On Wed, Jan 02, 2019 at 01:07:30PM -0700, Jason Gunthorpe wrote:
> On Wed, Jan 02, 2019 at 09:30:24PM +0200, Leon Romanovsky wrote:
>
> > > struct ib_umad_file {
> > > struct mutex mutex;
> > > struct ib_umad_port *port;
> > > struct list_head recv_list;
> > > struct list_head send_list;
> > > struct list_head port_list;
> > > spinlock_t send_lock;
> > > wait_queue_head_t recv_wait;
> > > struct ib_mad_agent *agent[IB_UMAD_MAX_AGENTS];
> > > int agents_dead;
> > > u8 use_pkey_index;
> > > u8 already_used;
> > > };
> > >
> > > No 'ib_umad_device' in there.
> >
> > At the beginning of ib_umad_close(), there is a line:
> > struct ib_umad_device *dev = file->port->umad_dev;
> >
> > Because "dev" is not used before ib_umad_dev_put(), compiler probably
> > defers evaluation of dev pointer till the end, after "kfree(file);".
>
> C does not allow that kind of re-ordering.
Do you have specific section in mind?
>
> > I don't know what about others, but for us this patch gave two weeks
> > of clean runs without traces, which is not the case without it.
>
> Come up with an explanation why it works then?
We always have bug in that area and my kfree() added the "old" delay?
Thanks
>
> Thanks
> Jason
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