On Mon, 25 Jul 2011 10:10:29 -0700
Keith Packard <keithp@xxxxxxxxxx> wrote:
> Hotplug detection is a mode setting operation and must hold the
> struct_mutex or risk colliding with other mode setting operations.
>
> In particular, the display port hotplug function attempts to re-train
> the link if the monitor is supposed to be running when plugged back
> in. If that happens while mode setting is underway, the link will get
> scrambled, leaving it in an inconsistent state.
>
> Signed-off-by: Keith Packard <keithp@xxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_irq.c | 3 +++
> 1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 3b03f85..5fe8f28 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -306,12 +306,15 @@ static void i915_hotplug_work_func(struct work_struct *work)
> struct drm_mode_config *mode_config = &dev->mode_config;
> struct intel_encoder *encoder;
>
> + mutex_lock(&dev_priv->dev->struct_mutex);
> DRM_DEBUG_KMS("running encoder hotplug functions\n");
>
> list_for_each_entry(encoder, &mode_config->encoder_list, base.head)
> if (encoder->hot_plug)
> encoder->hot_plug(encoder);
>
> + mutex_unlock(&dev_priv->dev->struct_mutex);
> +
> /* Just fire off a uevent and let userspace tell us what to do */
> drm_helper_hpd_irq_event(dev);
> }
yay, sounds like this will fix Andrew's problem and probably lots of
other random DP related failures.
Looks like the ->detect function is similarly protected at the call
site (though one level up in ->fill_modes), so it should be safe.
Looks like all the call sites in the link_status function are safe too.
Reviewed-by: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>
Let's get this one upstream asap. Should probably be cc'd to
stable@xxxxxxxxxx as well.
--
Jesse Barnes, Intel Open Source Technology Center
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