Re: [PATCH v3 1/2] iommu/arm-smmu-v3: Print better events records

[Jason Gunthorpe <jgg@ziepe.ca>]

On Mon, Sep 30, 2024 at 12:15:10PM -0700, Nicolin Chen wrote:
> > +static void arm_smmu_get_evt_info(struct arm_smmu_device *smmu, u64 *evt,
> > +                                 struct arm_smmu_event *event)
> > +{
> > +       mutex_lock(&smmu->streams_mutex);
> > +       event->master = arm_smmu_find_master(smmu, event->sid);
> > +       mutex_unlock(&smmu->streams_mutex);
> > +
> > +       if (event->master)
> > +               event->master_name = dev_name(event->master->dev);
> > +       else
> > +               event->master_name = "(unassigned sid)";
> 
> Likely safer for dev_name to be in the mutex too.

The result of arm_smmu_find_master() should not leave the lock, and
dev_name()'s result can't leave the lock either, at least not with out
some refcounting on the struct device.

Jason