From patchwork Mon Jun 14 08:29:25 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Emanuele Giuseppe Esposito X-Patchwork-Id: 1491571 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=IMXG3P4f; dkim-atps=neutral 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 ozlabs.org (Postfix) with ESMTPS id 4G3PmW1CWLz9sT6 for ; Mon, 14 Jun 2021 18:31:05 +1000 (AEST) Received: from localhost ([::1]:42566 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lshzp-0002Hh-I5 for incoming@patchwork.ozlabs.org; Mon, 14 Jun 2021 04:31:01 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44090) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lshyX-0002HJ-FM for qemu-devel@nongnu.org; Mon, 14 Jun 2021 04:29:41 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:42985) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lshyU-0005nu-UW for qemu-devel@nongnu.org; Mon, 14 Jun 2021 04:29:40 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623659378; 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=gKdPfoWe4aFt2af46WN/oDroSsaqSGaKcdne26c7v7k=; b=IMXG3P4fA5/4Ak/QR39S6XdvQUKFEIcRsexeJ3aU2UbwogouJRd4DBuQZh+61ymDYZFeYC NhpO/NGi7cXy0FInBNzjZtNZVpfARjI0CaW7V4XpYy45+6fRCrwuGiKLblzYkYF24lomWV KNobMcsETBHC2yBYv5tL/qabVyTxrI0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-465-pYC96hoPNka4vOyMSFQsuw-1; Mon, 14 Jun 2021 04:29:36 -0400 X-MC-Unique: pYC96hoPNka4vOyMSFQsuw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A0E39100CF6A; Mon, 14 Jun 2021 08:29:35 +0000 (UTC) Received: from localhost.localdomain (ovpn-113-49.ams2.redhat.com [10.36.113.49]) by smtp.corp.redhat.com (Postfix) with ESMTP id 74F5A5D9D3; Mon, 14 Jun 2021 08:29:33 +0000 (UTC) From: Emanuele Giuseppe Esposito To: qemu-block@nongnu.org Subject: [PATCH v5 0/6] blkdebug: fix racing condition when iterating on Date: Mon, 14 Jun 2021 10:29:25 +0200 Message-Id: <20210614082931.24925-1-eesposit@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eesposit@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=eesposit@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.199, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Emanuele Giuseppe Esposito , Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, Max Reitz , Paolo Bonzini , Eric Blake Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" When qemu_coroutine_enter is executed in a loop (even QEMU_FOREACH_SAFE), the new routine can modify the list, for example removing an element, causing problem when control is given back to the caller that continues iterating on the same list. Patch 1 solves the issue in blkdebug_debug_resume by restarting the list walk after every coroutine_enter if list has to be fully iterated. Patches 2,3,4 aim to fix blkdebug_debug_event by gathering all actions that the rules make in a counter and invoking the respective coroutine_yeld only after processing all requests. Patch 5-6 are somewhat independent of the others, patch 5 removes the need of new_state field, and patch 6 adds a lock to protect rules and suspended_reqs; right now everything works because it's protected by the AioContext lock. This is a preparation for the current proposal of removing the AioContext lock and instead using smaller granularity locks to allow multiple iothread execution in the same block device. Signed-off-by: Emanuele Giuseppe Esposito --- v5: * Add comment in patch 1 to explain why we don't need _SAFE in for loop * Move the state update (s->state = new_state) in patch 5, to maintain the same existing effect in all patches Emanuele Giuseppe Esposito (6): blkdebug: refactor removal of a suspended request blkdebug: move post-resume handling to resume_req_by_tag blkdebug: track all actions blkdebug: do not suspend in the middle of QLIST_FOREACH_SAFE block/blkdebug: remove new_state field and instead use a local variable blkdebug: protect rules and suspended_reqs with a lock block/blkdebug.c | 136 ++++++++++++++++++++++++++++++++--------------- 1 file changed, 92 insertions(+), 44 deletions(-)