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[82.30.61.225]) by smtp.gmail.com with ESMTPSA id m12-20020a7bce0c000000b0037bed2a6fbfsm8024308wmc.37.2022.02.21.08.00.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Feb 2022 08:00:54 -0800 (PST) Date: Mon, 21 Feb 2022 16:00:52 +0000 From: "Dr. David Alan Gilbert" To: Peter Xu Subject: Re: [PATCH 06/20] migration: Add postcopy_thread_create() Message-ID: References: <20220216062809.57179-1-peterx@redhat.com> <20220216062809.57179-7-peterx@redhat.com> MIME-Version: 1.0 In-Reply-To: <20220216062809.57179-7-peterx@redhat.com> User-Agent: Mutt/2.1.5 (2021-12-30) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.129.124; envelope-from=dgilbert@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, 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: , Cc: Leonardo Bras Soares Passos , qemu-devel@nongnu.org, Juan Quintela Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Peter Xu (peterx@redhat.com) wrote: > Postcopy create threads. A common manner is we init a sem and use it to sync > with the thread. Namely, we have fault_thread_sem and listen_thread_sem and > they're only used for this. > > Make it a shared infrastructure so it's easier to create yet another thread. > > Signed-off-by: Peter Xu Reviewed-by: Dr. David Alan Gilbert > --- > migration/migration.h | 8 +++++--- > migration/postcopy-ram.c | 23 +++++++++++++++++------ > migration/postcopy-ram.h | 4 ++++ > migration/savevm.c | 12 +++--------- > 4 files changed, 29 insertions(+), 18 deletions(-) > > diff --git a/migration/migration.h b/migration/migration.h > index 42c7395094..8445e1d14a 100644 > --- a/migration/migration.h > +++ b/migration/migration.h > @@ -70,7 +70,11 @@ struct MigrationIncomingState { > /* A hook to allow cleanup at the end of incoming migration */ > void *transport_data; > void (*transport_cleanup)(void *data); > - > + /* > + * Used to sync thread creations. Note that we can't create threads in > + * parallel with this sem. > + */ > + QemuSemaphore thread_sync_sem; > /* > * Free at the start of the main state load, set as the main thread finishes > * loading state. > @@ -83,13 +87,11 @@ struct MigrationIncomingState { > size_t largest_page_size; > bool have_fault_thread; > QemuThread fault_thread; > - QemuSemaphore fault_thread_sem; > /* Set this when we want the fault thread to quit */ > bool fault_thread_quit; > > bool have_listen_thread; > QemuThread listen_thread; > - QemuSemaphore listen_thread_sem; > > /* For the kernel to send us notifications */ > int userfault_fd; > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c > index 315f784965..d3ec22e6de 100644 > --- a/migration/postcopy-ram.c > +++ b/migration/postcopy-ram.c > @@ -77,6 +77,20 @@ int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp) > &pnd); > } > > +/* > + * NOTE: this routine is not thread safe, we can't call it concurrently. But it > + * should be good enough for migration's purposes. > + */ > +void postcopy_thread_create(MigrationIncomingState *mis, > + QemuThread *thread, const char *name, > + void *(*fn)(void *), int joinable) > +{ > + qemu_sem_init(&mis->thread_sync_sem, 0); > + qemu_thread_create(thread, name, fn, mis, joinable); > + qemu_sem_wait(&mis->thread_sync_sem); > + qemu_sem_destroy(&mis->thread_sync_sem); > +} > + > /* Postcopy needs to detect accesses to pages that haven't yet been copied > * across, and efficiently map new pages in, the techniques for doing this > * are target OS specific. > @@ -901,7 +915,7 @@ static void *postcopy_ram_fault_thread(void *opaque) > trace_postcopy_ram_fault_thread_entry(); > rcu_register_thread(); > mis->last_rb = NULL; /* last RAMBlock we sent part of */ > - qemu_sem_post(&mis->fault_thread_sem); > + qemu_sem_post(&mis->thread_sync_sem); > > struct pollfd *pfd; > size_t pfd_len = 2 + mis->postcopy_remote_fds->len; > @@ -1172,11 +1186,8 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis) > return -1; > } > > - qemu_sem_init(&mis->fault_thread_sem, 0); > - qemu_thread_create(&mis->fault_thread, "postcopy/fault", > - postcopy_ram_fault_thread, mis, QEMU_THREAD_JOINABLE); > - qemu_sem_wait(&mis->fault_thread_sem); > - qemu_sem_destroy(&mis->fault_thread_sem); > + postcopy_thread_create(mis, &mis->fault_thread, "postcopy/fault", > + postcopy_ram_fault_thread, QEMU_THREAD_JOINABLE); > mis->have_fault_thread = true; > > /* Mark so that we get notified of accesses to unwritten areas */ > diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h > index 6d2b3cf124..07684c0e1d 100644 > --- a/migration/postcopy-ram.h > +++ b/migration/postcopy-ram.h > @@ -135,6 +135,10 @@ void postcopy_remove_notifier(NotifierWithReturn *n); > /* Call the notifier list set by postcopy_add_start_notifier */ > int postcopy_notify(enum PostcopyNotifyReason reason, Error **errp); > > +void postcopy_thread_create(MigrationIncomingState *mis, > + QemuThread *thread, const char *name, > + void *(*fn)(void *), int joinable); > + > struct PostCopyFD; > > /* ufd is a pointer to the struct uffd_msg *TODO: more Portable! */ > diff --git a/migration/savevm.c b/migration/savevm.c > index 0ccd7e5e3f..967ff80547 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -1863,7 +1863,7 @@ static void *postcopy_ram_listen_thread(void *opaque) > > migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE, > MIGRATION_STATUS_POSTCOPY_ACTIVE); > - qemu_sem_post(&mis->listen_thread_sem); > + qemu_sem_post(&mis->thread_sync_sem); > trace_postcopy_ram_listen_thread_start(); > > rcu_register_thread(); > @@ -1988,14 +1988,8 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis) > } > > mis->have_listen_thread = true; > - /* Start up the listening thread and wait for it to signal ready */ > - qemu_sem_init(&mis->listen_thread_sem, 0); > - qemu_thread_create(&mis->listen_thread, "postcopy/listen", > - postcopy_ram_listen_thread, NULL, > - QEMU_THREAD_DETACHED); > - qemu_sem_wait(&mis->listen_thread_sem); > - qemu_sem_destroy(&mis->listen_thread_sem); > - > + postcopy_thread_create(mis, &mis->listen_thread, "postcopy/listen", > + postcopy_ram_listen_thread, QEMU_THREAD_DETACHED); > trace_loadvm_postcopy_handle_listen("return"); > > return 0; > -- > 2.32.0 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK