From 7ae1940014ef77e6389ca95a5a75273c9c4ea31f Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 8 Feb 2019 15:37:02 +0000 Subject: [PATCH] drm/i915: Defer removing fence register tracking to rpm wakeup Currently, we may simultaneously release the fence register from both fence_update() and i915_gem_restore_fences(). This is dangerous, so defer the bookkeeping entirely to i915_gem_restore_fences() when the device is asleep. Reported-by: Mika Kuoppala Signed-off-by: Chris Wilson Cc: Mika Kuoppala Reviewed-by: Mika Kuoppala Link: https://patchwork.freedesktop.org/patch/msgid/20190208153708.20023-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_gem_fence_reg.c | 62 ++++++++++++++++--------------- 1 file changed, 32 insertions(+), 30 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem_fence_reg.c b/drivers/gpu/drm/i915/i915_gem_fence_reg.c index e037e94..be89bd9 100644 --- a/drivers/gpu/drm/i915/i915_gem_fence_reg.c +++ b/drivers/gpu/drm/i915/i915_gem_fence_reg.c @@ -210,6 +210,7 @@ static int fence_update(struct drm_i915_fence_reg *fence, struct i915_vma *vma) { intel_wakeref_t wakeref; + struct i915_vma *old; int ret; if (vma) { @@ -229,49 +230,55 @@ static int fence_update(struct drm_i915_fence_reg *fence, return ret; } - if (fence->vma) { - struct i915_vma *old = fence->vma; - + old = xchg(&fence->vma, NULL); + if (old) { ret = i915_active_request_retire(&old->last_fence, &old->obj->base.dev->struct_mutex); - if (ret) + if (ret) { + fence->vma = old; return ret; + } i915_vma_flush_writes(old); - } - if (fence->vma && fence->vma != vma) { - /* Ensure that all userspace CPU access is completed before + /* + * Ensure that all userspace CPU access is completed before * stealing the fence. */ - GEM_BUG_ON(fence->vma->fence != fence); - i915_vma_revoke_mmap(fence->vma); - - fence->vma->fence = NULL; - fence->vma = NULL; + if (old != vma) { + GEM_BUG_ON(old->fence != fence); + i915_vma_revoke_mmap(old); + old->fence = NULL; + } list_move(&fence->link, &fence->i915->mm.fence_list); } - /* We only need to update the register itself if the device is awake. + /* + * We only need to update the register itself if the device is awake. * If the device is currently powered down, we will defer the write * to the runtime resume, see i915_gem_restore_fences(). + * + * This only works for removing the fence register, on acquisition + * the caller must hold the rpm wakeref. The fence register must + * be cleared before we can use any other fences to ensure that + * the new fences do not overlap the elided clears, confusing HW. */ wakeref = intel_runtime_pm_get_if_in_use(fence->i915); - if (wakeref) { - fence_write(fence, vma); - intel_runtime_pm_put(fence->i915, wakeref); + if (!wakeref) { + GEM_BUG_ON(vma); + return 0; } - if (vma) { - if (fence->vma != vma) { - vma->fence = fence; - fence->vma = vma; - } + fence_write(fence, vma); + fence->vma = vma; + if (vma) { + vma->fence = fence; list_move_tail(&fence->link, &fence->i915->mm.fence_list); } + intel_runtime_pm_put(fence->i915, wakeref); return 0; } @@ -473,9 +480,10 @@ void i915_gem_restore_fences(struct drm_i915_private *dev_priv) { int i; + rcu_read_lock(); /* keep obj alive as we dereference */ for (i = 0; i < dev_priv->num_fence_regs; i++) { struct drm_i915_fence_reg *reg = &dev_priv->fence_regs[i]; - struct i915_vma *vma = reg->vma; + struct i915_vma *vma = READ_ONCE(reg->vma); GEM_BUG_ON(vma && vma->fence != reg); @@ -483,18 +491,12 @@ void i915_gem_restore_fences(struct drm_i915_private *dev_priv) * Commit delayed tiling changes if we have an object still * attached to the fence, otherwise just clear the fence. */ - if (vma && !i915_gem_object_is_tiled(vma->obj)) { - GEM_BUG_ON(!reg->dirty); - GEM_BUG_ON(i915_vma_has_userfault(vma)); - - list_move(®->link, &dev_priv->mm.fence_list); - vma->fence = NULL; + if (vma && !i915_gem_object_is_tiled(vma->obj)) vma = NULL; - } fence_write(reg, vma); - reg->vma = vma; } + rcu_read_unlock(); } /** -- 2.7.4