linux-kernel - Re: thermal zones break with patch "Reimplement IDR and IDA using the radix tree" (mainline+next)

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Date:   Mon, 19 Dec 2016 19:56:53 -0800
From:   Eduardo Valentin <edubezval@...il.com>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     Matthew Wilcox <mawilcox@...rosoft.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Zhang Rui <rui.zhang@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: thermal zones break with patch "Reimplement IDR and IDA using
 the radix tree" (mainline+next)

Hey,

On Sat, Dec 17, 2016 at 01:48:33AM +0100, Heiko Stuebner wrote:
> Hi Matthew,
> 
> Am Freitag, 16. Dezember 2016, 21:19:37 CET schrieb Matthew Wilcox:
> > From: Heiko Stuebner [mailto:heiko@...ech.de]
> > 
> > > commit b05bbe3ea2db ("Reimplement IDR and IDA using the radix tree")
> > > seems to
> > > break thermal zone allocation. This happens both on todays mainline and
> > > linux-next-20161216 and produces errors like:
> > 
> > 
> > 
> > > While I haven't looked to deeply into what idr exactly does, some
> > > findings:
>  - thermal_zone0 and thermal_zone1 are allocated correctly
> > > - every further thermal_zone always gets allocated the number "1"
> > > - thermal core calls idr_alloc with 0 for both start and end
> > > - the rewrite-patch seems to change the semantics of idr_alloc
> > > 
> > >   where it orignally said "@end: the maximum id (exclusive, <= 0 for
> > >   max)"
> > >   the "<= 0" part is gone now, but I checked, simply setting INT_MAX
> > >   as end in the thermal_core does not help
> > 
> > 
> > Hi Heiko,
> > 
> > Thanks for the report!  The problem is because the thermal subsystem calls
> > idr_alloc() passing a NULL pointer for the data.  I have fixed this problem
> > in my git tree but haven't sent the patch to Andrew yet.  This patch should
> > fix the problem for you:
>  
> > http://git.infradead.org/users/willy/linux-dax.git/commitdiff/c52eeed7b759c3
> > fefe9b7f1b0a17a438df6950f3
> 
> yay, this fixes the issue. This should definitly go as fix into 4.10-rc and when 
> you send it to Andrew you can add my
> 
> Tested-by: Heiko Stuebner <heiko@...ech.de>
> 
>  
> > Now ... thermal is actually using an IDR when it could save memory by using
> > an IDA.  Are you interested in doing that conversion?
> 
> That would more be a question for Eduardo and Rui :-) . I'm just in the 
> process of tracking down the smallish issues on my Rockchip board that are 
> poping up during the merge-window.

I would prefer to get the right implementation, and fixing thermal core by using IDA.

But given that this touches thermal core, we need an agreement with Rui
too.

> 
> 
> Anyway, thanks for pointing to the fix
> Heiko