| Message ID | 20210622024236.600347-1-leobras@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v1,1/1] migration: Unregister yank if migration setup fails | expand |
On Mon, Jun 21, 2021 at 11:42:36PM -0300, Leonardo Bras wrote: > Currently, if a qemu instance is started with "-incoming defer" and > an incorect parameter is passed to "migrate_incoming", it will print the > expected error and reply with "duplicate yank instance" for any upcoming > "migrate_incoming" command. > > This renders current qemu process unusable, and requires a new qemu > process to be started before accepting a migration. > > This is caused by a yank_register_instance() that happens in > qemu_start_incoming_migration() but is never reverted if any error > happens. > > Solves this by unregistering the instance if anything goes wrong > in the function, allowing a new "migrate_incoming" command to be > accepted. > > Fixes: b5eea99ec2f ("migration: Add yank feature", 2021-01-13) > Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1974366 > Signed-off-by: Leonardo Bras <leobras@redhat.com> > > --- > migration/migration.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/migration/migration.c b/migration/migration.c > index 4228635d18..ddcf9e1868 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -474,9 +474,13 @@ static void qemu_start_incoming_migration(const char *uri, Error **errp) > } else if (strstart(uri, "fd:", &p)) { > fd_start_incoming_migration(p, errp); > } else { > - yank_unregister_instance(MIGRATION_YANK_INSTANCE); > error_setg(errp, "unknown migration protocol: %s", uri); > } > + > + if (*errp) { > + yank_unregister_instance(MIGRATION_YANK_INSTANCE); > + } > + > } Yes, looks right to me: Reviewed-by: Peter Xu <peterx@redhat.com>
On Tue, Jun 22, 2021 at 2:38 PM Peter Xu <peterx@redhat.com> wrote: [...] > Yes, looks right to me: > > Reviewed-by: Peter Xu <peterx@redhat.com> > > -- > Peter Xu Thanks Peter!
* Leonardo Bras (leobras@redhat.com) wrote: > Currently, if a qemu instance is started with "-incoming defer" and > an incorect parameter is passed to "migrate_incoming", it will print the > expected error and reply with "duplicate yank instance" for any upcoming > "migrate_incoming" command. > > This renders current qemu process unusable, and requires a new qemu > process to be started before accepting a migration. > > This is caused by a yank_register_instance() that happens in > qemu_start_incoming_migration() but is never reverted if any error > happens. > > Solves this by unregistering the instance if anything goes wrong > in the function, allowing a new "migrate_incoming" command to be > accepted. > > Fixes: b5eea99ec2f ("migration: Add yank feature", 2021-01-13) > Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1974366 > Signed-off-by: Leonardo Bras <leobras@redhat.com> > > --- > migration/migration.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/migration/migration.c b/migration/migration.c > index 4228635d18..ddcf9e1868 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -474,9 +474,13 @@ static void qemu_start_incoming_migration(const char *uri, Error **errp) > } else if (strstart(uri, "fd:", &p)) { > fd_start_incoming_migration(p, errp); > } else { > - yank_unregister_instance(MIGRATION_YANK_INSTANCE); > error_setg(errp, "unknown migration protocol: %s", uri); > } > + > + if (*errp) { > + yank_unregister_instance(MIGRATION_YANK_INSTANCE); > + } My understanding is that testing *errp isn't allowed, because it's legal to pass NULL to ignore errors, or legal to pass &error_abort to mean that any error you do hit will cause the process to assert; so you need to have something separate you can test. Dave > } > > static void process_incoming_migration_bh(void *opaque) > -- > 2.32.0 >
* Dr. David Alan Gilbert (dgilbert@redhat.com) wrote: > * Leonardo Bras (leobras@redhat.com) wrote: > > Currently, if a qemu instance is started with "-incoming defer" and > > an incorect parameter is passed to "migrate_incoming", it will print the > > expected error and reply with "duplicate yank instance" for any upcoming > > "migrate_incoming" command. > > > > This renders current qemu process unusable, and requires a new qemu > > process to be started before accepting a migration. > > > > This is caused by a yank_register_instance() that happens in > > qemu_start_incoming_migration() but is never reverted if any error > > happens. > > > > Solves this by unregistering the instance if anything goes wrong > > in the function, allowing a new "migrate_incoming" command to be > > accepted. > > > > Fixes: b5eea99ec2f ("migration: Add yank feature", 2021-01-13) > > Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1974366 > > Signed-off-by: Leonardo Bras <leobras@redhat.com> > > > > --- > > migration/migration.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/migration/migration.c b/migration/migration.c > > index 4228635d18..ddcf9e1868 100644 > > --- a/migration/migration.c > > +++ b/migration/migration.c > > @@ -474,9 +474,13 @@ static void qemu_start_incoming_migration(const char *uri, Error **errp) > > } else if (strstart(uri, "fd:", &p)) { > > fd_start_incoming_migration(p, errp); > > } else { > > - yank_unregister_instance(MIGRATION_YANK_INSTANCE); > > error_setg(errp, "unknown migration protocol: %s", uri); > > } > > + > > + if (*errp) { > > + yank_unregister_instance(MIGRATION_YANK_INSTANCE); > > + } > > My understanding is that testing *errp isn't allowed, because > it's legal to pass NULL to ignore errors, or legal to pass > &error_abort to mean that any error you do hit will cause the > process to assert; so you need to have something separate you can test. Ah, and armbru points out there's a 'new' mechanism to make it safe; you need to use ERRP_GUARD, see include/qapi/error.h if you want to be able to test it. Dave > Dave > > > } > > > > static void process_incoming_migration_bh(void *opaque) > > -- > > 2.32.0 > > > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
On Thu, Jun 24, 2021 at 06:14:39PM +0100, Dr. David Alan Gilbert wrote: > * Leonardo Bras (leobras@redhat.com) wrote: > > Currently, if a qemu instance is started with "-incoming defer" and > > an incorect parameter is passed to "migrate_incoming", it will print the > > expected error and reply with "duplicate yank instance" for any upcoming > > "migrate_incoming" command. > > > > This renders current qemu process unusable, and requires a new qemu > > process to be started before accepting a migration. > > > > This is caused by a yank_register_instance() that happens in > > qemu_start_incoming_migration() but is never reverted if any error > > happens. > > > > Solves this by unregistering the instance if anything goes wrong > > in the function, allowing a new "migrate_incoming" command to be > > accepted. > > > > Fixes: b5eea99ec2f ("migration: Add yank feature", 2021-01-13) > > Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1974366 > > Signed-off-by: Leonardo Bras <leobras@redhat.com> > > > > --- > > migration/migration.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/migration/migration.c b/migration/migration.c > > index 4228635d18..ddcf9e1868 100644 > > --- a/migration/migration.c > > +++ b/migration/migration.c > > @@ -474,9 +474,13 @@ static void qemu_start_incoming_migration(const char *uri, Error **errp) > > } else if (strstart(uri, "fd:", &p)) { > > fd_start_incoming_migration(p, errp); > > } else { > > - yank_unregister_instance(MIGRATION_YANK_INSTANCE); > > error_setg(errp, "unknown migration protocol: %s", uri); > > } > > + > > + if (*errp) { > > + yank_unregister_instance(MIGRATION_YANK_INSTANCE); > > + } > > My understanding is that testing *errp isn't allowed, because > it's legal to pass NULL to ignore errors, or legal to pass > &error_abort to mean that any error you do hit will cause the > process to assert; so you need to have something separate you can test. Per my understanding error_abort should be fine, as the value of error_abort is still NULL (in error_setg() we only check against &error_abort as the pointer, and its value seems to be better always be NULL..). But indeed at least we need "errp && *errp", but that won't capture the case when errp==NULL. So I think we may need to define a local error, check here when unregister yank, and do error_propagate() before return..
diff --git a/migration/migration.c b/migration/migration.c index 4228635d18..ddcf9e1868 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -474,9 +474,13 @@ static void qemu_start_incoming_migration(const char *uri, Error **errp) } else if (strstart(uri, "fd:", &p)) { fd_start_incoming_migration(p, errp); } else { - yank_unregister_instance(MIGRATION_YANK_INSTANCE); error_setg(errp, "unknown migration protocol: %s", uri); } + + if (*errp) { + yank_unregister_instance(MIGRATION_YANK_INSTANCE); + } + } static void process_incoming_migration_bh(void *opaque)
Currently, if a qemu instance is started with "-incoming defer" and an incorect parameter is passed to "migrate_incoming", it will print the expected error and reply with "duplicate yank instance" for any upcoming "migrate_incoming" command. This renders current qemu process unusable, and requires a new qemu process to be started before accepting a migration. This is caused by a yank_register_instance() that happens in qemu_start_incoming_migration() but is never reverted if any error happens. Solves this by unregistering the instance if anything goes wrong in the function, allowing a new "migrate_incoming" command to be accepted. Fixes: b5eea99ec2f ("migration: Add yank feature", 2021-01-13) Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1974366 Signed-off-by: Leonardo Bras <leobras@redhat.com> --- migration/migration.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)