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[82.30.61.225]) by smtp.gmail.com with ESMTPSA id z6-20020a056000110600b00207aa9eec98sm2323200wrw.30.2022.04.21.07.13.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Apr 2022 07:13:36 -0700 (PDT) Date: Thu, 21 Apr 2022 15:13:34 +0100 From: "Dr. David Alan Gilbert" To: qemu-devel@nongnu.org, quintela@redhat.com, peterx@redhat.com, leobras@redhat.com Subject: Re: [PATCH] migration: Read state once Message-ID: References: <20220413113329.103696-1-dgilbert@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220413113329.103696-1-dgilbert@redhat.com> User-Agent: Mutt/2.2.1 (2022-02-19) 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: pkrempa@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Dr. David Alan Gilbert (git) (dgilbert@redhat.com) wrote: > From: "Dr. David Alan Gilbert" > > The 'status' field for the migration is updated normally using > an atomic operation from the migration thread. > Most readers of it aren't that careful, and in most cases it doesn't > matter. > > In query_migrate->fill_source_migration_info the 'state' > is read twice; the first time to decide which state fields to fill in, > and then secondly to copy the state to the status field; that can end up > with a status that's inconsistent; e.g. setting up the fields > for 'setup' and then having an 'active' status. In that case > libvirt gets upset by the lack of ram info. > The symptom is: > libvirt.libvirtError: internal error: migration was active, but no RAM info was set > > Read the state exactly once in fill_source_migration_info. > > This is a possible fix for: > https://bugzilla.redhat.com/show_bug.cgi?id=2074205 > > Signed-off-by: Dr. David Alan Gilbert Queued > --- > migration/migration.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/migration/migration.c b/migration/migration.c > index 695f0f2900..811c584619 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -1073,6 +1073,7 @@ static void populate_disk_info(MigrationInfo *info) > static void fill_source_migration_info(MigrationInfo *info) > { > MigrationState *s = migrate_get_current(); > + int state = qatomic_read(&s->state); > GSList *cur_blocker = migration_blockers; > > info->blocked_reasons = NULL; > @@ -1092,7 +1093,7 @@ static void fill_source_migration_info(MigrationInfo *info) > } > info->has_blocked_reasons = info->blocked_reasons != NULL; > > - switch (s->state) { > + switch (state) { > case MIGRATION_STATUS_NONE: > /* no migration has happened ever */ > /* do not overwrite destination migration status */ > @@ -1137,7 +1138,7 @@ static void fill_source_migration_info(MigrationInfo *info) > info->has_status = true; > break; > } > - info->status = s->state; > + info->status = state; > } > > typedef enum WriteTrackingSupport { > -- > 2.35.1 > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK