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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 AM5PR0802MB2529.eurprd08.prod.outlook.com (2603:10a6:203:9e::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4108.26; Mon, 10 May 2021 11:40:22 +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 15.20.4108.031; Mon, 10 May 2021 11:40:22 +0000 Subject: Re: [PATCH 5/6] co-shared-resource: protect with a mutex To: Emanuele Giuseppe Esposito , qemu-block@nongnu.org Cc: John Snow , Stefan Hajnoczi , Kevin Wolf , Max Reitz , Paolo Bonzini , qemu-devel@nongnu.org References: <20210510085941.22769-1-eesposit@redhat.com> <20210510085941.22769-6-eesposit@redhat.com> From: Vladimir Sementsov-Ogievskiy Message-ID: <57fd4d5f-4645-905f-998c-a120c042fdc7@virtuozzo.com> Date: Mon, 10 May 2021 14:40:21 +0300 User-Agent: Mozilla/5.0 (X11; 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envelope-from=vsementsov@virtuozzo.com; helo=EUR03-VE1-obe.outbound.protection.outlook.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_NONE=-0.0001, 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" 10.05.2021 11:59, 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. But it doesn't. It's called only from co_get_from_shres(). So, better make it a static function first. > > Signed-off-by: Emanuele Giuseppe Esposito > --- > util/qemu-co-shared-resource.c | 26 ++++++++++++++++++++++---- > 1 file changed, 22 insertions(+), 4 deletions(-) > > diff --git a/util/qemu-co-shared-resource.c b/util/qemu-co-shared-resource.c > index 1c83cd9d29..c455d02a1e 100644 > --- a/util/qemu-co-shared-resource.c > +++ b/util/qemu-co-shared-resource.c > @@ -32,6 +32,7 @@ struct SharedResource { > uint64_t available; > > CoQueue queue; > + QemuMutex lock; > }; > > SharedResource *shres_create(uint64_t total) > @@ -40,17 +41,23 @@ SharedResource *shres_create(uint64_t total) > > s->total = s->available = total; > qemu_co_queue_init(&s->queue); > + qemu_mutex_init(&s->lock); > > return s; > } > > void shres_destroy(SharedResource *s) > { > - assert(s->available == s->total); > + WITH_QEMU_LOCK_GUARD(&s->lock) { > + assert(s->available == s->total); > + } shres_destroy can't be thread-safe anyway, as it does qemu_mutex_destroy() and g_free. So, let's don't try to make part of shres_destroy() "thread safe". > + > + qemu_mutex_destroy(&s->lock); > g_free(s); > } > > -bool co_try_get_from_shres(SharedResource *s, uint64_t n) > +/* Called with lock held */ it should be called _locked() than. > +static bool co_try_get_from_shres_unlocked(SharedResource *s, uint64_t n)> { > if (s->available >= n) { > s->available -= n; > @@ -60,16 +67,27 @@ 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_unlocked(s, n); > + > + return res; > +} > + > void coroutine_fn co_get_from_shres(SharedResource *s, uint64_t n) > { > + QEMU_LOCK_GUARD(&s->lock); > assert(n <= s->total); > - while (!co_try_get_from_shres(s, n)) { > - qemu_co_queue_wait(&s->queue, NULL); > + while (!co_try_get_from_shres_unlocked(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); > -- Best regards, Vladimir