From patchwork Mon Mar 14 13:37:05 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Emanuele Giuseppe Esposito X-Patchwork-Id: 12780166 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 68293C433EF for ; Mon, 14 Mar 2022 13:52:07 +0000 (UTC) Received: from localhost ([::1]:37922 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nTl7G-0001eM-Fz for qemu-devel@archiver.kernel.org; Mon, 14 Mar 2022 09:52:06 -0400 Received: from eggs.gnu.org ([209.51.188.92]:43150) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nTktC-0006zb-AF for qemu-devel@nongnu.org; Mon, 14 Mar 2022 09:37:34 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:60043) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nTkt1-0001dt-FM for qemu-devel@nongnu.org; Mon, 14 Mar 2022 09:37:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1647265042; 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=aXjCuW4SV79Oe6hDfMZZg9exqw8x0C5zPZhM8jzGmMk=; b=cG/3sifn3eRV3CQgGIU5oqw4Z95OHioD6du2EdHCtYV6pZFCl5bLYpOvxeR5BuudzsxWN0 5mnNQ5eZsvSm3YsSrIpjIarU51UGe05QBskvgWYs6gs7wrp9A/tmqFpVdOPdH6zFXQzIt4 cz9wN/t2soxhOF7b8so5cMXNzaWg2Vc= 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-564-IugojKFkMruFNmv406IDiA-1; Mon, 14 Mar 2022 09:37:19 -0400 X-MC-Unique: IugojKFkMruFNmv406IDiA-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id EDF3F899ED2; Mon, 14 Mar 2022 13:37:18 +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 9D10D46503C; Mon, 14 Mar 2022 13:37:18 +0000 (UTC) From: Emanuele Giuseppe Esposito To: qemu-block@nongnu.org Subject: [PATCH v6 16/18] jobs: protect job.aio_context with BQL and job_mutex Date: Mon, 14 Mar 2022 09:37:05 -0400 Message-Id: <20220314133707.2206082-17-eesposit@redhat.com> In-Reply-To: <20220314133707.2206082-1-eesposit@redhat.com> References: <20220314133707.2206082-1-eesposit@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.85 on 10.11.54.10 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=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, RCVD_IN_MSPIKE_H5=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=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+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 | 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 == BLOCK_REPLICATION_FAILOVER) { commit_job = &s->commit_job->job; - assert(commit_job->aio_context == qemu_get_current_aio_context()); WITH_JOB_LOCK_GUARD() { + assert(commit_job->aio_context == qemu_get_current_aio_context()); job_cancel_sync_locked(commit_job, false); } } diff --git a/blockjob.c b/blockjob.c index 2c075db45b..8b9e10813d 100644 --- a/blockjob.c +++ b/blockjob.c @@ -154,12 +154,13 @@ 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 dfbf2ea501..fad4ee8cb3 100644 --- a/include/qemu/job.h +++ b/include/qemu/job.h @@ -75,7 +75,12 @@ typedef struct Job { ProgressMeter progress; - /** 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 */ @@ -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); +/** + * 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 10a5981748..80a0fb34b1 100644 --- a/job.c +++ b/job.c @@ -368,6 +368,17 @@ Job *job_get_locked(const char *id) return NULL; } +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) { @@ -1261,6 +1272,7 @@ int job_finish_sync_locked(Job *job, void (*finish)(Job *, Error **errp), { Error *local_err = NULL; int ret; + assert(qemu_in_main_thread()); job_ref_locked(job);