linux-kernel - Re: [PATCH] signals: Generate warning when flush_signals() is called from non-kthread context

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Date:	Thu, 7 May 2015 15:33:53 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Oleg Nesterov <oleg@...hat.com>
cc:	NeilBrown <neilb@...e.de>, Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Evgeniy Polyakov <zbr@...emap.net>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	Alex Williamson <alex.williamson@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	kvm <kvm@...r.kernel.org>
Subject: Re: [PATCH] signals: Generate warning when flush_signals() is called
 from non-kthread context

On Mon, 4 May 2015, Oleg Nesterov wrote:

> > All the calls in md.c are in a kernel thread so safe, but I'd rather have an
> > explicit "uninterruptible, but no load-average" wait....
> 
> Could you please explain why md_thread() does allow_signal(SIGKILL) ?
> 
> I am just curious. It looks as if we want to allow user-space to "call"
> thread->run(), and this looks strange.

One would think that this is because md wants to be notified when system 
is going to be halted/rebooted, and userspace init (whatever that is) 
decides to do 'kill -9 -1' to perform the final shutdown of md (the 
question is why it really should be needed, becasue all filesystems should 
be R/O by that time anyway).

-- 
Jiri Kosina
SUSE Labs

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