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[99.254.114.190]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c00a90ce2esm658244285a.103.2025.02.04.09.54.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Feb 2025 09:54:09 -0800 (PST) Date: Tue, 4 Feb 2025 12:54:07 -0500 From: Peter Xu To: "Maciej S. Szmigiero" Cc: Fabiano Rosas , Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Eric Blake , Markus Armbruster , Daniel P =?utf-8?B?LiBCZXJyYW5nw6k=?= , Avihai Horon , Joao Martins , qemu-devel@nongnu.org Subject: Re: [PATCH v4 19/33] migration: Add save_live_complete_precopy_thread handler Message-ID: References: <7561a5d67e113e166c7d43246d52feec6ca06fb5.1738171076.git.maciej.szmigiero@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <7561a5d67e113e166c7d43246d52feec6ca06fb5.1738171076.git.maciej.szmigiero@oracle.com> Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.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, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=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: 2.1.29 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-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Jan 30, 2025 at 11:08:40AM +0100, Maciej S. Szmigiero wrote: > +static int multifd_device_state_save_thread(void *opaque) > +{ > + struct MultiFDDSSaveThreadData *data = opaque; > + int ret; > + > + ret = data->hdlr(data->idstr, data->instance_id, &send_threads_abort, > + data->handler_opaque); I thought we discussed somewhere and the plan was we could use Error** here to report errors. Would that still make sense, or maybe I lost some context? Meanwhile, I still feel uneasy on having these globals (send_threads_abort, send_threads_ret). Can we make MultiFDDSSaveThreadData the only interface between migration and the threads impl? So I wonder if it can be: ret = data->hdlr(data); With extended struct like this (I added thread_error and thread_quit): struct MultiFDDSSaveThreadData { SaveLiveCompletePrecopyThreadHandler hdlr; char *idstr; uint32_t instance_id; void *handler_opaque; /* * Should be NULL when struct passed over to thread, the thread should * set this if the handler would return false. It must be kept NULL if * the handler returned true / success. */ Error *thread_error; /* * Migration core would set this when it wants to notify thread to * quit, for example, when error occured in other threads, or migration is * cancelled by the user. */ bool thread_quit; }; Then if any multifd_device_state_save_thread() failed, for example, it should notify all threads to quit by setting thread_quit, instead of relying on yet another global variable to show migration needs to quit. Thanks, > + if (ret && !qatomic_read(&send_threads_ret)) { > + /* > + * Racy with the above read but that's okay - which thread error > + * return we report is purely arbitrary anyway. > + */ > + qatomic_set(&send_threads_ret, ret); > + } > + > + return 0; > +} -- Peter Xu