linux-kernel - Re: [PATCH v3 1/1] kthread: allocate kthread structure using kmalloc

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Message-ID: <20161026155155.GA28832@redhat.com>
Date:   Wed, 26 Oct 2016 17:51:56 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Roman Pen <roman.penyaev@...fitbricks.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/1] kthread: allocate kthread structure using
        kmalloc

On 10/26, Thomas Gleixner wrote:
>
> On Wed, 26 Oct 2016, Oleg Nesterov wrote:
> > +static inline void set_kthread_struct(void *kthread)
> > +{
> > +	/*
> > +	 * We abuse ->set_child_tid to avoid the new member and because it
> > +	 * can't be wrongly copied by copy_process(). We also rely on fact
> > +	 * that the caller can't exec, so PF_KTHREAD can't be cleared.
> > +	 */
> > +	current->set_child_tid = (__force void __user *)kthread;
>
> Can we pretty please avoid this type casting? We only have 5 places using
> set_child_tid. So we can really make it a proper union

Yes, I thought about anonymous union too, the only problem is that
it will need more comments ;)

And I agree with other nits, will redo/resend tomorrow.

Thanks!

Oleg.