linux-kernel - Re: [GIT PULL] VFIO fixes for v4.1-rc2

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Message-ID: <CA+55aFziVpH1qyf8M+GdJxh3oJWd84pdJbo94kuMfSi1QscLew@mail.gmail.com>
Date:	Fri, 1 May 2015 11:37:24 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Alex Williamson <alex.williamson@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	kvm <kvm@...r.kernel.org>
Subject: Re: [GIT PULL] VFIO fixes for v4.1-rc2

On Fri, May 1, 2015 at 10:40 AM, Alex Williamson
<alex.williamson@...hat.com> wrote:
>
> - Flush signals on interrupted wait to retain polling interval (Alex Williamson)

This cannot *possibly* be right. If I read this patch right, you're
randomly just getting rid of signals. No way in hell is that correct.

"flush_signals()" is only for kernel threads, where it's a hacky
alternative to actually handling them (since kernel threads never
rreturn to user space and cannot really "handle" a signal). But you're
doing it in the ->remove handler for the device, which can be called
by arbitrary system processes. This is not a kernel thread thing, as
far as I can see.

If you cannot handle signals, you damn well shouldn't be using
"wait_event_interruptible_timeout()" to begin with. Get rid of the
"interruptible", since it apparently *isn't* interruptible.

So I'm not pulling this.

Now I'm worried that other drivers do insane things like this. I
wonder if we should add some sanity test to flush_signals() to make
sure that it can only ever get called from a kernel thread.

Oleg?

                          Linus
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