On Tue, Oct 06, 2015 at 06:06:50PM +0200, Peter Zijlstra wrote: > On Thu, Sep 24, 2015 at 09:21:22PM +0800, Boqun Feng wrote: > > > Included in it are some of the details on this subject, because a wakeup > > > has two prior states that are of importance, the tasks own prior state > > > and the wakeup state, both should be considered in the 'program order' > > > flow. > > > > > > > Great and very helpful ;-) > > > > > So maybe we can reduce the description in memory-barriers to this > > > 'split' program order guarantee, where a woken task must observe both > > > its own prior state and its wakee state. > > ^^^^^ > > I think you mean "waker" here, right? > > Yes. > > > And the waker is not necessarily the same task who set the @cond to > > true, right? > > It should be. > > > If so, I feel like it's really hard to *use* this 'split' > > program order guarantee in other places than sleep/wakeup itself. Could > > you give an example? Thank you. > > It was not meant to be used in any other scenario; the 'split' PO really > is part of the whole sleep/wakeup. It does not apply to anything else. Got it. So at this point, I think it's better to remove the entire "Sleep and wake-up functions" section in memory-barriers.txt. Because this order guarantee is not for other users except sleep/wakeup. Any concern, Paul? Regards, Boqun
Attachment:
signature.asc
Description: PGP signature
