On Monday, June 28, 2010, mark gross wrote: > Looks good to me! Great, thanks! May I add your "Acked-by" to the patch, then? Rafael > On Sat, Jun 26, 2010 at 03:14:13PM +0200, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki <rjw@xxxxxxx> > > > > One of the arguments during the suspend blockers discussion was that > > the mainline kernel didn't contain any mechanisms making it possible > > to avoid losing wakeup events during 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 <rjw@xxxxxxx> > > --- -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
