On Monday, 16 July 2007 16:42, Huang, Ying wrote: > On Mon, 2007-07-16 at 14:17 +0200, Rafael J. Wysocki wrote: > > > is this a matter of running some test to find out, or is this a question > > > for the kexec implemantors? > > > > Actually, I'd like someone to tell me. ;-) > > > > I've browsed the kexec code, but haven't found anything related to the devices > > in it. Perhaps I didn't know where to look ... > > There are two stages for kexec. For "normal" kexec, first the > sys_kexe_load is called to load the kernel image, then > sys_reboot(LINUX_REBOOT_CMD_KEXEC) is called to boot the new kernel. OK, thanks. This is the information that I was missing. > The call chain is as follow: > > sys_reboot(LINUX_REBOOT_CMD_KEXEC) > kernel_kexec > kernel_restart_prepare > device_shutdown > machine_shutdown > machine_kexec > > In device_shutdown, the dev->bus->shutdown or dev->driver->shutdown of > every device is called to put device in quiescent state. In > machine_kexec, the new kernel is booted. Yes. > So, for normal kexec, there is no code path for device state saving and > restoring. Exactly. > State of device can be restore after shutdown? I don't think so. No, it can't, but we need something like this for hibernation and device_shutdown() is not appropriate for this purpose IMO. > > I think that the right approach is to separate devices' suspend from the > > devices' hibernation-related operations FIRST. Then, many different approaches > > to hibernation will be much easier to implement than they are now. > > > > I've been saying this for weeks now, but no one seems to listen frankly I'm > > tired of repeating it: > > I agree with you on this. :) OK :-) > > If we want to improve things, let's do that IN AN ORDERED WAY. If everyone > > will come up with a new idea every two days, we won't be able to get anything > > actually _done_. > > Yes, and I am very glad to collaborate with everybody who is interested > in this subject. But I think we should try to verify our idea with code > as early as possible. Now, I am trying to implement a prototype of > kexec/kdump based image writing/reading mechanism to verify the > feasibility. (I suppose you are working on separating device suspend and > device hibernate). Yes, I am. > What do you think about the pattern of collaboration? Sounds good. > At last, thank you very much for your valuable reminding in the mail of > "hibernation considerations". You're welcome. :-) Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
