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dkim=none (message not signed) header.d=none;nongnu.org; dmarc=none action=none header.from=virtuozzo.com; Received: from AM7PR08MB5494.eurprd08.prod.outlook.com (2603:10a6:20b:dc::15) by AM6PR08MB3958.eurprd08.prod.outlook.com (2603:10a6:20b:a6::30) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4129.28; Tue, 18 May 2021 14:50:31 +0000 Received: from AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::b403:c1a9:6bb7:133]) by AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::b403:c1a9:6bb7:133%7]) with mapi id 15.20.4129.031; Tue, 18 May 2021 14:50:31 +0000 Subject: Re: [PATCH v2 5/5] co-shared-resource: protect with a mutex To: Emanuele Giuseppe Esposito , qemu-block@nongnu.org Cc: John Snow , Kevin Wolf , Max Reitz , Paolo Bonzini , Stefan Hajnoczi , qemu-devel@nongnu.org References: <20210518094058.25952-1-eesposit@redhat.com> <20210518094058.25952-6-eesposit@redhat.com> From: Vladimir Sementsov-Ogievskiy Message-ID: <230633b5-72cf-31f2-5c22-564a0f2b5c3f@virtuozzo.com> Date: Tue, 18 May 2021 17:50:28 +0300 User-Agent: Mozilla/5.0 (X11; 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envelope-from=vsementsov@virtuozzo.com; helo=EUR05-VI1-obe.outbound.protection.outlook.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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, MSGID_FROM_MTA_HEADER=0.001, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 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" 18.05.2021 12:40, Emanuele Giuseppe Esposito wrote: > co-shared-resource is currently not thread-safe, as also reported > in co-shared-resource.h. Add a QemuMutex because co_try_get_from_shres > can also be invoked from non-coroutine context. > > Signed-off-by: Emanuele Giuseppe Esposito > --- > include/qemu/co-shared-resource.h | 4 +--- > util/qemu-co-shared-resource.c | 27 ++++++++++++++++++++++----- > 2 files changed, 23 insertions(+), 8 deletions(-) > > diff --git a/include/qemu/co-shared-resource.h b/include/qemu/co-shared-resource.h > index 4e4503004c..78ca5850f8 100644 > --- a/include/qemu/co-shared-resource.h > +++ b/include/qemu/co-shared-resource.h > @@ -26,15 +26,13 @@ > #ifndef QEMU_CO_SHARED_RESOURCE_H > #define QEMU_CO_SHARED_RESOURCE_H > > - > +/* Accesses to co-shared-resource API are thread-safe */ > typedef struct SharedResource SharedResource; > > /* > * Create SharedResource structure > * > * @total: total amount of some resource to be shared between clients > - * > - * Note: this API is not thread-safe. > */ > SharedResource *shres_create(uint64_t total); > > diff --git a/util/qemu-co-shared-resource.c b/util/qemu-co-shared-resource.c > index 1c83cd9d29..bb875a86be 100644 > --- a/util/qemu-co-shared-resource.c > +++ b/util/qemu-co-shared-resource.c > @@ -28,10 +28,13 @@ > #include "qemu/co-shared-resource.h" > > struct SharedResource { > - uint64_t total; > - uint64_t available; > + uint64_t total; /* Set in shres_create() and not changed anymore */ > > + /* State fields protected by lock */ > + uint64_t available; > CoQueue queue; > + > + QemuMutex lock; > }; > > SharedResource *shres_create(uint64_t total) > @@ -40,6 +43,7 @@ SharedResource *shres_create(uint64_t total) > > s->total = s->available = total; > qemu_co_queue_init(&s->queue); > + qemu_mutex_init(&s->lock); > > return s; > } > @@ -47,10 +51,12 @@ SharedResource *shres_create(uint64_t total) > void shres_destroy(SharedResource *s) > { > assert(s->available == s->total); > + qemu_mutex_destroy(&s->lock); > g_free(s); > } > > -bool co_try_get_from_shres(SharedResource *s, uint64_t n) > +/* Called with lock held. */ > +static bool co_try_get_from_shres_locked(SharedResource *s, uint64_t n) > { > if (s->available >= n) { > s->available -= n; > @@ -60,16 +66,27 @@ bool co_try_get_from_shres(SharedResource *s, uint64_t n) > return false; > } > > +bool co_try_get_from_shres(SharedResource *s, uint64_t n) > +{ > + bool res; > + QEMU_LOCK_GUARD(&s->lock); > + res = co_try_get_from_shres_locked(s, n); > + > + return res; > +} it can be two lines: QEMU_LOCK_GUARD(&s->lock); return co_try_get_from_shres_locked(s, n); > + > void coroutine_fn co_get_from_shres(SharedResource *s, uint64_t n) > { > assert(n <= s->total); > - while (!co_try_get_from_shres(s, n)) { > - qemu_co_queue_wait(&s->queue, NULL); > + QEMU_LOCK_GUARD(&s->lock); > + while (!co_try_get_from_shres_locked(s, n)) { > + qemu_co_queue_wait(&s->queue, &s->lock); > } > } > > void coroutine_fn co_put_to_shres(SharedResource *s, uint64_t n) > { > + QEMU_LOCK_GUARD(&s->lock); > assert(s->total - s->available >= n); > s->available += n; > qemu_co_queue_restart_all(&s->queue); > Reviewed-by: Vladimir Sementsov-Ogievskiy -- Best regards, Vladimir