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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Neil Brown <neilb@suse.de>
CC:     Chuck Lever <cel@kernel.org>, Jeff Layton <jlayton@kernel.org>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH 10/14] SUNRPC: change svc_pool_wake_idle_thread() to
 return nothing.
Thread-Topic: [PATCH 10/14] SUNRPC: change svc_pool_wake_idle_thread() to
 return nothing.
Thread-Index: Adm6QrZKr5eZOwInNUOTZRGHjk+s9Q==
Date:   Wed, 19 Jul 2023 13:12:47 +0000
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> On Jul 18, 2023, at 9:16 PM, NeilBrown <neilb@suse.de> wrote:
>=20
> On Tue, 18 Jul 2023, Chuck Lever wrote:
>> On Tue, Jul 18, 2023 at 04:38:08PM +1000, NeilBrown wrote:
>>> No callers of svc_pool_wake_idle_thread() care which thread was woken -
>>> except one that wants to trace the wakeup.  For now we drop that
>>> tracepoint.
>>=20
>> That's an important tracepoint, IMO.
>>=20
>> It might be better to have svc_pool_wake_idle_thread() return void
>> right from it's introduction, and move the tracepoint into that
>> function. I can do that and respin if you agree.
>=20
> Mostly I agree.
>=20
> It isn't clear to me how you would handle trace_svc_xprt_enqueue(),
> as there would be no code that can see both the trigger xprt, and the
> woken rqst.
>=20
> I also wonder if having the trace point when the wake-up is requested
> makes any sense, as there is no guarantee that thread with handle that
> xprt.
>=20
> Maybe the trace point should report when the xprt is dequeued.  i.e.
> maybe trace_svc_pool_awoken() should report the pid, and we could have
> trace_svc_xprt_enqueue() only report the xprt, not the rqst.

I'll come up with something that rearranges the tracepoints so that
svc_pool_wake_idle_thread() can return void.

svc_pool_wake_idle_thread() can save the waker's PID in svc_rqst
somewhere, for example. The dequeue tracepoint can then report that
(if it's still interesting when we're all done with this work).


--
Chuck Lever