linux-kernel - Re: [PATCH v3 3/3] sched, x86: Check that we're on the right stack in schedule and __might

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Message-ID: <CA+55aFwkv6+-VJM6HxgPK9eGtGtgawQO++1BDKuag+i4eoS0Ow@mail.gmail.com>
Date:	Mon, 23 May 2016 19:16:16 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Andi Kleen <andi@...stfloor.org>, Borislav Petkov <bp@...en8.de>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH v3 3/3] sched, x86: Check that we're on the right stack in
 schedule and __might_sleep

On Mon, May 23, 2016 at 7:09 PM, Andy Lutomirski <luto@...capital.net> wrote:
>
> What about this silly fix?  (Pardon the probable whitespace damage.)

That looks fine to me, and has a reason for it.

That said, I'm not convinced about the preempt_enable/preempt_disable
excuse: that would be horribly buggy anyway, and has nothing to do
with IST's. Why protect against random insane bugs?

So the "3*" certainly doesn't hurt, but and I won't argue more against
it, but it looks pretty magical and made-up. Might as well just
add/subtract one. You can never protect against people who
intentionally write buggy code, and if it's protecting against
unintentional buggy code I don't see why the IST case is so special
when it's just a tiny fraction of code..

              Linus