Messages in this thread | | | Date | Mon, 16 Jul 2007 21:18:32 -0700 (PDT) | From | david@lang ... | Subject | Re: [PATCH 0/2] Kexec jump: The first step to kexec base hibernation |
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On Mon, 16 Jul 2007, Rafael J. Wysocki wrote:
> 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.
is the only reason that device_shutdown() is not appropriate the amount of time it takes to shutdown some devices and then start them up again? (I'm specificly thinking of drive spin down/up as an example)
if so, it is probably worth implementing a demo with the long times involved to hash out any other problems, and then implemnt shortcuts to avoid the device_shutdown only where the time involved is excessive.
so, exactly where in the process above does the memory map need to be created? is this in the machine_shutdown step or would it need to be in the machine_kexec step?
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