Date: Fri, 19 Nov 2010 17:03:25 -0500 From: Jung-uk Kim <jkim@FreeBSD.org> To: John Baldwin <jhb@freebsd.org> Cc: Attilio Rao <attilio@freebsd.org>, svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r215544 - head/sys/kern Message-ID: <201011191703.26742.jkim@FreeBSD.org> In-Reply-To: <201011191646.12106.jhb@freebsd.org> References: <201011191943.oAJJhv3i087205@svn.freebsd.org> <AANLkTimzP7hNYFqsYgFW4Vzuj-cOWO%2Bq9nU4vFMTJ3R=@mail.gmail.com> <201011191646.12106.jhb@freebsd.org>
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On Friday 19 November 2010 04:46 pm, John Baldwin wrote: > On Friday, November 19, 2010 4:31:44 pm Attilio Rao wrote: > > 2010/11/19 John Baldwin <jhb@freebsd.org>: > > > On Friday, November 19, 2010 4:09:28 pm Jung-uk Kim wrote: > > >> On Friday 19 November 2010 02:43 pm, Attilio Rao wrote: > > >> > Author: attilio > > >> > Date: Fri Nov 19 19:43:56 2010 > > >> > New Revision: 215544 > > >> > URL: http://svn.freebsd.org/changeset/base/215544 > > >> > > > >> > Log: > > >> > Scan the list in reverse order for the shutdown handlers > > >> > of loaded modules. This way, when there is a dependency > > >> > between two modules, the handler of the latter probed runs > > >> > first. > > >> > > > >> > This is a similar approach as the modules are unloaded in > > >> > the same linkerfile. > > >> > > > >> > Sponsored by: Sandvine Incorporated > > >> > Submitted by: Nima Misaghian <nmisaghian at sandvine > > >> > dot com> MFC after: 1 week > > >> > > >> Hmm... It is not directly related but I was thinking about > > >> doing similar things for sys/kern/subr_bus.c. What do you > > >> think about the attached patch? > > > > > > Hmm, the patches for suspend and resume that I had for this > > > took the opposite order, they did suspend in forward order, but > > > resume in backwards order. Like so: > > > > > > --- //depot/vendor/freebsd/src/sys/kern/subr_bus.c > > > 2010-11-17 22:30:24.000000000 0000 +++ > > > //depot/user/jhb/acpipci/kern/subr_bus.c 2010-11-19 > > > 17:19:02.000000000 00 @@ -3426,9 +3429,9 @@ > > > TAILQ_FOREACH(child, &dev->children, link) { > > > error = DEVICE_SUSPEND(child); > > > if (error) { > > > - for (child2 = > > > TAILQ_FIRST(&dev->children); - > > > child2 && child2 != child; - child2 > > > = TAILQ_NEXT(child2, link)) + for (child2 > > > = TAILQ_PREV(child, device_list, link); + > > > child2 != NULL; > > > + child2 = TAILQ_PREV(child2, > > > device_list, link)) DEVICE_RESUME(child2); > > > return (error); > > > } > > > @@ -3447,7 +3450,7 @@ > > > { > > > device_t child; > > > > > > - TAILQ_FOREACH(child, &dev->children, link) { > > > + TAILQ_FOREACH_REVERSE(child, &dev->children, > > > device_list, link) { DEVICE_RESUME(child); > > > /* if resume fails, there's nothing we can > > > usefully do... */ } > > > > > > (Likely mangled whitespace.) > > > > > > I couldn't convince myself which order was "more" correct for > > > suspend and resume. > > > > Considering loading in starting point, I think suspend should go > > in reverse logic and resume in the same module load logic. > > So that dependent modules are suspended first and resumed after. > > Don't you agree? > > These are devices, and the ordering here is the order of sibling > devices on a given bus. That is, if you have a PCI bus with two em > interfaces, does it really matter if em0 suspends before em1 vs > after em1? I think it actually doesn't matter. The passes from > the multipass boot probe might make some sense to order on. > However, I don't think the order of siblings on a bus is meaningful > for suspend and resume (which is why I've never committed the above > patches). > > Specifically, there is no dependency relationship between siblings > on a bus. Certain buses may in fact have a dependency order of > sorts (vgapci0 comes to mind), but those buses should manage that. > There is no generic dependency between siblings that should be > encoded into subr_bus.c Generally siblings don't interact with each other directly, no. However, some modern chipsets *do* have strong relationship. For example, some chipsets reference SMB controller to get current configuration, e.g., function A depends on function B on the same chip. Jung-uk Kim
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