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bh=kFXWNvX4WWUmsrNJ06vJO56wzR6GldaHLPjmEDLUu3M=; b=Gb9M9DnreumTKQD/2p1Z+iZHhYut9B/ov7+8Bcz4R7HoYQNHHwoXK4XJEkACCwaIcfzY1i H+OKF0CG2sfo9ORq9boQj12ogs67066xpPJKShlQhtPD+4EGm7iNMziGjXGePZ6ZemJDXU tr1WaY60NtC8ISvMuUr4xL/jaiCELy8= X-MC-Unique: phd-a7qkN0SL7MMGoXlN7g-1 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 v9 14/21] jobs: protect job.aio_context with BQL and job_mutex Date: Wed, 6 Jul 2022 16:15:26 -0400 Message-Id: <20220706201533.289775-15-eesposit@redhat.com> In-Reply-To: <20220706201533.289775-1-eesposit@redhat.com> References: <20220706201533.289775-1-eesposit@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 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=170.10.133.124; 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=ham 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+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1657145464095100001 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. 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: Stefan Hajnoczi --- 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 =3D=3D BLOCK_REPLICATION_FAILOVER) { commit_job =3D &s->commit_job->job; - assert(commit_job->aio_context =3D=3D qemu_get_current_aio_context= ()); - job_cancel_sync(commit_job, false); + WITH_JOB_LOCK_GUARD() { + assert(commit_job->aio_context =3D=3D qemu_get_current_aio_con= text()); + job_cancel_sync_locked(commit_job, false); + } } =20 if (s->mode =3D=3D REPLICATION_MODE_SECONDARY) { diff --git a/blockjob.c b/blockjob.c index bce05a9096..0d120ed126 100644 --- a/blockjob.c +++ b/blockjob.c @@ -166,12 +166,13 @@ 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 5709e8d4a8..c144aabefc 100644 --- a/include/qemu/job.h +++ b/include/qemu/job.h @@ -77,7 +77,12 @@ typedef struct Job { =20 /** Protected by AioContext lock */ =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. + * It can be only written when we hold *both* BQL and job_mutex. + */ AioContext *aio_context; =20 /** Reference count of the block job */ @@ -741,4 +746,16 @@ int job_finish_sync(Job *job, void (*finish)(Job *, Er= ror **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 405f39566b..66cae82593 100644 --- a/job.c +++ b/job.c @@ -394,6 +394,17 @@ Job *job_get(const char *id) return job_get_locked(id); } =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) { @@ -1380,6 +1391,7 @@ int job_finish_sync_locked(Job *job, { Error *local_err =3D NULL; int ret; + assert(qemu_in_main_thread()); =20 job_ref_locked(job); =20 --=20 2.31.1