On Fri, Dec 11, 2015 at 11:33:02AM +0000, Chris Wilson wrote:
> In the reset_counter, we use two bits to track a GPU hang and reset. The
> low bit is a "reset-in-progress" flag that we set to signal when we need
> to break waiters in order for the recovery task to grab the mutex. As
> soon as the recovery task has the mutex, we can clear that flag (which
> we do by incrementing the reset_counter thereby incrementing the gobal
> reset epoch). By clearing that flag when the recovery task holds the
> struct_mutex, we can forgo a second flag that simply tells GEM to ignore
> the "reset-in-progress" flag.
>
> The second flag we store in the reset_counter is whether the
> reset failed and we consider the GPU terminally wedged. Whilst this flag
> is set, all access to the GPU (at least through GEM rather than direct mmio
> access) is verboten.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_debugfs.c | 4 ++--
> drivers/gpu/drm/i915/i915_drv.c | 39 ++++++++++++++++++++++---------------
> drivers/gpu/drm/i915/i915_drv.h | 3 ---
> drivers/gpu/drm/i915/i915_gem.c | 27 +++++++++----------------
> drivers/gpu/drm/i915/i915_irq.c | 21 ++------------------
> 5 files changed, 36 insertions(+), 58 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index c26a4c087f49..d5f66bbdb160 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -4672,7 +4672,7 @@ i915_wedged_get(void *data, u64 *val)
> struct drm_device *dev = data;
> struct drm_i915_private *dev_priv = dev->dev_private;
>
> - *val = i915_reset_counter(&dev_priv->gpu_error);
> + *val = i915_terminally_wedged(&dev_priv->gpu_error);
>
> return 0;
> }
> @@ -4691,7 +4691,7 @@ i915_wedged_set(void *data, u64 val)
> * while it is writing to 'i915_wedged'
> */
>
> - if (i915_reset_in_progress_or_wedged(&dev_priv->gpu_error))
> + if (i915_reset_in_progress(&dev_priv->gpu_error))
> return -EAGAIN;
>
> intel_runtime_pm_get(dev_priv);
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 8ddfcce92cf1..8bdc51bc00a4 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -858,23 +858,32 @@ int i915_resume_switcheroo(struct drm_device *dev)
> int i915_reset(struct drm_device *dev)
> {
> struct drm_i915_private *dev_priv = dev->dev_private;
> - bool simulated;
> + struct i915_gpu_error *error = &dev_priv->gpu_error;
> + unsigned reset_counter;
> int ret;
>
> intel_reset_gt_powersave(dev);
>
> mutex_lock(&dev->struct_mutex);
>
> - i915_gem_reset(dev);
> + /* Clear any previous failed attempts at recovery. Time to try again. */
> + atomic_andnot(I915_WEDGED, &error->reset_counter);
>
> - simulated = dev_priv->gpu_error.stop_rings != 0;
> + /* Clear the reset-in-progress flag and increment the reset epoch. */
> + reset_counter = atomic_inc_return(&error->reset_counter);
> + if (WARN_ON(__i915_reset_in_progress(reset_counter))) {
> + ret = -EIO;
> + goto error;
> + }
> +
> + i915_gem_reset(dev);
>
> ret = intel_gpu_reset(dev);
>
> /* Also reset the gpu hangman. */
> - if (simulated) {
> + if (error->stop_rings != 0) {
> DRM_INFO("Simulated gpu hang, resetting stop_rings\n");
> - dev_priv->gpu_error.stop_rings = 0;
> + error->stop_rings = 0;
> if (ret == -ENODEV) {
> DRM_INFO("Reset not implemented, but ignoring "
> "error for simulated gpu hangs\n");
> @@ -887,8 +896,7 @@ int i915_reset(struct drm_device *dev)
>
> if (ret) {
> DRM_ERROR("Failed to reset chip: %i\n", ret);
> - mutex_unlock(&dev->struct_mutex);
> - return ret;
> + goto error;
> }
>
> intel_overlay_reset(dev_priv);
> @@ -907,20 +915,14 @@ int i915_reset(struct drm_device *dev)
> * was running at the time of the reset (i.e. we weren't VT
> * switched away).
> */
> -
> - /* Used to prevent gem_check_wedged returning -EAGAIN during gpu reset */
> - dev_priv->gpu_error.reload_in_reset = true;
> -
> ret = i915_gem_init_hw(dev);
> -
> - dev_priv->gpu_error.reload_in_reset = false;
> -
> - mutex_unlock(&dev->struct_mutex);
> if (ret) {
> DRM_ERROR("Failed hw init on reset %d\n", ret);
> - return ret;
> + goto error;
> }
>
> + mutex_unlock(&dev->struct_mutex);
> +
> /*
> * rps/rc6 re-init is necessary to restore state lost after the
> * reset and the re-install of gt irqs. Skip for ironlake per
> @@ -931,6 +933,11 @@ int i915_reset(struct drm_device *dev)
> intel_enable_gt_powersave(dev);
>
> return 0;
> +
> +error:
> + atomic_or(I915_WEDGED, &error->reset_counter);
> + mutex_unlock(&dev->struct_mutex);
> + return ret;
> }
>
> static int i915_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 466caa0bc043..1043ddd670a5 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1384,9 +1384,6 @@ struct i915_gpu_error {
>
> /* For missed irq/seqno simulation. */
> unsigned int test_irq_rings;
> -
> - /* Used to prevent gem_check_wedged returning -EAGAIN during gpu reset */
> - bool reload_in_reset;
> };
>
> enum modeset_restore {
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 0b3e0534baa3..27e617b76418 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -85,9 +85,7 @@ i915_gem_wait_for_error(struct i915_gpu_error *error)
> {
> int ret;
>
> -#define EXIT_COND (!i915_reset_in_progress_or_wedged(error) || \
> - i915_terminally_wedged(error))
> - if (EXIT_COND)
> + if (!i915_reset_in_progress(error))
> return 0;
>
> /*
> @@ -96,17 +94,16 @@ i915_gem_wait_for_error(struct i915_gpu_error *error)
> * we should simply try to bail out and fail as gracefully as possible.
> */
> ret = wait_event_interruptible_timeout(error->reset_queue,
> - EXIT_COND,
> + !i915_reset_in_progress(error),
> 10*HZ);
> if (ret == 0) {
> DRM_ERROR("Timed out waiting for the gpu reset to complete\n");
> return -EIO;
> } else if (ret < 0) {
> return ret;
> + } else {
> + return 0;
> }
> -#undef EXIT_COND
> -
> - return 0;
> }
>
> int i915_mutex_lock_interruptible(struct drm_device *dev)
> @@ -1114,22 +1111,16 @@ i915_gem_check_wedge(struct i915_gpu_error *error,
> bool interruptible)
> {
> if (i915_reset_in_progress_or_wedged(error)) {
> + /* Recovery complete, but the reset failed ... */
> + if (i915_terminally_wedged(error))
> + return -EIO;
> +
> /* Non-interruptible callers can't handle -EAGAIN, hence return
> * -EIO unconditionally for these. */
> if (!interruptible)
> return -EIO;
>
> - /* Recovery complete, but the reset failed ... */
> - if (i915_terminally_wedged(error))
> - return -EIO;
> -
> - /*
> - * Check if GPU Reset is in progress - we need intel_ring_begin
> - * to work properly to reinit the hw state while the gpu is
> - * still marked as reset-in-progress. Handle this with a flag.
> - */
> - if (!error->reload_in_reset)
> - return -EAGAIN;
> + return -EAGAIN;
> }
>
> return 0;
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 60dff3f89531..88206c0404d7 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -2434,7 +2434,6 @@ static void i915_error_wake_up(struct drm_i915_private *dev_priv,
> static void i915_reset_and_wakeup(struct drm_device *dev)
> {
> struct drm_i915_private *dev_priv = to_i915(dev);
> - struct i915_gpu_error *error = &dev_priv->gpu_error;
> char *error_event[] = { I915_ERROR_UEVENT "=1", NULL };
> char *reset_event[] = { I915_RESET_UEVENT "=1", NULL };
> char *reset_done_event[] = { I915_ERROR_UEVENT "=0", NULL };
> @@ -2452,7 +2451,7 @@ static void i915_reset_and_wakeup(struct drm_device *dev)
> * the reset in-progress bit is only ever set by code outside of this
> * work we don't need to worry about any other races.
> */
> - if (i915_reset_in_progress_or_wedged(error) && !i915_terminally_wedged(error)) {
> + if (i915_reset_in_progress(&dev_priv->gpu_error)) {
> DRM_DEBUG_DRIVER("resetting chip\n");
> kobject_uevent_env(&dev->primary->kdev->kobj, KOBJ_CHANGE,
> reset_event);
> @@ -2480,25 +2479,9 @@ static void i915_reset_and_wakeup(struct drm_device *dev)
>
> intel_runtime_pm_put(dev_priv);
>
> - if (ret == 0) {
> - /*
> - * After all the gem state is reset, increment the reset
> - * counter and wake up everyone waiting for the reset to
> - * complete.
> - *
> - * Since unlock operations are a one-sided barrier only,
> - * we need to insert a barrier here to order any seqno
> - * updates before
> - * the counter increment.
> - */
> - smp_mb__before_atomic();
> - atomic_inc(&dev_priv->gpu_error.reset_counter);
> -
> + if (ret == 0)
> kobject_uevent_env(&dev->primary->kdev->kobj,
> KOBJ_CHANGE, reset_done_event);
> - } else {
> - atomic_or(I915_WEDGED, &error->reset_counter);
> - }
>
> /*
> * Note: The wake_up also serves as a memory barrier so that
> --
> 2.6.3
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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