linux-kernel - Re: [RFC PATCH 00/18] kthreads/signal: Safer kthread API and signal handling

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Date:	Wed, 17 Jun 2015 04:34:50 -0700
From:	Christoph Hellwig <hch@...radead.org>
To:	Petr Mladek <pmladek@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Richard Weinberger <richard@....at>,
	Steven Rostedt <rostedt@...dmis.org>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-mtd@...ts.infradead.org,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Anna Schumaker <anna.schumaker@...app.com>,
	linux-nfs@...r.kernel.org, Chris Mason <clm@...com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...e.de>,
	Michal Hocko <mhocko@...e.cz>, live-patching@...r.kernel.org,
	linux-api@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 00/18] kthreads/signal: Safer kthread API and signal
 handling

On Fri, Jun 05, 2015 at 05:00:59PM +0200, Petr Mladek wrote:
> Kthreads are implemented as an infinite loop. They include check points
> for termination, freezer, parking, and even signal handling.
> 
> We need to touch all kthreads every time we want to add or
> modify the behavior of such checkpoints. It is not easy because
> there are several hundreds of kthreads and each of them is
> implemented in a slightly different way.
> 
> This anarchy brings potentially broken or non-standard behavior.
> For example, few kthreads already handle signals a strange way.
> 
> 
> This patchset is a _proof-of-concept_ how to improve the situation.

Maybe it might be a better idea to audit the existing callers of
signals for kthreads and first check if we can get rid of them.  Then
as a second step if any are left convert them to signalfd-style
operation where signals aren't checked synchronously but as something
the threads can consume on a as needed basis.
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