From patchwork Mon Sep 26 09:32:06 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: 12988488 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 B9F5FC32771 for ; Mon, 26 Sep 2022 09:46:43 +0000 (UTC) Received: from localhost ([::1]:35878 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ockhG-00021y-P8 for qemu-devel@archiver.kernel.org; Mon, 26 Sep 2022 05:46:42 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:54458) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ockTe-0004qB-7H for qemu-devel@nongnu.org; Mon, 26 Sep 2022 05:32:38 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:41598) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ockTT-0000IL-3t for qemu-devel@nongnu.org; Mon, 26 Sep 2022 05:32:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1664184746; 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=dvkZda/QpYGiRqtN92gJDinhJYnAWswbbJmtEOqWTK8=; b=c3Y76bvbzu6KBTQaoLz6WaS5KVOPfn6lCdHgVPU7ClHa9XpLEaR3fO4YmhzGwm/DGx+5tI muG2f/QIpYicdTywA+WussUY5sZml3TTyYpE4UlMcUcZTniCmEPOwTSW4NmRaf4kM4Kr0h tOebqLQo1ycrkN///xUvGlyPzXDzPfc= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-675-ksPq-ycFOm6F-K9YuhTQMw-1; Mon, 26 Sep 2022 05:32:23 -0400 X-MC-Unique: ksPq-ycFOm6F-K9YuhTQMw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C2C3F29ABA08; Mon, 26 Sep 2022 09:32:22 +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 716124B3FC6; Mon, 26 Sep 2022 09:32:22 +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 v12 13/21] jobs: protect job.aio_context with BQL and job_mutex Date: Mon, 26 Sep 2022 05:32:06 -0400 Message-Id: <20220926093214.506243-14-eesposit@redhat.com> In-Reply-To: <20220926093214.506243-1-eesposit@redhat.com> References: <20220926093214.506243-1-eesposit@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 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: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 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_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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. The reads in commit.c and mirror.c are actually safe, because always done under BQL. Note: at this stage, job_{lock/unlock} and job lock guard macros are *nop*. Suggested-by: Paolo Bonzini Signed-off-by: Emanuele Giuseppe Esposito Reviewed-by: Vladimir Sementsov-Ogievskiy --- block/replication.c | 1 + blockjob.c | 3 ++- include/qemu/job.h | 23 ++++++++++++++++++++--- job.c | 12 ++++++++++++ 4 files changed, 35 insertions(+), 4 deletions(-) diff --git a/block/replication.c b/block/replication.c index 55c8f894aa..5977f7a833 100644 --- a/block/replication.c +++ b/block/replication.c @@ -142,6 +142,7 @@ static void replication_close(BlockDriverState *bs) { BDRVReplicationState *s = bs->opaque; Job *commit_job; + GLOBAL_STATE_CODE(); if (s->stage == BLOCK_REPLICATION_RUNNING) { replication_stop(s->rs, false, NULL); diff --git a/blockjob.c b/blockjob.c index 96fb9d9f73..c8919cef9b 100644 --- a/blockjob.c +++ b/blockjob.c @@ -162,12 +162,13 @@ 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; + GLOBAL_STATE_CODE(); return job->job.aio_context; } diff --git a/include/qemu/job.h b/include/qemu/job.h index 5709e8d4a8..50a4c06b93 100644 --- a/include/qemu/job.h +++ b/include/qemu/job.h @@ -74,11 +74,17 @@ typedef struct Job { /* ProgressMeter API is thread-safe */ ProgressMeter progress; + /** + * AioContext to run the job coroutine in. + * The job Aiocontext can be read when holding *either* + * the BQL (so we are in the main loop) or the job_mutex. + * It can only be written when we hold *both* BQL + * and the job_mutex. + */ + AioContext *aio_context; - /** Protected by AioContext lock */ - /** AioContext to run the job coroutine in */ - AioContext *aio_context; + /** Protected by AioContext lock */ /** Reference count of the block job */ int refcnt; @@ -741,4 +747,15 @@ 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 job is quiescent. + */ +void job_set_aio_context(Job *job, AioContext *ctx); + #endif diff --git a/job.c b/job.c index 85ae843f03..c4ac363f08 100644 --- a/job.c +++ b/job.c @@ -396,6 +396,17 @@ 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 */ + GLOBAL_STATE_CODE(); + /* protect against read in job_do_yield_locked */ + JOB_LOCK_GUARD(); + /* ensure the job is quiescent while the AioContext is changed */ + assert(job->paused || job_is_completed_locked(job)); + 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; + GLOBAL_STATE_CODE(); job_ref_locked(job);