Re: [Intel-gfx] [RFC 6/9] drm/i915: Delay the freeing of requests until retire time
On 28/10/15 13:00, John Harrison wrote: On 23/07/2015 15:25, Tvrtko Ursulin wrote: Hi, On 07/17/2015 03:31 PM, john.c.harri...@intel.com wrote: From: John Harrison The request structure is reference counted. When the count reached zero, the request was immediately freed and all associated objects were unrefereced/unallocated. This meant that the driver mutex lock must be held at the point where the count reaches zero. This was fine while all references were held internally to the driver. However, the plan is to allow the underlying fence object (and hence the request itself) to be returned to other drivers and to userland. External users cannot be expected to acquire a driver private mutex lock. Rather than attempt to disentangle the request structure from the driver mutex lock, the decsion was to defer the free code until a later (safer) point. Hence this patch changes the unreference callback to merely move the request onto a delayed free list. The driver's retire worker thread will then process the list and actually call the free function on the requests. [new patch in series] For: VIZ-5190 Signed-off-by: John Harrison --- drivers/gpu/drm/i915/i915_drv.h | 22 +++--- drivers/gpu/drm/i915/i915_gem.c | 41 + drivers/gpu/drm/i915/intel_display.c| 2 +- drivers/gpu/drm/i915/intel_lrc.c| 2 ++ drivers/gpu/drm/i915/intel_pm.c | 2 +- drivers/gpu/drm/i915/intel_ringbuffer.c | 2 ++ drivers/gpu/drm/i915/intel_ringbuffer.h | 4 7 files changed, 50 insertions(+), 25 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 88a4746..61c3db2 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -2161,14 +2161,9 @@ void i915_gem_track_fb(struct drm_i915_gem_object *old, * initial reference taken using kref_init */ struct drm_i915_gem_request { -/** - * Underlying object for implementing the signal/wait stuff. - * NB: Never return this fence object to user land! It is unsafe to - * let anything outside of the i915 driver get hold of the fence - * object as the clean up when decrementing the reference count - * requires holding the driver mutex lock. - */ +/** Underlying object for implementing the signal/wait stuff. */ struct fence fence; +struct list_head delay_free_list; Maybe call this delay_free_link to continue the established convention. /** On Which ring this request was generated */ struct drm_i915_private *i915; @@ -2281,21 +2276,10 @@ i915_gem_request_reference(struct drm_i915_gem_request *req) static inline void i915_gem_request_unreference(struct drm_i915_gem_request *req) { - WARN_ON(!mutex_is_locked(&req->ring->dev->struct_mutex)); -fence_put(&req->fence); -} - -static inline void -i915_gem_request_unreference__unlocked(struct drm_i915_gem_request *req) -{ -struct drm_device *dev; - if (!req) return; -dev = req->ring->dev; -if (kref_put_mutex(&req->fence.refcount, fence_release, &dev->struct_mutex)) -mutex_unlock(&dev->struct_mutex); +fence_put(&req->fence); } static inline void i915_gem_request_assign(struct drm_i915_gem_request **pdst, diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index af79716..482835a 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2616,10 +2616,27 @@ static void i915_set_reset_status(struct drm_i915_private *dev_priv, } } -static void i915_gem_request_free(struct fence *req_fence) +static void i915_gem_request_release(struct fence *req_fence) { struct drm_i915_gem_request *req = container_of(req_fence, typeof(*req), fence); +struct intel_engine_cs *ring = req->ring; +struct drm_i915_private *dev_priv = to_i915(ring->dev); +unsigned long flags; + +/* + * Need to add the request to a deferred dereference list to be + * processed at a mutex lock safe time. + */ +spin_lock_irqsave(&ring->delayed_free_lock, flags); At the moment there is no request unreferencing from irq handlers right? Unless (or until) you plan to add that you could use simple spin_lock here. (And in the i915_gem_retire_requests_ring.) I don't believe there is an unreference at IRQ time at this precise moment. However, there certainly have been in various other iterations of the code (including one on the display side that has since disappeared due to changes by others completely unrelated to this work). So I would be nervous about not making it IRQ compatible. It seems like a bug waiting to happen. I think it is bad to take the cost of disabling interrupts for nothing. Once the unthinkable happens and driver is re-designed so that it is possible to unreference from IRQ context it could be added. @@ -2992,6 +3009,21 @@ i915_gem_retire_requests_ring(struct inte
Re: [Intel-gfx] [RFC 6/9] drm/i915: Delay the freeing of requests until retire time
On 23/07/2015 15:25, Tvrtko Ursulin wrote: Hi, On 07/17/2015 03:31 PM, john.c.harri...@intel.com wrote: From: John Harrison The request structure is reference counted. When the count reached zero, the request was immediately freed and all associated objects were unrefereced/unallocated. This meant that the driver mutex lock must be held at the point where the count reaches zero. This was fine while all references were held internally to the driver. However, the plan is to allow the underlying fence object (and hence the request itself) to be returned to other drivers and to userland. External users cannot be expected to acquire a driver private mutex lock. Rather than attempt to disentangle the request structure from the driver mutex lock, the decsion was to defer the free code until a later (safer) point. Hence this patch changes the unreference callback to merely move the request onto a delayed free list. The driver's retire worker thread will then process the list and actually call the free function on the requests. [new patch in series] For: VIZ-5190 Signed-off-by: John Harrison --- drivers/gpu/drm/i915/i915_drv.h | 22 +++--- drivers/gpu/drm/i915/i915_gem.c | 41 + drivers/gpu/drm/i915/intel_display.c| 2 +- drivers/gpu/drm/i915/intel_lrc.c| 2 ++ drivers/gpu/drm/i915/intel_pm.c | 2 +- drivers/gpu/drm/i915/intel_ringbuffer.c | 2 ++ drivers/gpu/drm/i915/intel_ringbuffer.h | 4 7 files changed, 50 insertions(+), 25 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 88a4746..61c3db2 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -2161,14 +2161,9 @@ void i915_gem_track_fb(struct drm_i915_gem_object *old, * initial reference taken using kref_init */ struct drm_i915_gem_request { -/** - * Underlying object for implementing the signal/wait stuff. - * NB: Never return this fence object to user land! It is unsafe to - * let anything outside of the i915 driver get hold of the fence - * object as the clean up when decrementing the reference count - * requires holding the driver mutex lock. - */ +/** Underlying object for implementing the signal/wait stuff. */ struct fence fence; +struct list_head delay_free_list; Maybe call this delay_free_link to continue the established convention. /** On Which ring this request was generated */ struct drm_i915_private *i915; @@ -2281,21 +2276,10 @@ i915_gem_request_reference(struct drm_i915_gem_request *req) static inline void i915_gem_request_unreference(struct drm_i915_gem_request *req) { - WARN_ON(!mutex_is_locked(&req->ring->dev->struct_mutex)); -fence_put(&req->fence); -} - -static inline void -i915_gem_request_unreference__unlocked(struct drm_i915_gem_request *req) -{ -struct drm_device *dev; - if (!req) return; -dev = req->ring->dev; -if (kref_put_mutex(&req->fence.refcount, fence_release, &dev->struct_mutex)) -mutex_unlock(&dev->struct_mutex); +fence_put(&req->fence); } static inline void i915_gem_request_assign(struct drm_i915_gem_request **pdst, diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index af79716..482835a 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2616,10 +2616,27 @@ static void i915_set_reset_status(struct drm_i915_private *dev_priv, } } -static void i915_gem_request_free(struct fence *req_fence) +static void i915_gem_request_release(struct fence *req_fence) { struct drm_i915_gem_request *req = container_of(req_fence, typeof(*req), fence); +struct intel_engine_cs *ring = req->ring; +struct drm_i915_private *dev_priv = to_i915(ring->dev); +unsigned long flags; + +/* + * Need to add the request to a deferred dereference list to be + * processed at a mutex lock safe time. + */ +spin_lock_irqsave(&ring->delayed_free_lock, flags); At the moment there is no request unreferencing from irq handlers right? Unless (or until) you plan to add that you could use simple spin_lock here. (And in the i915_gem_retire_requests_ring.) I don't believe there is an unreference at IRQ time at this precise moment. However, there certainly have been in various other iterations of the code (including one on the display side that has since disappeared due to changes by others completely unrelated to this work). So I would be nervous about not making it IRQ compatible. It seems like a bug waiting to happen. + list_add_tail(&req->delay_free_list, &ring->delayed_free_list); +spin_unlock_irqrestore(&ring->delayed_free_lock, flags); + +queue_delayed_work(dev_priv->wq, &dev_priv->mm.retire_work, 0); Have you decided to re-use the retire worker just for convenience of for some other
Re: [Intel-gfx] [RFC 6/9] drm/i915: Delay the freeing of requests until retire time
Hi, On 07/17/2015 03:31 PM, john.c.harri...@intel.com wrote: From: John Harrison The request structure is reference counted. When the count reached zero, the request was immediately freed and all associated objects were unrefereced/unallocated. This meant that the driver mutex lock must be held at the point where the count reaches zero. This was fine while all references were held internally to the driver. However, the plan is to allow the underlying fence object (and hence the request itself) to be returned to other drivers and to userland. External users cannot be expected to acquire a driver private mutex lock. Rather than attempt to disentangle the request structure from the driver mutex lock, the decsion was to defer the free code until a later (safer) point. Hence this patch changes the unreference callback to merely move the request onto a delayed free list. The driver's retire worker thread will then process the list and actually call the free function on the requests. [new patch in series] For: VIZ-5190 Signed-off-by: John Harrison --- drivers/gpu/drm/i915/i915_drv.h | 22 +++--- drivers/gpu/drm/i915/i915_gem.c | 41 + drivers/gpu/drm/i915/intel_display.c| 2 +- drivers/gpu/drm/i915/intel_lrc.c| 2 ++ drivers/gpu/drm/i915/intel_pm.c | 2 +- drivers/gpu/drm/i915/intel_ringbuffer.c | 2 ++ drivers/gpu/drm/i915/intel_ringbuffer.h | 4 7 files changed, 50 insertions(+), 25 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 88a4746..61c3db2 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -2161,14 +2161,9 @@ void i915_gem_track_fb(struct drm_i915_gem_object *old, * initial reference taken using kref_init */ struct drm_i915_gem_request { - /** -* Underlying object for implementing the signal/wait stuff. -* NB: Never return this fence object to user land! It is unsafe to -* let anything outside of the i915 driver get hold of the fence -* object as the clean up when decrementing the reference count -* requires holding the driver mutex lock. -*/ + /** Underlying object for implementing the signal/wait stuff. */ struct fence fence; + struct list_head delay_free_list; Maybe call this delay_free_link to continue the established convention. /** On Which ring this request was generated */ struct drm_i915_private *i915; @@ -2281,21 +2276,10 @@ i915_gem_request_reference(struct drm_i915_gem_request *req) static inline void i915_gem_request_unreference(struct drm_i915_gem_request *req) { - WARN_ON(!mutex_is_locked(&req->ring->dev->struct_mutex)); - fence_put(&req->fence); -} - -static inline void -i915_gem_request_unreference__unlocked(struct drm_i915_gem_request *req) -{ - struct drm_device *dev; - if (!req) return; - dev = req->ring->dev; - if (kref_put_mutex(&req->fence.refcount, fence_release, &dev->struct_mutex)) - mutex_unlock(&dev->struct_mutex); + fence_put(&req->fence); } static inline void i915_gem_request_assign(struct drm_i915_gem_request **pdst, diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index af79716..482835a 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2616,10 +2616,27 @@ static void i915_set_reset_status(struct drm_i915_private *dev_priv, } } -static void i915_gem_request_free(struct fence *req_fence) +static void i915_gem_request_release(struct fence *req_fence) { struct drm_i915_gem_request *req = container_of(req_fence, typeof(*req), fence); + struct intel_engine_cs *ring = req->ring; + struct drm_i915_private *dev_priv = to_i915(ring->dev); + unsigned long flags; + + /* +* Need to add the request to a deferred dereference list to be +* processed at a mutex lock safe time. +*/ + spin_lock_irqsave(&ring->delayed_free_lock, flags); At the moment there is no request unreferencing from irq handlers right? Unless (or until) you plan to add that you could use simple spin_lock here. (And in the i915_gem_retire_requests_ring.) + list_add_tail(&req->delay_free_list, &ring->delayed_free_list); + spin_unlock_irqrestore(&ring->delayed_free_lock, flags); + + queue_delayed_work(dev_priv->wq, &dev_priv->mm.retire_work, 0); Have you decided to re-use the retire worker just for convenience of for some other reason as well? I found it a bit unexpected and though dedicated request free worker would be cleaner, but I don't know, not a strong opinion. +} + +static void i915_gem_request_free(struct drm_i915_gem_request *req) +{ struct intel_context *ctx = req->ctx; BUG_ON(!mutex_is_locked(&
[Intel-gfx] [RFC 6/9] drm/i915: Delay the freeing of requests until retire time
From: John Harrison The request structure is reference counted. When the count reached zero, the request was immediately freed and all associated objects were unrefereced/unallocated. This meant that the driver mutex lock must be held at the point where the count reaches zero. This was fine while all references were held internally to the driver. However, the plan is to allow the underlying fence object (and hence the request itself) to be returned to other drivers and to userland. External users cannot be expected to acquire a driver private mutex lock. Rather than attempt to disentangle the request structure from the driver mutex lock, the decsion was to defer the free code until a later (safer) point. Hence this patch changes the unreference callback to merely move the request onto a delayed free list. The driver's retire worker thread will then process the list and actually call the free function on the requests. [new patch in series] For: VIZ-5190 Signed-off-by: John Harrison --- drivers/gpu/drm/i915/i915_drv.h | 22 +++--- drivers/gpu/drm/i915/i915_gem.c | 41 + drivers/gpu/drm/i915/intel_display.c| 2 +- drivers/gpu/drm/i915/intel_lrc.c| 2 ++ drivers/gpu/drm/i915/intel_pm.c | 2 +- drivers/gpu/drm/i915/intel_ringbuffer.c | 2 ++ drivers/gpu/drm/i915/intel_ringbuffer.h | 4 7 files changed, 50 insertions(+), 25 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 88a4746..61c3db2 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -2161,14 +2161,9 @@ void i915_gem_track_fb(struct drm_i915_gem_object *old, * initial reference taken using kref_init */ struct drm_i915_gem_request { - /** -* Underlying object for implementing the signal/wait stuff. -* NB: Never return this fence object to user land! It is unsafe to -* let anything outside of the i915 driver get hold of the fence -* object as the clean up when decrementing the reference count -* requires holding the driver mutex lock. -*/ + /** Underlying object for implementing the signal/wait stuff. */ struct fence fence; + struct list_head delay_free_list; /** On Which ring this request was generated */ struct drm_i915_private *i915; @@ -2281,21 +2276,10 @@ i915_gem_request_reference(struct drm_i915_gem_request *req) static inline void i915_gem_request_unreference(struct drm_i915_gem_request *req) { - WARN_ON(!mutex_is_locked(&req->ring->dev->struct_mutex)); - fence_put(&req->fence); -} - -static inline void -i915_gem_request_unreference__unlocked(struct drm_i915_gem_request *req) -{ - struct drm_device *dev; - if (!req) return; - dev = req->ring->dev; - if (kref_put_mutex(&req->fence.refcount, fence_release, &dev->struct_mutex)) - mutex_unlock(&dev->struct_mutex); + fence_put(&req->fence); } static inline void i915_gem_request_assign(struct drm_i915_gem_request **pdst, diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index af79716..482835a 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2616,10 +2616,27 @@ static void i915_set_reset_status(struct drm_i915_private *dev_priv, } } -static void i915_gem_request_free(struct fence *req_fence) +static void i915_gem_request_release(struct fence *req_fence) { struct drm_i915_gem_request *req = container_of(req_fence, typeof(*req), fence); + struct intel_engine_cs *ring = req->ring; + struct drm_i915_private *dev_priv = to_i915(ring->dev); + unsigned long flags; + + /* +* Need to add the request to a deferred dereference list to be +* processed at a mutex lock safe time. +*/ + spin_lock_irqsave(&ring->delayed_free_lock, flags); + list_add_tail(&req->delay_free_list, &ring->delayed_free_list); + spin_unlock_irqrestore(&ring->delayed_free_lock, flags); + + queue_delayed_work(dev_priv->wq, &dev_priv->mm.retire_work, 0); +} + +static void i915_gem_request_free(struct drm_i915_gem_request *req) +{ struct intel_context *ctx = req->ctx; BUG_ON(!mutex_is_locked(&req->ring->dev->struct_mutex)); @@ -2696,7 +2713,7 @@ static const struct fence_ops i915_gem_request_fops = { .enable_signaling = i915_gem_request_enable_signaling, .signaled = i915_gem_request_is_completed, .wait = fence_default_wait, - .release= i915_gem_request_free, + .release= i915_gem_request_release, .fence_value_str= i915_fence_value_str, .timeline_value_str = i915_fence_timeline_value_str, }; @@ -2992,6 +3009,21 @@ i915_gem_retire_requests_ri