From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:32976) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gzJGB-0002w0-H9 for qemu-devel@nongnu.org; Thu, 28 Feb 2019 05:49:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gzJGA-0003qm-ER for qemu-devel@nongnu.org; Thu, 28 Feb 2019 05:49:51 -0500 Received: from mail-wr1-x443.google.com ([2a00:1450:4864:20::443]:43244) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1gzJG9-0003qC-Vj for qemu-devel@nongnu.org; Thu, 28 Feb 2019 05:49:50 -0500 Received: by mail-wr1-x443.google.com with SMTP id d17so21341034wre.10 for ; Thu, 28 Feb 2019 02:49:49 -0800 (PST) References: <20190227164900.16378-1-dgilbert@redhat.com> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: <20190227164900.16378-1-dgilbert@redhat.com> Date: Thu, 28 Feb 2019 10:49:46 +0000 Message-ID: <87ef7skx11.fsf@zen.linaroharston> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH] migration: Cleanup during exit List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert (git)" Cc: qemu-devel@nongnu.org, quintela@redhat.com, peterx@redhat.com Dr. David Alan Gilbert (git) writes: > From: "Dr. David Alan Gilbert" > > Currently we cleanup the migration object as we exit main after the > main_loop finishes; however if there's a migration running things > get messy and we can end up with the migration thread still trying > to access freed structures. > > We now take a ref to the object around the migration thread itself, > so the act of dropping the ref during exit doesn't cause us to lose > the state until the thread quits. > > Cancelling the migration during migration also tries to get the thread > to quit. > > We do this a bit earlier; so hopefully migration gets out of the way > before all the devices etc are freed. > > Signed-off-by: Dr. David Alan Gilbert > Tested-by: Alex Benn=C3=A9e > --- > include/migration/misc.h | 2 +- > migration/migration.c | 10 +++++++++- > vl.c | 7 ++++++- > 3 files changed, 16 insertions(+), 3 deletions(-) > > diff --git a/include/migration/misc.h b/include/migration/misc.h > index 0471e04d1f..6f9df74436 100644 > --- a/include/migration/misc.h > +++ b/include/migration/misc.h > @@ -36,7 +36,7 @@ void dump_vmstate_json_to_file(FILE *out_fp); > > /* migration/migration.c */ > void migration_object_init(void); > -void migration_object_finalize(void); > +void migration_shutdown(void); > void qemu_start_incoming_migration(const char *uri, Error **errp); > bool migration_is_idle(void); > void add_migration_state_change_notifier(Notifier *notify); > diff --git a/migration/migration.c b/migration/migration.c > index e44f77af02..d45561f9b8 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -126,6 +126,7 @@ static bool migration_object_check(MigrationState *ms= , Error **errp); > static int migration_maybe_pause(MigrationState *s, > int *current_active_state, > int new_state); > +static void migrate_fd_cancel(MigrationState *s); > > void migration_object_init(void) > { > @@ -167,8 +168,13 @@ void migration_object_init(void) > } > } > > -void migration_object_finalize(void) > +void migration_shutdown(void) > { > + /* > + * Cancel the current migration - that will (eventually) > + * stop the migration using this structure > + */ > + migrate_fd_cancel(current_migration); > object_unref(OBJECT(current_migration)); > } > > @@ -3134,6 +3140,7 @@ static void *migration_thread(void *opaque) > > rcu_register_thread(); > > + object_ref(OBJECT(s)); > s->iteration_start_time =3D qemu_clock_get_ms(QEMU_CLOCK_REALTIME); > > qemu_savevm_state_header(s->to_dst_file); > @@ -3230,6 +3237,7 @@ static void *migration_thread(void *opaque) > > trace_migration_thread_after_loop(); > migration_iteration_finish(s); > + object_unref(OBJECT(s)); > rcu_unregister_thread(); > return NULL; > } > diff --git a/vl.c b/vl.c > index 2f340686a7..e7f460a114 100644 > --- a/vl.c > +++ b/vl.c > @@ -4579,6 +4579,12 @@ int main(int argc, char **argv, char **envp) > > gdbserver_cleanup(); > > + /* > + * cleaning up the migration object cancels any existing migration > + * try to do this early so that it also stops using devices. > + */ > + migration_shutdown(); > + We do like to vary our language over here, I guess shutdown and cleanup imply subtly different things. FWIW I suspect the gdbserver_cleanup() should be a shutdown ;-) Reviewed-by: Alex Benn=C3=A9e > /* No more vcpu or device emulation activity beyond this point */ > vm_shutdown(); > > @@ -4594,7 +4600,6 @@ int main(int argc, char **argv, char **envp) > monitor_cleanup(); > qemu_chr_cleanup(); > user_creatable_cleanup(); > - migration_object_finalize(); > /* TODO: unref root container, check all devices are ok */ > > return 0; -- Alex Benn=C3=A9e