lkml.org 
[lkml]   [2018]   [Jul]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCHv2 2/2] drivers/base: reorder consumer and its children behind suppliers
On Tue, Jun 26, 2018 at 7:54 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Tue, Jun 26, 2018 at 11:29:48AM +0800, Pingfan Liu wrote:
> > On Mon, Jun 25, 2018 at 6:45 PM Greg Kroah-Hartman
> > <gregkh@linuxfoundation.org> wrote:
> > >
> > > On Mon, Jun 25, 2018 at 03:47:39PM +0800, Pingfan Liu wrote:
> > > > commit 52cdbdd49853 ("driver core: correct device's shutdown order")
> > > > introduces supplier<-consumer order in devices_kset. The commit tries
> > > > to cleverly maintain both parent<-child and supplier<-consumer order by
> > > > reordering a device when probing. This method makes things simple and
> > > > clean, but unfortunately, breaks parent<-child order in some case,
> > > > which is described in next patch in this series.
> > >
> > > There is no "next patch in this series" :(
> > >
> > Oh, re-arrange the patches, and forget the comment in log
> >
> > > > Here this patch tries to resolve supplier<-consumer by only reordering a
> > > > device when it has suppliers, and takes care of the following scenario:
> > > > [consumer, children] [ ... potential ... ] supplier
> > > > ^ ^
> > > > After moving the consumer and its children after the supplier, the
> > > > potentail section may contain consumers whose supplier is inside
> > > > children, and this poses the requirement to dry out all consumpers in
> > > > the section recursively.
> > > >
> > > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > > Cc: Grygorii Strashko <grygorii.strashko@ti.com>
> > > > Cc: Christoph Hellwig <hch@infradead.org>
> > > > Cc: Bjorn Helgaas <helgaas@kernel.org>
> > > > Cc: Dave Young <dyoung@redhat.com>
> > > > Cc: linux-pci@vger.kernel.org
> > > > Cc: linuxppc-dev@lists.ozlabs.org
> > > > Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
> > > > ---
> > > > note: there is lock issue in this patch, should be fixed in next version
> > >
> > > Please send patches that you know are correct, why would I want to
> > > review this if you know it is not correct?
> > >
> > > And if the original commit is causing problems for you, why not just
> > > revert that instead of adding this much-increased complexity?
> > >
> > Revert the original commit, then it will expose the error order
> > "consumer <- supplier" again.
> > This patch tries to resolve the error and fix the following scenario:
> > step0: before the consumer device's probing, (note child_a is a
> > supplier of consumer_a, etc)
> > [ consumer-X, child_a, ...., child_z] [.... consumer_a, ...,
> > consumer_z, ....] supplier-X
> > ^^^
> > affected range during moving^^^
> > step1: When probing, moving consumer-X after supplier-X
> > [ child_a, ...., child_z] [.... consumer_a, ..., consumer_z,
> > ....] supplier-X, consumer-X
> > But it breaks "parent <-child" seq now, and should be fixed like:
> > step2:
> > [.... consumer_a, ..., consumer_z, ....] supplier-X [
> > consumer-X, child_a, ...., child_z] <---
> > descendants_reorder_after_pos() does it.
> > Again, the seq "consumer_a <- child_a" breaks the "supplier<-consumer"
> > order, should be fixed like:
> > step3:
> > [.... consumer_z, .....] supplier-X [ consumer-X, child_a,
> > consumer_a ...., child_z] <--- __device_reorder_consumer() does it.
> > ^^ affected range^^
> > The moving of consumer_a brings us to face the same scenario of step1,
> > hence we need an external recursion.
>
> Something really got messed up here, and this all does not make any
> sense :(
>
> Can you try again?
>
> Also, please cc: Rafael on all of this, as he wrote all of this
> consumer/supplier logic and I am not that familiar with it at all.
>
Cc Rafael J. Wysocki for the context. I will send out V3 soon.

Regards,
Pingfan

\
 
 \ /
  Last update: 2018-07-03 08:48    [W:0.098 / U:21.060 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site