linux-kernel - Re: [PATCH 0/4] allow multiple kthreadd's

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Message-ID: <20200501192219.GG9191@pick.fieldses.org>
Date:   Fri, 1 May 2020 15:22:19 -0400
From:   "J. Bruce Fields" <bfields@...hat.com>
To:     Trond Myklebust <trondmy@...merspace.com>
Cc:     "tj@...nel.org" <tj@...nel.org>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "jlayton@...hat.com" <jlayton@...hat.com>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "shli@...com" <shli@...com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dhowells@...hat.com" <dhowells@...hat.com>,
        "oleg@...hat.com" <oleg@...hat.com>
Subject: Re: [PATCH 0/4] allow multiple kthreadd's

On Fri, May 01, 2020 at 07:05:46PM +0000, Trond Myklebust wrote:
> On Fri, 2020-05-01 at 14:49 -0400, J. Bruce Fields wrote:
> > On Fri, May 01, 2020 at 02:21:54PM -0400, Tejun Heo wrote:
> > > Hello,
> > > 
> > > On Fri, May 01, 2020 at 10:59:24AM -0700, Linus Torvalds wrote:
> > > > Which kind of makes me want to point a finger at Tejun. But it's
> > > > been
> > > > mostly PeterZ touching this file lately..
> > > 
> > > Looks fine to me too. I don't quite understand the usecase tho. It
> > > looks
> > > like all it's being used for is to tag some kthreads as belonging
> > > to the
> > > same group.
> > 
> > Pretty much.
> 
> Wen running an instance of knfsd from inside a container, you want to
> be able to have the knfsd kthreads be parented to the container init
> process so that they get killed off when the container is killed.
> 
> Right now, we can easily leak those kernel threads simply by killing
> the container.

Oh, got it.

Currently knfsd supports nfs service in containers, but it uses a single
set of threads to serve requests from any container.  It should shut the
server threads down when the last container using them goes away.

--b.