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 3056CC43334 for ; Wed, 29 Jun 2022 14:35:47 +0000 (UTC) Received: from localhost ([::1]:57212 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1o6YnC-0006fX-9Y for qemu-devel@archiver.kernel.org; Wed, 29 Jun 2022 10:35:46 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:36756) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o6YU9-00083a-VQ for qemu-devel@nongnu.org; Wed, 29 Jun 2022 10:16:06 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:40339) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o6YTy-00026X-6A for qemu-devel@nongnu.org; Wed, 29 Jun 2022 10:16:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1656512153; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8oGklbGMcXuEKkCX2fd3FQ7B2T97dW+S6k0jrBlY1FI=; b=NUQGIlT8NOgz5jdK0XrNS2tBbE5E7jCtSMh4952lx4A7Y8rJIKE5Y+dzsx2M3bAfxl6Bp4 aloxLhUwrNI/pTkXECdAd6B+aiAwsxcYpvnHWls/65V9QrCwA7NzOhivoHP7P82I53ueSY fYVsggPrQa+EPfjQdeMA/vr2MGSXl94= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-612-xm2NyXVnPJq7wUCnWoPYtg-1; Wed, 29 Jun 2022 10:15:49 -0400 X-MC-Unique: xm2NyXVnPJq7wUCnWoPYtg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BEE2A936EB1; Wed, 29 Jun 2022 14:15:48 +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 6F23C9D63; Wed, 29 Jun 2022 14:15:48 +0000 (UTC) From: Emanuele Giuseppe Esposito To: qemu-block@nongnu.org Cc: Kevin Wolf , Hanna Reitz , Paolo Bonzini , John Snow , Vladimir Sementsov-Ogievskiy , Wen Congyang , Xie Changlong , Markus Armbruster , Stefan Hajnoczi , Fam Zheng , qemu-devel@nongnu.org, Emanuele Giuseppe Esposito Subject: [PATCH v8 16/20] jobs: protect job.aio_context with BQL and job_mutex Date: Wed, 29 Jun 2022 10:15:34 -0400 Message-Id: <20220629141538.3400679-17-eesposit@redhat.com> In-Reply-To: <20220629141538.3400679-1-eesposit@redhat.com> References: <20220629141538.3400679-1-eesposit@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eesposit@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=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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. Note: at this stage, job_{lock/unlock} and job lock guard macros are *nop*. Suggested-by: Paolo Bonzini Signed-off-by: Emanuele Giuseppe Esposito --- block/replication.c | 6 ++++-- blockjob.c | 3 ++- include/qemu/job.h | 19 ++++++++++++++++++- job.c | 12 ++++++++++++ 4 files changed, 36 insertions(+), 4 deletions(-) diff --git a/block/replication.c b/block/replication.c index 55c8f894aa..2189863df1 100644 --- a/block/replication.c +++ b/block/replication.c @@ -148,8 +148,10 @@ static void replication_close(BlockDriverState *bs) } if (s->stage == BLOCK_REPLICATION_FAILOVER) { commit_job = &s->commit_job->job; - assert(commit_job->aio_context == qemu_get_current_aio_context()); - job_cancel_sync(commit_job, false); + WITH_JOB_LOCK_GUARD() { + assert(commit_job->aio_context == qemu_get_current_aio_context()); + job_cancel_sync_locked(commit_job, false); + } } if (s->mode == REPLICATION_MODE_SECONDARY) { diff --git a/blockjob.c b/blockjob.c index 1075def475..2293a00b4a 100644 --- a/blockjob.c +++ b/blockjob.c @@ -166,12 +166,13 @@ static void child_job_set_aio_ctx(BdrvChild *c, AioContext *ctx, bdrv_set_aio_context_ignore(sibling->bs, ctx, ignore); } - job->job.aio_context = ctx; + job_set_aio_context(&job->job, ctx); } static AioContext *child_job_get_parent_aio_context(BdrvChild *c) { BlockJob *job = c->opaque; + assert(qemu_in_main_thread()); return job->job.aio_context; } diff --git a/include/qemu/job.h b/include/qemu/job.h index e887f88cb2..8f13c3de61 100644 --- a/include/qemu/job.h +++ b/include/qemu/job.h @@ -77,7 +77,12 @@ typedef struct Job { /** Protected by AioContext lock */ - /** 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. + * It can be only written when we hold *both* BQL and job_mutex. + */ AioContext *aio_context; /** Reference count of the block job */ @@ -728,4 +733,16 @@ int job_finish_sync(Job *job, void (*finish)(Job *, Error **errp), int job_finish_sync_locked(Job *job, void (*finish)(Job *, Error **errp), Error **errp); +/** + * 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 8db80b8086..ad2badd107 100644 --- a/job.c +++ b/job.c @@ -394,6 +394,17 @@ Job *job_get(const char *id) return job_get_locked(id); } +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 = ctx; +} + /* Called with job_mutex *not* held. */ static void job_sleep_timer_cb(void *opaque) { @@ -1379,6 +1390,7 @@ int job_finish_sync_locked(Job *job, { Error *local_err = NULL; int ret; + assert(qemu_in_main_thread()); job_ref_locked(job); -- 2.31.1