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 83EA6C678D4 for ; Thu, 2 Mar 2023 07:19:18 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pXdCh-0005Ep-Kt; Thu, 02 Mar 2023 02:18:15 -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 1pXdCO-00053L-GE for qemu-devel@nongnu.org; Thu, 02 Mar 2023 02:18:00 -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 1pXdCL-00011a-BP for qemu-devel@nongnu.org; Thu, 02 Mar 2023 02:17:56 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1677741472; 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=CeBSzNi0tSQ9vVgQA45hG85q7ywgTYS3299HiH1yW+A=; b=Jkie97GV6598SlQZG/GVa/y3Emd3JGGWsq68S6hsBry7q0EGAejaSkz+Ke1Vyf7q+gCxIz EkH6SWkVAajeUvzV+Qqesw5SKIZmScPXJvO8sSOYhMnr39VFmpOoOBzzjAdN53M7RyXj0T 5S8lgEA8m+y+EWhDe/HZlCb+DucuX+8= 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-529-AvyyjyUYOSapCTtyVoRxwA-1; Thu, 02 Mar 2023 02:17:45 -0500 X-MC-Unique: AvyyjyUYOSapCTtyVoRxwA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 3B6631C08971; Thu, 2 Mar 2023 07:17:45 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.92]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 144CF440DE; Thu, 2 Mar 2023 07:17:45 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id EDFAC21E6A22; Thu, 2 Mar 2023 08:17:43 +0100 (CET) From: Markus Armbruster To: Stefan Hajnoczi 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() References: <20230301205801.2453491-1-stefanha@redhat.com> <20230301205801.2453491-6-stefanha@redhat.com> Date: Thu, 02 Mar 2023 08:17:43 +0100 In-Reply-To: <20230301205801.2453491-6-stefanha@redhat.com> (Stefan Hajnoczi's message of "Wed, 1 Mar 2023 15:58:00 -0500") Message-ID: <87ttz3sju0.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@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=unavailable 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 Stefan Hajnoczi writes: > The HMP monitor runs in the main loop thread. Calling Correct. > 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 char *cmdline) > Coroutine *co = 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); > } > > qobject_unref(qdict); Acked-by: Markus Armbruster 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. We change ctx from qemu_get_aio_context() to NULL unlock from true to false in bool waited_ = false; \ AioWait *wait_ = &global_aio_wait; \ AioContext *ctx_ = (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_ = true; \ } \ } else { \ assert(qemu_get_current_aio_context() == \ 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_ = true; \ } \ } \ qatomic_dec(&wait_->num_waiters); \ waited_; }) qemu_get_aio_context() is non-null here, correct? What's the value of in_aio_context_home_thread(qemu_get_aio_context())?