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

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Message-ID: <20200501184935.GD9191@pick.fieldses.org>
Date:   Fri, 1 May 2020 14:49:35 -0400
From:   "J. Bruce Fields" <bfields@...hat.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "open list:NFS, SUNRPC, AND..." <linux-nfs@...r.kernel.org>,
        Jeff Layton <jlayton@...hat.com>,
        David Howells <dhowells@...hat.com>, Shaohua Li <shli@...com>,
        Oleg Nesterov <oleg@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] allow multiple kthreadd's

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.

> Can't that be done with kthread_data()?

Huh, maybe so, thanks.

I need to check this from generic file locking code that could be run by
any task--but I assume there's an easy way I can check if I'm a kthread
before calling  kthread_data(current).

I do expect to expose a delegation interface for userspace servers
eventually too.  But we could do the tgid check for them and still use
kthread_data() for nfsd.  That might work.

--b.