linux-kernel - Re: [PATCH 1/6] clk: Remove recursion in clk_core

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <154038647375.53599.631725372765617195@swboyd.mtv.corp.google.com>
Date:   Wed, 24 Oct 2018 06:07:53 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Derek Basehore <dbasehore@...omium.org>,
        linux-kernel@...r.kernel.org
Cc:     linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-doc@...r.kernel.org,
        mturquette@...libre.com, heiko@...ech.de, aisheng.dong@....com,
        mchehab+samsung@...nel.org, corbet@....net,
        Stephen Boyd <sboyd@...eaurora.org>,
        Jerome Brunet <jbrunet@...libre.com>,
        Derek Basehore <dbasehore@...omium.org>
Subject: Re: [PATCH 1/6] clk: Remove recursion in clk_core_{prepare,enable}()

Quoting Derek Basehore (2018-10-23 18:31:27)
> From: Stephen Boyd <sboyd@...eaurora.org>
> 
> Enabling and preparing clocks can be written quite naturally with
> recursion. We start at some point in the tree and recurse up the
> tree to find the oldest parent clk that needs to be enabled or
> prepared. Then we enable/prepare and return to the caller, going
> back to the clk we started at and enabling/preparing along the
> way.
> 
> The problem is recursion isn't great for kernel code where we
> have a limited stack size. Furthermore, we may be calling this
> code inside clk_set_rate() which also has recursion in it, so
> we're really not looking good if we encounter a tall clk tree.
> 
> Let's create a stack instead by looping over the parent chain and
> collecting clks of interest. Then the enable/prepare becomes as
> simple as iterating over that list and calling enable.
> 
> Cc: Jerome Brunet <jbrunet@...libre.com>
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> Signed-off-by: Derek Basehore <dbasehore@...omium.org>

Did you change anything substantially? Or is it just a resend of my
patch from a while ago? If you can add a link to the original and also
describe what changed in a maintainer tag it would be much easier for me
to compare.