Re: [PATCH] drm/i915: Don't enable hwmon for selftests

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Apr 10, 2024 at 10:09:32PM -0700, Dixit, Ashutosh wrote:
> On Wed, 10 Apr 2024 04:42:46 -0700, Ville Syrjälä wrote:
> >
> > On Tue, Apr 09, 2024 at 09:28:55PM -0700, Ashutosh Dixit wrote:
> > > There are no hwmon selftests so there is no need to enable hwmon for
> > > selftests. So enable hwmon only for real driver load.
> > >
> > > Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10366
> > > Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
> >
> > Why are we adding duct tape instead of fixing it properly?
> 
> Yeah pretty much what I said here myself:
> 
> https://patchwork.freedesktop.org/patch/588585/?series=132243&rev=1#comment_1071014
> 
> The issue has been difficult to root-cause. My last effort can be seen here:
> 
> https://patchwork.freedesktop.org/patch/584859/?series=131630&rev=1#comment_1067888
> 
> Though Badal went further and saw that occasionaly the memory would get
> freed first and hwmon would get unregistered as much as 2 seconds later,
> which will cause the crash if anyone touched hwmon sysfs in those final 2
> seconds. So not sure what is causing that 2 second delay.

Sounds like someone holding a sysfs file/etc. open. Should be trivial
to do that by hand and see what happens.

> 
> I am not sure if it is worth root-causing further. I am pretty sure if we
> get rid of the devm_ stuff, that will fix the issue too. So if this patch
> is not acceptable, we could just go that route (get rid of devm_ in hwmon).
> 
> Thanks.
> --
> Ashutosh
> 
> > > ---
> > >  drivers/gpu/drm/i915/i915_driver.c | 16 ++++++++++++++--
> > >  1 file changed, 14 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
> > > index 9ee902d5b72c..6fa6d2c8109f 100644
> > > --- a/drivers/gpu/drm/i915/i915_driver.c
> > > +++ b/drivers/gpu/drm/i915/i915_driver.c
> > > @@ -94,6 +94,7 @@
> > >  #include "i915_memcpy.h"
> > >  #include "i915_perf.h"
> > >  #include "i915_query.h"
> > > +#include "i915_selftest.h"
> > >  #include "i915_suspend.h"
> > >  #include "i915_switcheroo.h"
> > >  #include "i915_sysfs.h"
> > > @@ -589,6 +590,15 @@ static void i915_driver_hw_remove(struct drm_i915_private *dev_priv)
> > >		pci_disable_msi(pdev);
> > >  }
> > >
> > > +static bool is_selftest(void)
> > > +{
> > > +#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
> > > +	return i915_selftest.live || i915_selftest.perf || i915_selftest.mock;
> > > +#else
> > > +	return false;
> > > +#endif
> > > +}
> > > +
> > >  /**
> > >   * i915_driver_register - register the driver with the rest of the system
> > >   * @dev_priv: device private
> > > @@ -624,7 +634,8 @@ static void i915_driver_register(struct drm_i915_private *dev_priv)
> > >
> > >	intel_pxp_debugfs_register(dev_priv->pxp);
> > >
> > > -	i915_hwmon_register(dev_priv);
> > > +	if (!is_selftest())
> > > +		i915_hwmon_register(dev_priv);
> > >
> > >	intel_display_driver_register(dev_priv);
> > >
> > > @@ -660,7 +671,8 @@ static void i915_driver_unregister(struct drm_i915_private *dev_priv)
> > >	for_each_gt(gt, dev_priv, i)
> > >		intel_gt_driver_unregister(gt);
> > >
> > > -	i915_hwmon_unregister(dev_priv);
> > > +	if (!is_selftest())
> > > +		i915_hwmon_unregister(dev_priv);
> > >
> > >	i915_perf_unregister(dev_priv);
> > >	i915_pmu_unregister(dev_priv);
> > > --
> > > 2.41.0
> >
> > --
> > Ville Syrjälä
> > Intel

-- 
Ville Syrjälä
Intel