From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6DC38C6FA8E for ; Thu, 2 Mar 2023 13:22:48 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pXitF-0008E9-OW; Thu, 02 Mar 2023 08:22:33 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pXitB-0008DP-R7 for qemu-devel@nongnu.org; Thu, 02 Mar 2023 08:22:31 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pXit7-00039W-Vu for qemu-devel@nongnu.org; Thu, 02 Mar 2023 08:22:28 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1677763344; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=JjVZ+XfdcKtGHX+0QmKEz5Xdu0jH7j+Ilb1KLQrddZ8=; b=EaLJ9HuyAeOnND+Jntj++aCt48ACFBnGqWbG4yGzN9jK8iiJI447VSuDYVa0mQDe/CAQ+u 8aAkeEDRb721HB7lt7x2g16phFo0jMKfavqy46NDBe2TRmXPXa2r09dJ02fPTNPK/5Wy3K jQT0+hh2G1oPrYPeGORXYKhqX3ytHho= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-437-WWc2WY4xMv261yGBpV-UaA-1; Thu, 02 Mar 2023 08:22:08 -0500 X-MC-Unique: WWc2WY4xMv261yGBpV-UaA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D1FBE38123AE; Thu, 2 Mar 2023 13:22:07 +0000 (UTC) Received: from localhost (unknown [10.39.193.244]) by smtp.corp.redhat.com (Postfix) with ESMTP id 432662026D4B; Thu, 2 Mar 2023 13:22:07 +0000 (UTC) Date: Thu, 2 Mar 2023 08:22:05 -0500 From: Stefan Hajnoczi To: Markus Armbruster Cc: qemu-devel@nongnu.org, Fam Zheng , qemu-block@nongnu.org, Emanuele Giuseppe Esposito , Kevin Wolf , "Dr. David Alan Gilbert" , Hanna Reitz Subject: Re: [PATCH 5/6] hmp: convert handle_hmp_command() to AIO_WAIT_WHILE_UNLOCKED() Message-ID: <20230302132205.GB2485531@fedora> References: <20230301205801.2453491-1-stefanha@redhat.com> <20230301205801.2453491-6-stefanha@redhat.com> <87ttz3sju0.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="s16+r/V2ms9fi/iW" Content-Disposition: inline In-Reply-To: <87ttz3sju0.fsf@pond.sub.org> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --s16+r/V2ms9fi/iW Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Mar 02, 2023 at 08:17:43AM +0100, Markus Armbruster wrote: > Stefan Hajnoczi writes: >=20 > > The HMP monitor runs in the main loop thread. Calling >=20 > Correct. >=20 > > AIO_WAIT_WHILE(qemu_get_aio_context(), ...) from the main loop thread is > > equivalent to AIO_WAIT_WHILE_UNLOCKED(NULL, ...) because neither unlocks > > the AioContext and the latter's assertion that we're in the main loop > > succeeds. > > > > Signed-off-by: Stefan Hajnoczi > > --- > > monitor/hmp.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/monitor/hmp.c b/monitor/hmp.c > > index 2aa85d3982..5ecbdac802 100644 > > --- a/monitor/hmp.c > > +++ b/monitor/hmp.c > > @@ -1167,7 +1167,7 @@ void handle_hmp_command(MonitorHMP *mon, const ch= ar *cmdline) > > Coroutine *co =3D qemu_coroutine_create(handle_hmp_command_co,= &data); > > monitor_set_cur(co, &mon->common); > > aio_co_enter(qemu_get_aio_context(), co); > > - AIO_WAIT_WHILE(qemu_get_aio_context(), !data.done); > > + AIO_WAIT_WHILE_UNLOCKED(NULL, !data.done); > > } > > =20 > > qobject_unref(qdict); >=20 > Acked-by: Markus Armbruster >=20 > For an R-by, I need to understand this in more detail. I'm not familiar > with the innards of AIO_WAIT_WHILE() & friends, so I need to go real > slow. >=20 > We change >=20 > ctx from qemu_get_aio_context() to NULL > unlock from true to false >=20 > in >=20 > bool waited_ =3D false; \ > AioWait *wait_ =3D &global_aio_wait; \ > AioContext *ctx_ =3D (ctx); \ > /* Increment wait_->num_waiters before evaluating cond. */ \ > qatomic_inc(&wait_->num_waiters); \ > /* Paired with smp_mb in aio_wait_kick(). */ \ > smp_mb(); \ > if (ctx_ && in_aio_context_home_thread(ctx_)) { \ > while ((cond)) { \ > aio_poll(ctx_, true); \ > waited_ =3D true; \ > } \ > } else { \ > assert(qemu_get_current_aio_context() =3D=3D \ > qemu_get_aio_context()); \ > while ((cond)) { \ > if (unlock && ctx_) { \ > aio_context_release(ctx_); \ > } \ > aio_poll(qemu_get_aio_context(), true); \ > if (unlock && ctx_) { \ > aio_context_acquire(ctx_); \ > } \ > waited_ =3D true; \ > } \ > } \ > qatomic_dec(&wait_->num_waiters); \ > waited_; }) >=20 > qemu_get_aio_context() is non-null here, correct? qemu_get_aio_context() always returns the main loop thread's AioContext. qemu_get_current_aio_context() returns the AioContext that was most recently set in the my_aiocontext thread-local variable for IOThreads, the main loop's AioContext for BQL threads, or NULL for threads that don't use AioContext at all. > What's the value of in_aio_context_home_thread(qemu_get_aio_context())? This function checks whether the given AioContext is associated with this thread. In a BQL thread it returns true if the context is the main loop's AioContext. In an IOThread it returns true if the context is the IOThread's AioContext. Otherwise it returns false. --s16+r/V2ms9fi/iW Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmQAov0ACgkQnKSrs4Gr c8gwDQf9HGcEZ0qisa9Gzp+xSRbI5UcocnkUsTED9FF+rVB4u/NmokXxHOLej0UB DULk9j+aCjKK0vc2zh0XJg4/uzeA1wDqOXdrKjwF4b5cmYH5zS8+odINAdum0yGE JuXgjG3n7SB85aAdDbauJokJEXI6qtvHfOHCAdOamiH4QxUpG5YyEWUY159DHdND oPN8V59DULzpWBfRXq0Ie56tDWrLnqDy9IuHwOU1ZMM/FycDiMeYiwdo7Ss4LCZu MWuseTqyuo3/kzrGUBa0CGlzK1t0ZRxUjnkKFKOPJlN/Q1hUMTX6/y3GLsXCBjt5 7SXV5qLjWSJJEPZWVUUWvMbxrCdYYg== =FQCW -----END PGP SIGNATURE----- --s16+r/V2ms9fi/iW--