On Mon, Jul 22, 2019 at 02:21:18PM +0300, Gal Pressman wrote:
> On 22/07/2019 12:15, Leon Romanovsky wrote:
> > On Mon, Jul 22, 2019 at 11:10:51AM +0300, Gal Pressman wrote:
> >> Hi all,
> >>
> >> I'm seeing memory leaks when running tests with valgrind memcheck tool [1]. It
> >> seems like it's caused due to verbs_device refcount never reaching zero.
> >>
> >> Last related commit is 8125fdeb69bb ("verbs: Avoid ibv_device memory leak"),
> >> which seems like it should prevent this issue - but I'm not sure it covers all
> >> cases.
> >>
> >> When calling ibv_get_device_list, try_driver will eventually get called and set
> >> the device refcount to one. The refcount for each device will be increased when
> >> iterating the devices list, and on each verbs_init_context call.
> >>
> >> In the free flow, the refcount is decreased on verbs_uninit_context and when
> >> iterating the devices list - which brings the refcount back to one, as initially
> >> set by try_driver (hence uninit_device isn't called).
> >>
> >> Is there a reason for initializing refcount to one instead of zero? According to
> >> the cited commit the reference count should be decreased when the device no
> >> longer exists in the sysfs, but the device isn't necessarily removed from the sysfs.
> >
> > Such scheme allows us to avoid rdma-core provider reinitialization every
> > time application "plays" with ibv_get_device_list(). Anyway, the rdma-core
> > library (libibverbs) won't be unloaded till dclose() is called and glibc
> > reference count won't reach zero, so we don't need to release provider
> > till that point of time too.
>
> So you consider these valgrind errors false alarms?
Yes, valgrind checks executed code and unlikely to check unload sequence.
In your case, the unload code wasn't called at all.
Thanks
