linux-kernel - Re: [PATCH v2 28/39] timekeeping: Fix a circular include dependency

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: <b20fe713-28c6-4ca8-b64a-df017f161524@app.fastmail.com>
Date:   Fri, 27 Oct 2023 08:35:03 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Kent Overstreet" <kent.overstreet@...ux.dev>,
        "Thomas Gleixner" <tglx@...utronix.de>
Cc:     "Suren Baghdasaryan" <surenb@...gle.com>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        "Michal Hocko" <mhocko@...e.com>,
        "Vlastimil Babka" <vbabka@...e.cz>,
        "Johannes Weiner" <hannes@...xchg.org>,
        "Roman Gushchin" <roman.gushchin@...ux.dev>,
        "Mel Gorman" <mgorman@...e.de>,
        "Davidlohr Bueso" <dave@...olabs.net>,
        "Matthew Wilcox" <willy@...radead.org>,
        "Liam R. Howlett" <liam.howlett@...cle.com>,
        "Jonathan Corbet" <corbet@....net>, void@...ifault.com,
        "Peter Zijlstra" <peterz@...radead.org>, juri.lelli@...hat.com,
        ldufour@...ux.ibm.com, "Catalin Marinas" <catalin.marinas@....com>,
        "Will Deacon" <will@...nel.org>, "Ingo Molnar" <mingo@...hat.com>,
        "Dave Hansen" <dave.hansen@...ux.intel.com>, x86@...nel.org,
        peterx@...hat.com, "David Hildenbrand" <david@...hat.com>,
        "Jens Axboe" <axboe@...nel.dk>,
        "Luis Chamberlain" <mcgrof@...nel.org>,
        "Masahiro Yamada" <masahiroy@...nel.org>,
        "Nathan Chancellor" <nathan@...nel.org>, dennis@...nel.org,
        "Tejun Heo" <tj@...nel.org>, "Muchun Song" <muchun.song@...ux.dev>,
        "Mike Rapoport" <rppt@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>, pasha.tatashin@...een.com,
        yosryahmed@...gle.com, "Yu Zhao" <yuzhao@...gle.com>,
        "David Howells" <dhowells@...hat.com>,
        "Hugh Dickins" <hughd@...gle.com>,
        "Andrey Konovalov" <andreyknvl@...il.com>,
        "Kees Cook" <keescook@...omium.org>,
        "Nick Desaulniers" <ndesaulniers@...gle.com>, vvvvvv@...gle.com,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Eric Biggers" <ebiggers@...gle.com>, ytcoode@...il.com,
        "Vincent Guittot" <vincent.guittot@...aro.org>,
        dietmar.eggemann@....com, "Steven Rostedt" <rostedt@...dmis.org>,
        bsegall@...gle.com, bristot@...hat.com, vschneid@...hat.com,
        "Christoph Lameter" <cl@...ux.com>,
        "Pekka Enberg" <penberg@...nel.org>,
        "Joonsoo Kim" <iamjoonsoo.kim@....com>,
        "Hyeonggon Yoo" <42.hyeyoo@...il.com>,
        "Alexander Potapenko" <glider@...gle.com>,
        "Marco Elver" <elver@...gle.com>,
        "Dmitry Vyukov" <dvyukov@...gle.com>,
        "Shakeel Butt" <shakeelb@...gle.com>,
        "Muchun Song" <songmuchun@...edance.com>,
        "Jason Baron" <jbaron@...mai.com>,
        "David Rientjes" <rientjes@...gle.com>, minchan@...gle.com,
        kaleshsingh@...gle.com, kernel-team@...roid.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        iommu@...ts.linux.dev, Linux-Arch <linux-arch@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-modules@...r.kernel.org, kasan-dev@...glegroups.com,
        cgroups@...r.kernel.org
Subject: Re: [PATCH v2 28/39] timekeeping: Fix a circular include dependency

On Fri, Oct 27, 2023, at 01:54, Kent Overstreet wrote:
> On Fri, Oct 27, 2023 at 01:05:48AM +0200, Thomas Gleixner wrote:
>> On Thu, Oct 26 2023 at 18:33, Suren Baghdasaryan wrote:
>> > On Wed, Oct 25, 2023 at 5:33 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>> >> > This avoids a circular header dependency in an upcoming patch by only
>> >> > making hrtimer.h depend on percpu-defs.h
>> >>
>> >> What's the actual dependency problem?
>> >
>> > Sorry for the delay.
>> > When we instrument per-cpu allocations in [1] we need to include
>> > sched.h in percpu.h to be able to use alloc_tag_save(). sched.h
>> 
>> Including sched.h in percpu.h is fundamentally wrong as sched.h is the
>> initial place of all header recursions.
>> 
>> There is a reason why a lot of funtionalitiy has been split out of
>> sched.h into seperate headers over time in order to avoid that.
>
> Yeah, it's definitely unfortunate. The issue here is that
> alloc_tag_save() needs task_struct - we have to pull that in for
> alloc_tag_save() to be inline, which we really want.
>
> What if we moved task_struct to its own dedicated header? That might be
> good to do anyways...

Yes, I agree that is the best way to handle it. I've prototyped
a more thorough header cleanup with good results (much improved
build speed) in the past, and most of the work to get there is
to seperate out structures like task_struct, mm_struct, net_device,
etc into headers that only depend on the embedded structure
definitions without needing all the inline functions associated
with them.

      Arnd