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 BE02CC624B4 for ; Thu, 23 Nov 2023 19:50:32 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1r6Fhm-0001zq-9y; Thu, 23 Nov 2023 14:49:42 -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 1r6Fhl-0001xV-4z for qemu-devel@nongnu.org; Thu, 23 Nov 2023 14:49:41 -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 1r6Fhj-0000cz-Lw for qemu-devel@nongnu.org; Thu, 23 Nov 2023 14:49:40 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1700768978; 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: content-transfer-encoding:content-transfer-encoding; bh=vBExvsNxM45JG0GTOZcb0ZCEaSTtqFHbc/mayKRz//o=; b=YONBHL/qZrBED1ydYQ37y+VOeAH0RoOrsP1Z2slxDgRqJltvhiCtdm3vlugcPJ6xOXqkMK +9YH9xP9zj83D/eLDLrpysQF7uLA2F+QliCr19rttLGjHqoUcpGiT8VDie9JFclg9nwZ5M M8WhOE85ZQiOWFcHkrcilaYqaxwv8p4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-73-RTL7GcyoMBGxB_GeT5883w-1; Thu, 23 Nov 2023 14:49:34 -0500 X-MC-Unique: RTL7GcyoMBGxB_GeT5883w-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 823EE828AC2; Thu, 23 Nov 2023 19:49:34 +0000 (UTC) Received: from localhost (unknown [10.39.192.72]) by smtp.corp.redhat.com (Postfix) with ESMTP id A7C9B1121306; Thu, 23 Nov 2023 19:49:33 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: "Michael S. Tsirkin" , David Hildenbrand , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Peter Xu , Paolo Bonzini , Fam Zheng , Stefan Hajnoczi Subject: [PATCH 0/4] scsi: eliminate AioContext lock Date: Thu, 23 Nov 2023 14:49:27 -0500 Message-ID: <20231123194931.171598-1-stefanha@redhat.com> Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.3 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.058, 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_H4=0.001, RCVD_IN_MSPIKE_WL=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 The SCSI subsystem uses the AioContext lock to protect internal state. This is necessary because the main loop and the IOThread can access SCSI state in parallel. This inter-thread access happens during scsi_device_purge_requests() and scsi_dma_restart_cb(). This patch series modifies the code so SCSI state is only accessed from the IOThread that is executing requests. Once this has been achieved the AioContext lock is no longer necessary. Note that a few aio_context_acquire()/aio_context_release() calls still remain after this series. They surround API calls that invoke AIO_WAIT_WHILE() and therefore still rely on the AioContext lock for now. Stefan Hajnoczi (4): scsi: only access SCSIDevice->requests from one thread virtio-scsi: don't lock AioContext around virtio_queue_aio_attach_host_notifier() scsi: don't lock AioContext in I/O code path dma-helpers: don't lock AioContext in dma_blk_cb() include/hw/scsi/scsi.h | 7 +- hw/scsi/scsi-bus.c | 174 ++++++++++++++++++++++---------- hw/scsi/scsi-disk.c | 23 ----- hw/scsi/scsi-generic.c | 20 +--- hw/scsi/virtio-scsi-dataplane.c | 8 +- system/dma-helpers.c | 7 +- 6 files changed, 130 insertions(+), 109 deletions(-) -- 2.42.0