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

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Date:   Tue, 5 May 2020 11:54:05 -0400
From:   Tejun Heo <tj@...nel.org>
To:     "J. Bruce Fields" <bfields@...hat.com>
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

Hello, Bruce.

On Mon, May 04, 2020 at 10:15:14PM -0400, J. Bruce Fields wrote:
> 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?

Hmm... that'd be solvable if kthread->data can point to a struct which does
both things, right? Because it doesn't have free() callback, it's a bit
awkward but the threadfn itself can unlink and RCU-free it before returning.

Thanks.

-- 
tejun