linux-kernel - Re: [PATCH 1/7] kthread: Don't allocate kthread

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Message-ID: <87ilqcuftz.fsf@email.froward.int.ebiederm.org>
Date:   Wed, 11 May 2022 12:41:44 -0500
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-arch@...r.kernel.org, Tejun Heo <tj@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Al Viro <viro@...IV.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>,
        Linus Torvalds <torvalds@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Максим Кутявин 
        <maximkabox13@...il.com>
Subject: Re: [PATCH 1/7] kthread: Don't allocate kthread_struct for init and
 umh

"Eric W. Biederman" <ebiederm@...ssion.com> writes:

> Thomas Gleixner <tglx@...utronix.de> writes:
>
>> I'm worried that there are more of these issues lurking. Haven't looked
>> yet.
>
> I looked earlier and I missed this one.  I am going to look again today,
> along with applying the obvious fix to task_tick_numa.

So I have just looked again and I don't see anything.  There are a
couple of subtle issues on x86.  Especially with saving floating
point but as I read the code copy_thread initializes things
properly so that code that doesn't touch floating point registers
doesn't need to do anything.

The important thing for lurking issues is that even if I missed
something practically all of the uses of PF_KTHREAD are on x86
or generic code so they should be flushed out quickly.

Eric