On Tue, 27 Nov 2007, Rafael J. Wysocki wrote: > On Monday, 26 of November 2007, Pascal d'Hermilly wrote: > > When the computer suspends and comes back does it send a signal to the > > running applications? > > No, it doesn't. Applications aren't supposed to notice the suspend. Except, of course, when they need to notice the suspend. The clocks changed, the hardware configuration may have changed, and something certainly did happen, so "Applications aren't supposed to notice the suspend" is a naïve proposition at best. They need to *deal well* with it, instead. ntp needs to reset everything, for example. A LOT of software really dislikes large steps in the clocks (monotonic or gettimeofday()), and misbehave. Not notifying them they need to resync themselves is part of the breakage. Multimedia applications and screen savers are often plagued by this sort of problem. A deskptop suite trying to emulate the ThinkVantage suite in a ThinkPad might want to check that the user woke up the laptop just to eject the bay, and ask him if he wants the box to go back to sleep, and maybe even offer to do so automatically from now on. The possibilities are endless... > Your distribution surely uses some scripts that activate the kernel's suspend > code. You can modify these scripts to notify your application. Which is, of course, one way to work around the issue (and probably the best one, since trying to act upon a wakeup out-of-sync with whatever said script might be doing is likely not going to be very wise). But it would still be nice if we kicked userspace in the arse to let it know it was sleeping for a while and needs to resync, when we wake up each userspace task. The kernel makes that information available to kthreads for a damn good reason. Sounds like a job for a SIGCONT, but I don't know how well would that work. -- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
