[Intel-gfx] [PATCH] drm/probe-helpers: Drop locking from poll_enable
Lyude Paul
lyude at redhat.com
Thu Jan 12 18:08:47 UTC 2017
Fixes locking issues I've witnessed on the W541.
Tested-by: Lyude <lyude at redhat.com>
Reviewed-by: Lyude <lyude at redhat.com>
On Wed, 2017-01-11 at 10:01 +0100, Daniel Vetter wrote:
> It was only needed to protect the connector_list walking, see
>
> commit 8c4ccc4ab6f64e859d4ff8d7c02c2ed2e956e07f
> Author: Daniel Vetter <daniel.vetter at ffwll.ch>
> Date: Thu Jul 9 23:44:26 2015 +0200
>
> drm/probe-helper: Grab mode_config.mutex in poll_init/enable
>
> Unfortunately the commit message of that patch fails to mention that
> the new locking check was for the connector_list.
>
> But that requirement disappeared in
>
> commit c36a3254f7857f1ad9badbe3578ccc92be541a8e
> Author: Daniel Vetter <daniel.vetter at ffwll.ch>
> Date: Thu Dec 15 16:58:43 2016 +0100
>
> drm: Convert all helpers to drm_connector_list_iter
>
> and so we can drop this again.
>
> This fixes a locking inversion on nouveau, where the rpm code needs
> to
> re-enable. But in other places the rpm_get() calls are nested within
> the big modeset locks.
>
> While at it, also improve the kerneldoc for these two functions a
> notch.
>
> v2: Update the kerneldoc even more to explain that these functions
> can't be called concurrently, or bad things happen (Chris).
>
> Cc: Dave Airlie <airlied at gmail.com>
> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
> drivers/gpu/drm/drm_probe_helper.c | 51 ++++++++++++++----------
> ------------
> drivers/gpu/drm/i915/intel_hotplug.c | 4 +--
> include/drm/drm_crtc_helper.h | 1 -
> 3 files changed, 22 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_probe_helper.c
> b/drivers/gpu/drm/drm_probe_helper.c
> index 20f48d1e2785..93381454bdf7 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -115,25 +115,28 @@ static int
> drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
>
> #define DRM_OUTPUT_POLL_PERIOD (10*HZ)
> /**
> - * drm_kms_helper_poll_enable_locked - re-enable output polling.
> + * drm_kms_helper_poll_enable - re-enable output polling.
> * @dev: drm_device
> *
> - * This function re-enables the output polling work without
> - * locking the mode_config mutex.
> + * This function re-enables the output polling work, after it has
> been
> + * temporarily disabled using drm_kms_helper_poll_disable(), for
> example over
> + * suspend/resume.
> *
> - * This is like drm_kms_helper_poll_enable() however it is to be
> - * called from a context where the mode_config mutex is locked
> - * already.
> + * Drivers can call this helper from their device resume
> implementation. It is
> + * an error to call this when the output polling support has not yet
> been set
> + * up.
> + *
> + * Note that calls to enable and disable polling must be strictly
> ordered, which
> + * is automatically the case when they're only call from
> suspend/resume
> + * callbacks.
> */
> -void drm_kms_helper_poll_enable_locked(struct drm_device *dev)
> +void drm_kms_helper_poll_enable(struct drm_device *dev)
> {
> bool poll = false;
> struct drm_connector *connector;
> struct drm_connector_list_iter conn_iter;
> unsigned long delay = DRM_OUTPUT_POLL_PERIOD;
>
> - WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
> -
> if (!dev->mode_config.poll_enabled || !drm_kms_helper_poll)
> return;
>
> @@ -163,7 +166,7 @@ void drm_kms_helper_poll_enable_locked(struct
> drm_device *dev)
> if (poll)
> schedule_delayed_work(&dev-
> >mode_config.output_poll_work, delay);
> }
> -EXPORT_SYMBOL(drm_kms_helper_poll_enable_locked);
> +EXPORT_SYMBOL(drm_kms_helper_poll_enable);
>
> static enum drm_connector_status
> drm_connector_detect(struct drm_connector *connector, bool force)
> @@ -290,7 +293,7 @@ int
> drm_helper_probe_single_connector_modes(struct drm_connector
> *connector,
>
> /* Re-enable polling in case the global poll config changed.
> */
> if (drm_kms_helper_poll != dev->mode_config.poll_running)
> - drm_kms_helper_poll_enable_locked(dev);
> + drm_kms_helper_poll_enable(dev);
>
> dev->mode_config.poll_running = drm_kms_helper_poll;
>
> @@ -484,8 +487,12 @@ static void output_poll_execute(struct
> work_struct *work)
> * This function disables the output polling work.
> *
> * Drivers can call this helper from their device suspend
> implementation. It is
> - * not an error to call this even when output polling isn't enabled
> or arlready
> - * disabled.
> + * not an error to call this even when output polling isn't enabled
> or already
> + * disabled. Polling is re-enabled by calling
> drm_kms_helper_poll_enable().
> + *
> + * Note that calls to enable and disable polling must be strictly
> ordered, which
> + * is automatically the case when they're only call from
> suspend/resume
> + * callbacks.
> */
> void drm_kms_helper_poll_disable(struct drm_device *dev)
> {
> @@ -496,24 +503,6 @@ void drm_kms_helper_poll_disable(struct
> drm_device *dev)
> EXPORT_SYMBOL(drm_kms_helper_poll_disable);
>
> /**
> - * drm_kms_helper_poll_enable - re-enable output polling.
> - * @dev: drm_device
> - *
> - * This function re-enables the output polling work.
> - *
> - * Drivers can call this helper from their device resume
> implementation. It is
> - * an error to call this when the output polling support has not yet
> been set
> - * up.
> - */
> -void drm_kms_helper_poll_enable(struct drm_device *dev)
> -{
> - mutex_lock(&dev->mode_config.mutex);
> - drm_kms_helper_poll_enable_locked(dev);
> - mutex_unlock(&dev->mode_config.mutex);
> -}
> -EXPORT_SYMBOL(drm_kms_helper_poll_enable);
> -
> -/**
> * drm_kms_helper_poll_init - initialize and enable output polling
> * @dev: drm_device
> *
> diff --git a/drivers/gpu/drm/i915/intel_hotplug.c
> b/drivers/gpu/drm/i915/intel_hotplug.c
> index 2ddc9e5842ec..5122d4bfb70e 100644
> --- a/drivers/gpu/drm/i915/intel_hotplug.c
> +++ b/drivers/gpu/drm/i915/intel_hotplug.c
> @@ -182,7 +182,7 @@ static void intel_hpd_irq_storm_disable(struct
> drm_i915_private *dev_priv)
>
> /* Enable polling and queue hotplug re-enabling. */
> if (hpd_disabled) {
> - drm_kms_helper_poll_enable_locked(dev);
> + drm_kms_helper_poll_enable(dev);
> mod_delayed_work(system_wq, &dev_priv-
> >hotplug.reenable_work,
> msecs_to_jiffies(HPD_STORM_REENABLE
> _DELAY));
> }
> @@ -519,7 +519,7 @@ static void i915_hpd_poll_init_work(struct
> work_struct *work)
> drm_connector_list_iter_put(&conn_iter);
>
> if (enabled)
> - drm_kms_helper_poll_enable_locked(dev);
> + drm_kms_helper_poll_enable(dev);
>
> mutex_unlock(&dev->mode_config.mutex);
>
> diff --git a/include/drm/drm_crtc_helper.h
> b/include/drm/drm_crtc_helper.h
> index 982c299e435a..d026f5017c33 100644
> --- a/include/drm/drm_crtc_helper.h
> +++ b/include/drm/drm_crtc_helper.h
> @@ -73,6 +73,5 @@ extern void drm_kms_helper_hotplug_event(struct
> drm_device *dev);
>
> extern void drm_kms_helper_poll_disable(struct drm_device *dev);
> extern void drm_kms_helper_poll_enable(struct drm_device *dev);
> -extern void drm_kms_helper_poll_enable_locked(struct drm_device
> *dev);
>
> #endif
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