From patchwork Tue Aug 27 17:54:29 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Maciej S. Szmigiero" X-Patchwork-Id: 13779931 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 787B6C5472F for ; Tue, 27 Aug 2024 17:56:42 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sj0QK-0006h9-CJ; Tue, 27 Aug 2024 13:56:09 -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 1sj0QD-0006Nv-GC for qemu-devel@nongnu.org; Tue, 27 Aug 2024 13:56:02 -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 1sj0QB-0001cG-Tc for qemu-devel@nongnu.org; Tue, 27 Aug 2024 13:56:01 -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 1sj0Px-0002O7-TR; Tue, 27 Aug 2024 19:55:45 +0200 From: "Maciej S. Szmigiero" To: Peter Xu , Fabiano Rosas Cc: Alex Williamson , =?utf-8?q?C=C3=A9dric_Le_G?= =?utf-8?q?oater?= , Eric Blake , Markus Armbruster , =?utf-8?q?Daniel_P_=2E_Berrang=C3=A9?= , Avihai Horon , Joao Martins , qemu-devel@nongnu.org Subject: [PATCH v2 10/17] migration/multifd: Convert multifd_send()::next_channel to atomic Date: Tue, 27 Aug 2024 19:54:29 +0200 Message-ID: <76dc3ad69fa457fd1e358ad3de874474f9f64716.1724701542.git.maciej.szmigiero@oracle.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: References: MIME-Version: 1.0 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, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: "Maciej S. Szmigiero" This is necessary for multifd_send() 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 d5a8e5a9c9b5..b25789dde0b3 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -343,26 +343,38 @@ bool multifd_send(MultiFDSendData **send_data) return false; } - /* 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 %= migrate_multifd_channels(); - for (i = next_channel;; i = (i + 1) % migrate_multifd_channels()) { + i = qatomic_load_acquire(&next_channel); + if (unlikely(i >= 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 = qatomic_load_acquire(&next_channel); + i_next = (i + 1) % migrate_multifd_channels(); + if (qatomic_cmpxchg(&next_channel, i, i_next) != i) { + continue; + } + p = &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) == false) { - next_channel = (i + 1) % migrate_multifd_channels(); break; } }