From nobody Mon May 12 01:45:08 2025 Delivered-To: importer2@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer2=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1718727275671653.20984716284; Tue, 18 Jun 2024 09:14:35 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sJbSy-00057m-DQ; Tue, 18 Jun 2024 12:13:52 -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 1sJbSv-00055D-E7 for qemu-devel@nongnu.org; Tue, 18 Jun 2024 12:13:49 -0400 Received: from vps-vb.mhejs.net ([37.28.154.113]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sJbSt-0000uN-Dn for qemu-devel@nongnu.org; Tue, 18 Jun 2024 12:13:49 -0400 Received: from MUA by vps-vb.mhejs.net with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1sJbSc-0001cr-CI; Tue, 18 Jun 2024 18:13:30 +0200 From: "Maciej S. Szmigiero" To: Peter Xu , Fabiano Rosas Cc: Alex Williamson , =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= , Eric Blake , Markus Armbruster , =?UTF-8?q?Daniel=20P=20=2E=20Berrang=C3=A9?= , Avihai Horon , Joao Martins , qemu-devel@nongnu.org Subject: [PATCH v1 08/13] migration/multifd: Convert multifd_send_pages::next_channel to atomic Date: Tue, 18 Jun 2024 18:12:26 +0200 Message-ID: <9ca772abfb2cd8fbd180d981a97d06f57d9fa2d5.1718717584.git.maciej.szmigiero@oracle.com> X-Mailer: git-send-email 2.45.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer2=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=37.28.154.113; envelope-from=mail@maciej.szmigiero.name; helo=vps-vb.mhejs.net X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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+importer2=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer2=patchew.org@nongnu.org X-ZM-MESSAGEID: 1718727277155100008 Content-Type: text/plain; charset="utf-8" From: "Maciej S. Szmigiero" This is necessary for multifd_send_pages() to be able to be called from multiple threads. Signed-off-by: Maciej S. Szmigiero --- migration/multifd.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/migration/multifd.c b/migration/multifd.c index 6e0af84bb9a1..daa34172bf24 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -614,26 +614,38 @@ static bool multifd_send_pages(void) return false; } =20 - /* We wait here, until at least one channel is ready */ - qemu_sem_wait(&multifd_send_state->channels_ready); - /* * next_channel can remain from a previous migration that was * using more channels, so ensure it doesn't overflow if the * limit is lower now. */ - next_channel %=3D migrate_multifd_channels(); - for (i =3D next_channel;; i =3D (i + 1) % migrate_multifd_channels()) { + i =3D qatomic_load_acquire(&next_channel); + if (unlikely(i >=3D migrate_multifd_channels())) { + qatomic_cmpxchg(&next_channel, i, 0); + } + + /* We wait here, until at least one channel is ready */ + qemu_sem_wait(&multifd_send_state->channels_ready); + + while (true) { + int i_next; + if (multifd_send_should_exit()) { return false; } + + i =3D qatomic_load_acquire(&next_channel); + i_next =3D (i + 1) % migrate_multifd_channels(); + if (qatomic_cmpxchg(&next_channel, i, i_next) !=3D i) { + continue; + } + p =3D &multifd_send_state->params[i]; /* * Lockless read to p->pending_job is safe, because only multifd * sender thread can clear it. */ if (qatomic_read(&p->pending_job) =3D=3D false) { - next_channel =3D (i + 1) % migrate_multifd_channels(); break; } }