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 078E8C87FCB for ; Fri, 8 Aug 2025 17:06:16 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ukQXP-00030c-JA; Fri, 08 Aug 2025 13:05:52 -0400 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 1ukQXN-0002yt-9y for qemu-devel@nongnu.org; Fri, 08 Aug 2025 13:05:49 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ukQXK-0001Kt-AC for qemu-devel@nongnu.org; Fri, 08 Aug 2025 13:05:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754672744; 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=vQt+CNI6Lv7EOnlvVxpwbQ+XsxjORiU+LOFIMzTVBhU=; b=LLe3I3xmbNInPy5hTcLVFc9x28GR7GeOdnMwMxUBSuKqan3rs3FGlHlmJxRsCFIO+EmrWS vAutNj4ZQcX/rwMSpcfPAc+/IlkEAbYT3N6QC40WROeaETHZSaZnHtFoC2VB6F2Dp6hE3E q/4Ji9ZEmXwVwwKn3ihyazWmfJrO9Ec= Received: from mail-yw1-f200.google.com (mail-yw1-f200.google.com [209.85.128.200]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-394-DKNE8aMSNJaSpw53073BfA-1; Fri, 08 Aug 2025 13:05:43 -0400 X-MC-Unique: DKNE8aMSNJaSpw53073BfA-1 X-Mimecast-MFC-AGG-ID: DKNE8aMSNJaSpw53073BfA_1754672743 Received: by mail-yw1-f200.google.com with SMTP id 00721157ae682-70e73d3c474so36688337b3.3 for ; Fri, 08 Aug 2025 10:05:43 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1754672743; x=1755277543; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=vQt+CNI6Lv7EOnlvVxpwbQ+XsxjORiU+LOFIMzTVBhU=; b=GYe5bpPrjk5dn9csvKUyqk29dnVTlYCgfxwOlzsANwa/UNcQrGH7kTs8T0ABno/VUb vYQOoT2kilZJpwIDFd89Q6uTgC2CygjwSfTLGIw/z1CZI7LGf9eHrqlM9FkBPP/o2boU MxN40NRttP2iezaGZO/vtGtQl//JgG7ovzAjMKmKBZxDihZPPzMNZLsdx5rmgI7klDWM rizA8bZZTmsO8oJXnNlg26YsSQP93z30aCA70kTnCqc8PCAelrmbC8z7WFxzamSaUuaX j/tIa691VNhhteFSwrblERm/9SP+b617zUnylQmYx4ejbEb2pB/qFnweVOct3DYmdAfX 3kOw== X-Gm-Message-State: AOJu0Yw7KKH09DkPI7Cag+Lf1rQohxQ8rLc2icy5In/1UIVgw5hmY/xL T6FKbUTLif++NVQywkdCyS+tz0EF5tKGCRqiSQa7SC7f5gtpKGygjbLvq+bh93Rz/CsLIHcY3lp 2vU3f2zppL3Z1nY1ZhEttFYxCYDpV1HtkT33vWGi6U/71AMN1swHn8ZIo X-Gm-Gg: ASbGncu7oZ1L3THIWV/agTztrxED42HIfJMNOnYNidUuzAbktHb8K7E6cNA7N2+MHcR fIgYNlLAR+NHRtoHvutAOyZYdst9iqpfUhX5a1V0ce4rGwU+HiWUNLHdJICnSHuG9iHkH4tbvjp P4l3KxecTbv2Dwb39HA8GOPlQSmFCF8k6qxCmGZbValE4xd17hW5CJSZEv8WRw0qaBljybrLnWb g8AE4p6+bGRxivMup2rnqlOxlPiNmxkaGOnOQXE/AdQ7221/gAPoIGhhaaq+oo7fTwl+64H85Rk JzRjkn+XmMsv5uEl1G+fLJBE+Sgf69YB X-Received: by 2002:a05:690c:6d13:b0:71a:18fb:6eaa with SMTP id 00721157ae682-71bf0cedbc2mr44917327b3.3.1754672742483; Fri, 08 Aug 2025 10:05:42 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEUhyDVu0cLQUuQ43PjXootakVZJ03zT+ulg+S4/cBvNhXSnN1aYagRkumlCxEjnB70tiUoBQ== X-Received: by 2002:a05:690c:6d13:b0:71a:18fb:6eaa with SMTP id 00721157ae682-71bf0cedbc2mr44916747b3.3.1754672742019; Fri, 08 Aug 2025 10:05:42 -0700 (PDT) Received: from x1.local ([174.89.135.171]) by smtp.gmail.com with ESMTPSA id 00721157ae682-71b5a5cc216sm53278607b3.73.2025.08.08.10.05.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 Aug 2025 10:05:41 -0700 (PDT) Date: Fri, 8 Aug 2025 13:05:28 -0400 From: Peter Xu To: Juraj Marcin Cc: qemu-devel@nongnu.org, Jiri Denemark , Stefan Weil , Paolo Bonzini , Fabiano Rosas Subject: Re: [RFC PATCH 3/4] migration: Make listen thread joinable Message-ID: References: <20250807114922.1013286-1-jmarcin@redhat.com> <20250807114922.1013286-4-jmarcin@redhat.com> <2svq64am2z4dr7q7x2jozlgzhiwluzi3je3f4acjylxqyzbxml@mnqscmlofjro> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <2svq64am2z4dr7q7x2jozlgzhiwluzi3je3f4acjylxqyzbxml@mnqscmlofjro> Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-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 On Fri, Aug 08, 2025 at 01:08:39PM +0200, Juraj Marcin wrote: > Hi Peter, > > On 2025-08-07 16:57, Peter Xu wrote: > > On Thu, Aug 07, 2025 at 01:49:11PM +0200, Juraj Marcin wrote: > > > From: Juraj Marcin > > > > > > This patch allows joining the migration listen thread. This is done in > > > preparation for the introduction of "postcopy-setup" state at the > > > beginning of a postcopy migration, when destination can fail gracefully > > > and source side then resume to a running state. > > > > > > In case of such failure, to gracefully perform all cleanup in the main > > > migration thread, we need to wait for the listen thread to exit, which > > > can be done by joining it. > > > > > > Signed-off-by: Juraj Marcin > > > --- > > > migration/migration.c | 1 + > > > migration/savevm.c | 2 +- > > > 2 files changed, 2 insertions(+), 1 deletion(-) > > > > > > diff --git a/migration/migration.c b/migration/migration.c > > > index e5ce2940d5..8174e811eb 100644 > > > --- a/migration/migration.c > > > +++ b/migration/migration.c > > > @@ -901,6 +901,7 @@ process_incoming_migration_co(void *opaque) > > > * Postcopy was started, cleanup should happen at the end of the > > > * postcopy thread. > > > */ > > > + qemu_thread_detach(&mis->listen_thread); > > > trace_process_incoming_migration_co_postcopy_end_main(); > > > goto out; > > > } > > > diff --git a/migration/savevm.c b/migration/savevm.c > > > index fabbeb296a..d2360be53c 100644 > > > --- a/migration/savevm.c > > > +++ b/migration/savevm.c > > > @@ -2217,7 +2217,7 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis) > > > mis->have_listen_thread = true; > > > postcopy_thread_create(mis, &mis->listen_thread, > > > MIGRATION_THREAD_DST_LISTEN, > > > - postcopy_ram_listen_thread, QEMU_THREAD_DETACHED); > > > + postcopy_ram_listen_thread, QEMU_THREAD_JOINABLE); > > > > This is good; I actually forgot it used to be detached.. > > > > Instead of proactively detach it above, could we always properly join it > > However, after the main thread finishes loading device state from the > package, process_incoming_migration_co() exits, and IIUC main thread is > then no longer occupied with migration. So, if we should instead join > the listen thread, we probably should yield the coroutine until the > listen thread can be joined, so we are not blocking the main thread? Or could we schedule a bottom half at the end of postcopy_ram_listen_thread() to join itself? We could move something over into the BH: ... join() ... mis->have_listen_thread = false; migration_incoming_state_destroy(); object_unref(OBJECT(migr)); > > > (and hopefully every migration thread)? Then we could drop patch 1 too. > > If I haven't missed any, there are no detached migration threads except > listen and get dirty rate threads. Yep. >From mgmt pov, IMHO it's always good we create joinable threads. But we can leave the calc_dirty_rate thread until necessary. -- Peter Xu