On Thursday, February 10, 2011, Alan Stern wrote: > On Thu, 10 Feb 2011, Ian Campbell wrote: > > > On Wed, 2011-02-09 at 23:42 +0000, Alan Stern wrote: > > > In fact there already is a "fast suspend & resume" path in the PM core. > > > It's the freeze/thaw procedure used when starting to hibernate. The > > > documentation specifically says that drivers' freeze methods are > > > supposed to quiesce their devices but not change power levels. In > > > addition, the thaw method is invoked as part of recovery from a failed > > > hibernation attempt, so it already has the "cancel" semantics that xen > > > seems to want. > > > > Sounds like that would work and I would much prefer to simply make > > correct use of the core functionality. > > It seems like a reasonable approach. Whether it will actually _work_ > is a harder question... :-) > > > So PMSG_FREEZE is balanced by either PMSG_RECOVER or PMSG_THAW depending > > on whether the suspend was cancelled or not? That's correct, but from drivers' point of view PMSG_THAW is equivalent to PMSG_RECOVER, because the both of them cause ->thaw() callbacks to be executed. > Basically yes. It is also "balanced" by PMSG_RESTORE, which is used > after a memory image has been restored (although this isn't relevant to > your snapshotting). See the comments in include/linux/pm.h. Yup. > > So the sequence of events > > is something like: > > dpm_suspend_start(PMSG_FREEZE); > > > > dpm_suspend_noirq(PMSG_FREEZE); > > > > sysdev_suspend(PMSG_QUIESCE); > > This should say sysdev_suspend(PMSG_FREEZE). Yes, PMSG_QUIESCE is restore-specific. > > cancelled = suspend_hypercall() > > At this point swsusp_arch_suspend() is called. If that translates to > suspend_hypercall() in your setting, then yes. > > > sysdev_resume(); > > > > dpm_resume_noirq(cancelled ? PMSG_RECOVER : PMSG_THAW); > > > > dpm_resume_end(cancelled ? PMSG_RECOVER : PMSG_THAW); > > ? > > Yes. Actually, I think PMSG_THAW can be used in both cases. The resume-side routines only use the 'state' argument for diagnostics. > > (For comparison we currently have: > > > > > dpm_suspend_start(PMSG_SUSPEND); > > > > > > > > > > dpm_suspend_noirq(PMSG_SUSPEND); > > > > > > > > > > sysdev_suspend(PMSG_SUSPEND); > > > > > /* suspend hypercall */ > > > > > sysdev_resume(); > > > > > > > > > > dpm_resume_noirq(PMSG_RESUME); > > > > > > > > > > dpm_resume_end(PMSG_RESUME); > > ) > > Right. The sequence of calls is the same, but the PMSG_ argument is > different so drivers are expected to act differently in response. That's correct. Thanks, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
