From nobody Mon Feb 9 13:38:39 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=fail; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 16443384710921008.6124912834687; Tue, 8 Feb 2022 08:41:11 -0800 (PST) Received: from localhost ([::1]:39998 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nHTYE-0003LA-KR for importer@patchew.org; Tue, 08 Feb 2022 11:41:10 -0500 Received: from eggs.gnu.org ([209.51.188.92]:55232) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nHRb3-0003K3-BA for qemu-devel@nongnu.org; Tue, 08 Feb 2022 09:36:00 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:40100) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nHRay-0008I6-R4 for qemu-devel@nongnu.org; Tue, 08 Feb 2022 09:35:57 -0500 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-25-nb8ePTt5ONWodZrRohg_6w-1; Tue, 08 Feb 2022 09:35:40 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 76EDD839A55; Tue, 8 Feb 2022 14:35:39 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6CF7F70F55; Tue, 8 Feb 2022 14:35:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1644330944; 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: in-reply-to:in-reply-to:references:references; bh=cAhOZbml3Q1zb4po3mafgs+kV8+i/Xa5f70Ya2Uc1Aw=; b=ayPatg00x0sRO6NE61BryLP9aDXUhC9l3w3xWWx4ExYMOoVQUPqGryOA+eixDnv4UZBExo D/NWo2hkgPrYr3naT97l+rY0pfaZMBXFgtBX22nl0XsJZB3vtIYJWapJ0+N6N03rHVfmz/ lSvvJemFVTnRU0BOknkULkNZxLMBBao= X-MC-Unique: nb8ePTt5ONWodZrRohg_6w-1 From: Emanuele Giuseppe Esposito To: qemu-block@nongnu.org Subject: [PATCH v5 18/20] jobs: protect job.aio_context with BQL and job_mutex Date: Tue, 8 Feb 2022 09:35:11 -0500 Message-Id: <20220208143513.1077229-19-eesposit@redhat.com> In-Reply-To: <20220208143513.1077229-1-eesposit@redhat.com> References: <20220208143513.1077229-1-eesposit@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 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 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+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=eesposit@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable 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: , Cc: Kevin Wolf , Fam Zheng , Vladimir Sementsov-Ogievskiy , Wen Congyang , Xie Changlong , Emanuele Giuseppe Esposito , Markus Armbruster , qemu-devel@nongnu.org, Hanna Reitz , Stefan Hajnoczi , Paolo Bonzini , John Snow Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1644338479337100001 Content-Type: text/plain; charset="utf-8" In order to make it thread safe, implement a "fake rwlock", where we allow reads under BQL *or* job_mutex held, but writes only under BQL *and* job_mutex. The only write we have is in child_job_set_aio_ctx, which always happens under drain (so the job is paused). For this reason, introduce job_set_aio_context and make sure that the context is set under BQL, job_mutex and drain. Also make sure all other places where the aiocontext is read are protected. Suggested-by: Paolo Bonzini Signed-off-by: Emanuele Giuseppe Esposito --- block/replication.c | 2 +- blockjob.c | 3 ++- include/qemu/job.h | 19 ++++++++++++++++++- job.c | 12 ++++++++++++ 4 files changed, 33 insertions(+), 3 deletions(-) diff --git a/block/replication.c b/block/replication.c index 50ea778937..68018948b9 100644 --- a/block/replication.c +++ b/block/replication.c @@ -148,8 +148,8 @@ static void replication_close(BlockDriverState *bs) } if (s->stage =3D=3D BLOCK_REPLICATION_FAILOVER) { commit_job =3D &s->commit_job->job; - assert(commit_job->aio_context =3D=3D qemu_get_current_aio_context= ()); WITH_JOB_LOCK_GUARD() { + assert(commit_job->aio_context =3D=3D qemu_get_current_aio_con= text()); job_cancel_sync_locked(commit_job, false); } } diff --git a/blockjob.c b/blockjob.c index 04d868f020..afb0e9ad5e 100644 --- a/blockjob.c +++ b/blockjob.c @@ -154,12 +154,13 @@ static void child_job_set_aio_ctx(BdrvChild *c, AioCo= ntext *ctx, bdrv_set_aio_context_ignore(sibling->bs, ctx, ignore); } =20 - job->job.aio_context =3D ctx; + job_set_aio_context(&job->job, ctx); } =20 static AioContext *child_job_get_parent_aio_context(BdrvChild *c) { BlockJob *job =3D c->opaque; + assert(qemu_in_main_thread()); =20 return job->job.aio_context; } diff --git a/include/qemu/job.h b/include/qemu/job.h index dfbf2ea501..ca46e46f5b 100644 --- a/include/qemu/job.h +++ b/include/qemu/job.h @@ -75,7 +75,12 @@ typedef struct Job { ProgressMeter progress; =20 =20 - /** AioContext to run the job coroutine in */ + /** + * AioContext to run the job coroutine in. + * This field can be read when holding either the BQL (so we are in + * the main loop) or the job_mutex. + * Instead, it can be only written when we hold *both* BQL and job_mut= ex. + */ AioContext *aio_context; =20 /** Reference count of the block job */ @@ -706,4 +711,16 @@ void job_dismiss_locked(Job **job, Error **errp); int job_finish_sync_locked(Job *job, void (*finish)(Job *, Error **errp), Error **errp); =20 +/** + * Sets the @job->aio_context. + * Called with job_mutex *not* held. + * + * This function must run in the main thread to protect against + * concurrent read in job_finish_sync_locked(), + * takes the job_mutex lock to protect against the read in + * job_do_yield_locked(), and must be called when the coroutine + * is quiescent. + */ +void job_set_aio_context(Job *job, AioContext *ctx); + #endif diff --git a/job.c b/job.c index f05850a337..7a07d25ec3 100644 --- a/job.c +++ b/job.c @@ -354,6 +354,17 @@ Job *job_get_locked(const char *id) return NULL; } =20 +void job_set_aio_context(Job *job, AioContext *ctx) +{ + /* protect against read in job_finish_sync_locked and job_start */ + assert(qemu_in_main_thread()); + /* protect against read in job_do_yield_locked */ + JOB_LOCK_GUARD(); + /* ensure the coroutine is quiescent while the AioContext is changed */ + assert(job->pause_count > 0); + job->aio_context =3D ctx; +} + /* Called with job_mutex *not* held. */ static void job_sleep_timer_cb(void *opaque) { @@ -1256,6 +1267,7 @@ int job_finish_sync_locked(Job *job, void (*finish)(J= ob *, Error **errp), { Error *local_err =3D NULL; int ret; + assert(qemu_in_main_thread()); =20 job_ref_locked(job); =20 --=20 2.31.1