svn commit: r215544 - head/sys/kern

[Attilio Rao]

2010/11/19 John Baldwin <jhb at 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?

Attilio


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