On Thu, Jul 13, 2023 at 12:03:24PM +0100, Richard W.M. Jones wrote:
> On Thu, Jul 13, 2023 at 09:53:58AM +0000, Tage Johansson wrote:
> > Apologize if resending, but I'm not sure my previous email was
> > actually delivered.
> >
> >
> > On 7/12/2023 10:33 PM, Eric Blake wrote:
> >
> >
> > >On Wed, Jul 12, 2023 at 03:19:59PM +0000, Tage Johansson wrote:
> > >>Hello,
> > >>
> > >>
> > >>While writing some tests for the Rust bindings, I discovered a
> > >>memory leak
> > >>with Valgrind due to a completion callback not being freed. More
> > >>specificly,
> > >>the completion callback of `aio_opt_info()` doesn't seem to be if
> > >>`aio_opt_info()` failes. In this case, `aio_opt_info()` was called in the
> > >>connected state, so it should indeed fail, but it should perhaps
> > >>also call
> > >>the free function associated with the callback.
> > >Can you paste the valgrind output showing the leak?
> >
> >
> > The Valgrind output is very Rust specific and only shows the Rust
> > allocations which goes into the completion callback and are lost.
> >
> >
> > But if you apply the following patch (which modifies
> > tests/opt-info.c) you shall see that the completion callback is not
> > called.
Ah. I see. We are testing the synchronous command, but not the aio
counterpart command. That is indeed a hole in the testsuite (even
after my patch yesterday).
> >
> > I have replaced a call to `nbd_opt_info()` with a call to
> > `nbd_aio_opt_info()` and passed in a completion callback which just
> > calls `exit(EXIT_FAILURE)`. So if the completion callback is called
> > the test should fail, which it doesn't, at least not on my machine.
>
> Isn't that OK? Only .free is required to be called.
For the context callback (for opt_set_meta), .callback may be called
zero, one, or multiple times, but .free should be called exactly once.
But for the completion callback, I agree that the docs state that both
.callback and .free should each be called exactly once ("On the other
hand, if a completion callback is supplied (only possible with
asynchronous commands), it will always be reached exactly once, and
the completion callback must not ignore the value pointed to by
C<error>."); we are indeed missing the call to .callback. I'll work
on a patch.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
_______________________________________________
Libguestfs mailing list
Libguestfs@redhat.com
https://listman.redhat.com/mailman/listinfo/libguestfs
