linux-kernel - Re: [GIT PULL] core/urgent for v5.16-rc6

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Date:   Mon, 20 Dec 2021 08:25:37 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Borislav Petkov <bp@...e.de>,
        "Chang S. Bae" <chang.seok.bae@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86-ml <x86@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] core/urgent for v5.16-rc6

On Mon, Dec 20, 2021 at 8:20 AM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Whatever. I don't care that much, but this all smells like you just
> dug your own hole for very questionable causes, and instead of a
> "don't do that then" this all is doubling down on a bad idea.

It further looks like it's really only the sas_ss_size that is
checked, so if people wan tto have a lock, make it clear that's the
only thing that the lock is about.

So the actual "do I even need to lock" condition should likely just be

        if (ss_size < t->sas_ss_size)
                .. don't bother locking ..

but as mentioned, I don't really see much of a point in being so
careful even about the growing case.

If somebody is changing xstate features concurrently with another
thread setting up their altstack, they can keep both pieces.

                 Linus