needs to be changed in the future. This patch creates the device_lock/unlock/trylock() functions, and converts all in-tree users to them. Cc: Thomas Gleixner Cc: Jean Delvare Cc: Dave Young Cc: Ming Lei Cc: Jiri Kosina Cc: Phil Carmody Cc: Arjan van de Ven Cc: Cornelia Huck Cc: Rafael J. Wysocki Cc: Pavel Machek Cc: Len Brown Cc: Magnus Damm Cc: Alan Stern Cc: Randy Dunlap Cc: Stefan Richter Cc: David Brownell Cc: Vegard Nossum Cc: Jesse Barnes Cc: Alex Chiang Cc: Kenji Kaneshige Cc: Andrew Morton Cc: Andrew Patterson Cc: Yu Zhao Cc: Dominik Brodowski Cc: Samuel Ortiz Cc: Wolfram Sang Cc: CHENG Renquan Cc: Oliver Neukum Cc: Frans Pop Cc: David Vrabel Cc: Kay Sievers Cc: Sarah Sharp Signed-off-by: Greg Kroah-Hartman

PM: Allow device drivers to use dpm_wait()

2010-02-26T19:39:11Z

There are some dependencies between devices (in particular, between EHCI USB controllers and their OHCI/UHCI siblings) which are not reflected by the structure of the device tree. With synchronous suspend and resume these dependencies are taken into accout automatically, because the devices in question are always registered in the right order, but to meet these constraints with asynchronous suspend and resume the drivers of these devices will need to use dpm_wait() in their suspend/resume routines, so introduce a helper function allowing them to do that. Signed-off-by: Rafael J. Wysocki

PM: Start asynchronous resume threads upfront

2010-02-26T19:39:11Z

It has been shown by testing that total device resume time can be reduced significantly (by as much as 50% or more) if the async threads executing some devices' resume routines are all started before the main resume thread starts to handle the "synchronous" devices. This is a consequence of the fact that the slowest devices tend to be located at the end of dpm_list, so their resume routines are started very late. Consequently, they have to wait for all the preceding "synchronous" devices before their resume routines can be started by the main resume thread, even if they are "asynchronous". By starting their async threads upfront we effectively move those devices towards the beginning of dpm_list, without breaking their ordering with respect to their parents and children. As a result, their resume routines are started much earlier and we are able to save much more device resume time this way. Signed-off-by: Rafael J. Wysocki

PM: Add a switch for disabling/enabling asynchronous suspend/resume

2010-02-26T19:39:10Z

Add sysfs attribute /sys/power/pm_async allowing the user space to disable/enable asynchronous suspend/resume of devices. Signed-off-by: Rafael J. Wysocki

PM: Asynchronous suspend and resume of devices

2010-02-26T19:39:09Z

Theoretically, the total time of system sleep transitions (suspend to RAM, hibernation) can be reduced by running suspend and resume callbacks of device drivers in parallel with each other. However, there are dependencies between devices such that we're not allowed to suspend the parent of a device before suspending the device itself. Analogously, we're not allowed to resume a device before resuming its parent. The most straightforward way to take these dependencies into accout is to start the async threads used for suspending and resuming devices at the core level, so that async_schedule() is called for each suspend and resume callback supposed to be executed asynchronously. For this purpose, introduce a new device flag, power.async_suspend, used to mark the devices whose suspend and resume callbacks are to be executed asynchronously (ie. in parallel with the main suspend/resume thread and possibly in parallel with each other) and helper function device_enable_async_suspend() allowing one to set power.async_suspend for given device (power.async_suspend is unset by default for all devices). For each device with the power.async_suspend flag set the PM core will use async_schedule() to execute its suspend and resume callbacks. The async threads started for different devices as a result of calling async_schedule() are synchronized with each other and with the main suspend/resume thread with the help of completions, in the following way: (1) There is a completion, power.completion, for each device object. (2) Each device's completion is reset before calling async_schedule() for the device or, in the case of devices with the power.async_suspend flags unset, before executing the device's suspend and resume callbacks. (3) During suspend, right before running the bus type, device type and device class suspend callbacks for the device, the PM core waits for the completions of all the device's children to be completed. (4) During resume, right before running the bus type, device type and device class resume callbacks for the device, the PM core waits for the completion of the device's parent to be completed. (5) The PM core completes power.completion for each device right after the bus type, device type and device class suspend (or resume) callbacks executed for the device have returned. Signed-off-by: Rafael J. Wysocki

PM: Add parent information to timing messages

2010-02-26T19:39:09Z

Add parent information to the messages printed by the suspend/resume core when initcall_debug is set. Signed-off-by: Rafael J. Wysocki

power: fix kernel-doc notation

2010-01-11T17:34:06Z

Warning(drivers/base/power/main.c:453): No description found for parameter 'dev' Warning(drivers/base/power/main.c:453): No description found for parameter 'cb' Warning(drivers/base/power/main.c:719): No description found for parameter 'dev' Warning(drivers/base/power/main.c:719): No description found for parameter 'state' Warning(drivers/base/power/main.c:719): No description found for parameter 'cb' Signed-off-by: Randy Dunlap Cc: Rafael J. Wysocki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds