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

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Date:   Fri, 16 Dec 2016 21:19:37 +0000
From:   Matthew Wilcox <mawilcox@...rosoft.com>
To:     Heiko Stuebner <heiko@...ech.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>
CC:     "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)

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/c52eeed7b759c3fefe9b7f1b0a17a438df6950f3

Now ... thermal is actually using an IDR when it could save memory by using an IDA.  Are you interested in doing that conversion?