Re: [PATCH v6 2/4] driver core: add deferring probe reason to devices_deferred property

[Grygorii Strashko]

Hi

On 29/06/2020 14:28, Andrzej Hajda wrote:
> Hi Grygorii,
>
> (...)
>
> > >  Â /*
> > >  ÂÂ * deferred_devs_show() - Show the devices in the deferred probe
> > > pending list.
> > >  ÂÂ */
> > > @@ -221,7 +241,8 @@ static int deferred_devs_show(struct seq_file *s,
> > > void *data)
> > >  ÂÂÂÂÂ mutex_lock(&deferred_probe_mutex);
> > >  Â ÂÂÂÂÂ list_for_each_entry(curr, &deferred_probe_pending_list,
> > > deferred_probe)
> > > -ÂÂÂÂÂÂÂ seq_printf(s, "%s\n", dev_name(curr->device));
> > > +ÂÂÂÂÂÂÂ seq_printf(s, "%s\t%s", dev_name(curr->device),
> > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ curr->device->p->deferred_probe_reason ?: "\n");
> > >  Â ÂÂÂÂÂ mutex_unlock(&deferred_probe_mutex);
> >
> > Sry, may be i missing smth, but shouldn't it be optional
> > (CONFIG_DEBUG_FS is probably too generic).
>
> I am not sure what exactly are you referring to, but this patch does not
> add new property, it just extends functionality of existing one.

Sry, needed to be more specific.

You've added  device_set_deferred_probe_reson(dev, &vaf);
which expected to be used on every EPROBE_DEFER in dev_err_probe() in combination with

+       } else {
+               device_set_deferred_probe_reson(dev, &vaf);
                dev_dbg(dev, "error %d: %pV", err, &vaf);

^^ dev_dbg() does not add any runtime overhead during boot unless enabled
+       }

But:

+void device_set_deferred_probe_reson(const struct device *dev, struct va_format *vaf)
+{
+       const char *drv = dev_driver_string(dev);
+
+       mutex_lock(&deferred_probe_mutex);
+
+       kfree(dev->p->deferred_probe_reason);
+       dev->p->deferred_probe_reason = kasprintf(GFP_KERNEL, "%s: %pV", drv, vaf);
+
+       mutex_unlock(&deferred_probe_mutex);
+}

^^ Adds locking, kfree() and kasprintf() for every deferred probe during boot and can't be disabled.

Right?


--
Best regards,
grygorii