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The system wakeup framework is not very consistent with respect to the way it handles suspend-to-idle and generally wakeup events occurring during transitions to system low-power states. First off, system transitions in progress are aborted by the event reporting helpers like pm_wakeup_event() only if the wakeup_count sysfs attribute is in use (as documented), but there are cases in which system-wide transitions should be aborted even if that is not the case. For example, a wakeup signal from a designated wakeup device during system-wide PM transition, it should cause the transition to be aborted right away. Moreover, there is a freeze_wake() call in wakeup_source_activate(), but that really is only effective after suspend_freeze_state has been set to FREEZE_STATE_ENTER by freeze_enter(). However, it is very unlikely that wakeup_source_activate() will ever be called at that time, as it could only be triggered by a IRQF_NO_SUSPEND interrupt handler, so wakeups from suspend-to-idle don't really occur in wakeup_source_activate(). At the same time there is a way to abort a system suspend in progress (or wake up the system from suspend-to-idle), which is by calling pm_system_wakeup(), but in turn that doesn't cause any wakeup source objects to be activated, so it will not be covered by wakeup source statistics and will not prevent the system from suspending again immediately (in case autosleep is used, for example). Consequently, if anyone wants to abort system transitions in progress and allow the wakeup_count mechanism to work, they need to use both pm_system_wakeup() and pm_wakeup_event(), say, at the same time which is awkward. For the above reasons, make it possible to trigger pm_system_wakeup() from within wakeup_source_activate() and provide a new pm_wakeup_hard_event() helper to do so within the wakeup framework. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> |
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README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.