* [PATCH v1 1/1] migration: Unregister yank if migration setup fails
@ 2021-06-22 2:42 Leonardo Bras
2021-06-22 17:38 ` Peter Xu
2021-06-24 17:14 ` Dr. David Alan Gilbert
0 siblings, 2 replies; 6+ messages in thread
From: Leonardo Bras @ 2021-06-22 2:42 UTC (permalink / raw)
To: Juan Quintela, Dr. David Alan Gilbert, Lukas Straub, Peter Xu
Cc: Leonardo Bras, qemu-devel
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);
+ }
+
}
static void process_incoming_migration_bh(void *opaque)
--
2.32.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v1 1/1] migration: Unregister yank if migration setup fails
2021-06-22 2:42 [PATCH v1 1/1] migration: Unregister yank if migration setup fails Leonardo Bras
@ 2021-06-22 17:38 ` Peter Xu
2021-06-22 23:31 ` Leonardo Bras Soares Passos
2021-06-24 17:14 ` Dr. David Alan Gilbert
1 sibling, 1 reply; 6+ messages in thread
From: Peter Xu @ 2021-06-22 17:38 UTC (permalink / raw)
To: Leonardo Bras
Cc: qemu-devel, Lukas Straub, Dr. David Alan Gilbert, Juan Quintela
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>
--
Peter Xu
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v1 1/1] migration: Unregister yank if migration setup fails
2021-06-22 17:38 ` Peter Xu
@ 2021-06-22 23:31 ` Leonardo Bras Soares Passos
0 siblings, 0 replies; 6+ messages in thread
From: Leonardo Bras Soares Passos @ 2021-06-22 23:31 UTC (permalink / raw)
To: Peter Xu; +Cc: qemu-devel, Lukas Straub, Dr. David Alan Gilbert, Juan Quintela
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!
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v1 1/1] migration: Unregister yank if migration setup fails
2021-06-22 2:42 [PATCH v1 1/1] migration: Unregister yank if migration setup fails Leonardo Bras
2021-06-22 17:38 ` Peter Xu
@ 2021-06-24 17:14 ` Dr. David Alan Gilbert
2021-06-24 17:20 ` Dr. David Alan Gilbert
2021-06-24 17:29 ` Peter Xu
1 sibling, 2 replies; 6+ messages in thread
From: Dr. David Alan Gilbert @ 2021-06-24 17:14 UTC (permalink / raw)
To: Leonardo Bras; +Cc: Lukas Straub, qemu-devel, Peter Xu, Juan Quintela
* 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 / Manchester, UK
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v1 1/1] migration: Unregister yank if migration setup fails
2021-06-24 17:14 ` Dr. David Alan Gilbert
@ 2021-06-24 17:20 ` Dr. David Alan Gilbert
2021-06-24 17:29 ` Peter Xu
1 sibling, 0 replies; 6+ messages in thread
From: Dr. David Alan Gilbert @ 2021-06-24 17:20 UTC (permalink / raw)
To: Leonardo Bras; +Cc: Lukas Straub, qemu-devel, Peter Xu, Juan Quintela
* 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
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v1 1/1] migration: Unregister yank if migration setup fails
2021-06-24 17:14 ` Dr. David Alan Gilbert
2021-06-24 17:20 ` Dr. David Alan Gilbert
@ 2021-06-24 17:29 ` Peter Xu
1 sibling, 0 replies; 6+ messages in thread
From: Peter Xu @ 2021-06-24 17:29 UTC (permalink / raw)
To: Dr. David Alan Gilbert
Cc: Lukas Straub, Leonardo Bras, qemu-devel, Juan Quintela
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..
--
Peter Xu
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-06-24 17:34 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-06-22 2:42 [PATCH v1 1/1] migration: Unregister yank if migration setup fails Leonardo Bras
2021-06-22 17:38 ` Peter Xu
2021-06-22 23:31 ` Leonardo Bras Soares Passos
2021-06-24 17:14 ` Dr. David Alan Gilbert
2021-06-24 17:20 ` Dr. David Alan Gilbert
2021-06-24 17:29 ` Peter Xu
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