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

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Date:   Mon, 4 May 2020 22:15:14 -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. Can't that be done with kthread_data()?

Yeah, so I'd forgotten about kthread->data.

We're currently using it to pass the struct svc_rqst that a new nfsd
thread needs.  But once the new thread has gotten that, I guess it could
set kthread->data to some global value that it uses to say "I'm a knfsd
thread"?

I suppose that would work.

Though now I'm feeling greedy: it would be nice to have both some kind
of global flag, *and* keep kthread->data pointing to svc_rqst (as that
would give me a simpler and quicker way to figure out which client is
conflicting).  Could I take a flag bit in kthread->flags, maybe?

--b.