On Thu, 2022-12-08 at 14:32 +0200, Jani Nikula wrote:
> On Thu, 08 Dec 2022, Andrzej Hajda <andrzej.hajda@xxxxxxxxx> wrote:
> > Simplify the code.
>
> Personally, I absolutely hate fetch_and_zero().
>
> I understand the point, but there are two main traps:
>
> First, the name implies atomicity, which there is none at all.
>
> Second, the name implies it's part of a kernel core header, which it
> isn't, and this just amplifies the first point.
>
> It's surprising and misleading, and those are not things I like about
> interfaces in the kernel.
>
> I would not like to see this proliferate. If fetch_and_zero() was
> atomic
> *and* part of a core kernel header, it would be a different matter.
> But
> I don't think that's going to happen, exactly because it won't be
> atomic
> and the name implies it is.
+1 here.
Please let's go the other way around and try to kill macros like this.
we either kill or we ensure this gets accepted in the core kernel
libraries.
>
>
> BR,
> Jani.
>
>
> >
> > Signed-off-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/display/intel_hotplug.c | 12 ++++--------
> > 1 file changed, 4 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_hotplug.c
> > b/drivers/gpu/drm/i915/display/intel_hotplug.c
> > index 907ab7526cb478..2972d7533da44e 100644
> > --- a/drivers/gpu/drm/i915/display/intel_hotplug.c
> > +++ b/drivers/gpu/drm/i915/display/intel_hotplug.c
> > @@ -304,10 +304,8 @@ static void i915_digport_work_func(struct
> > work_struct *work)
> > u32 old_bits = 0;
> >
> > spin_lock_irq(&dev_priv->irq_lock);
> > - long_port_mask = dev_priv->display.hotplug.long_port_mask;
> > - dev_priv->display.hotplug.long_port_mask = 0;
> > - short_port_mask = dev_priv-
> > >display.hotplug.short_port_mask;
> > - dev_priv->display.hotplug.short_port_mask = 0;
> > + long_port_mask = fetch_and_zero(&dev_priv-
> > >display.hotplug.long_port_mask);
> > + short_port_mask = fetch_and_zero(&dev_priv-
> > >display.hotplug.short_port_mask);
> > spin_unlock_irq(&dev_priv->irq_lock);
> >
> > for_each_intel_encoder(&dev_priv->drm, encoder) {
> > @@ -379,10 +377,8 @@ static void i915_hotplug_work_func(struct
> > work_struct *work)
> >
> > spin_lock_irq(&dev_priv->irq_lock);
> >
> > - hpd_event_bits = dev_priv->display.hotplug.event_bits;
> > - dev_priv->display.hotplug.event_bits = 0;
> > - hpd_retry_bits = dev_priv->display.hotplug.retry_bits;
> > - dev_priv->display.hotplug.retry_bits = 0;
> > + hpd_event_bits = fetch_and_zero(&dev_priv-
> > >display.hotplug.event_bits);
> > + hpd_retry_bits = fetch_and_zero(&dev_priv-
> > >display.hotplug.retry_bits);
> >
> > /* Enable polling for connectors which had HPD IRQ storms
> > */
> > intel_hpd_irq_storm_switch_to_polling(dev_priv);
>
