-----Original Message-----
From: Intel-gfx [mailto:intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx] On Behalf
Of John.C.Harrison@xxxxxxxxx
Sent: Friday, November 14, 2014 12:19 PM
To: Intel-GFX@xxxxxxxxxxxxxxxxxxxxx
Subject: [PATCH v2 11/28] drm/i915: Add IRQ friendly request
deference facility
From: John Harrison <John.C.Harrison@xxxxxxxxx>
The next patches in the series convert some display related seqno usage to
request structure usage. However, the request dereference introduced
must be done from interrupt context. As the dereference potentially
involves freeing the request structure and thus calling lots of non-interrupt
friendly code, this poses a problem.
The solution is to add an IRQ friendly version of the dereference function. All
this does is to add the request structure to a 'delayed free' list and return.
The retire code, which is run periodically, then processes this list and does
the actual dereferencing of the request structures.
v2: Added a count to allow for multiple IRQ dereferences of the same
request at a time.
For: VIZ-4377
Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_drv.h | 7 +++++++
drivers/gpu/drm/i915/i915_gem.c | 33
+++++++++++++++++++++++++++++++
drivers/gpu/drm/i915/intel_lrc.c | 2 ++
drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++
drivers/gpu/drm/i915/intel_ringbuffer.h | 2 ++
5 files changed, 47 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_drv.h
b/drivers/gpu/drm/i915/i915_drv.h index 180b674..87cb355 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2019,6 +2019,10 @@ struct drm_i915_gem_request {
struct drm_i915_file_private *file_priv;
/** file_priv list entry for this request */
struct list_head client_list;
+
+ /** deferred free list for dereferencing from IRQ context */
+ struct list_head delay_free_list;
+ uint32_t delay_free_count;
};
void i915_gem_request_free(struct kref *req_ref); @@ -2044,9 +2048,12
@@ 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));
kref_put(&req->ref, i915_gem_request_free); }
+void i915_gem_request_unreference_irq(struct drm_i915_gem_request
+*req);
+
static inline void i915_gem_request_assign(struct drm_i915_gem_request
**pdst,
struct drm_i915_gem_request *src)
{ diff --git a/drivers/gpu/drm/i915/i915_gem.c
b/drivers/gpu/drm/i915/i915_gem.c index 60e5eec..8453bbd 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2722,6 +2722,19 @@ void i915_gem_reset(struct drm_device *dev)
i915_gem_restore_fences(dev);
}
+void i915_gem_request_unreference_irq(struct drm_i915_gem_request
*req)
+{
+ struct intel_engine_cs *ring = req->ring;
+ unsigned long flags;
+
+ /* Need to add the req to a deferred dereference list to be
processed
+ * outside of interrupt time */
+ spin_lock_irqsave(&ring->reqlist_lock, flags);
+ if (req->delay_free_count++ == 0)
+ list_add_tail(&req->delay_free_list, &ring-
delayed_free_list);
+ spin_unlock_irqrestore(&ring->reqlist_lock, flags); }
+
/**
* This function clears the request list as sequence numbers are passed.
*/
@@ -2796,6 +2809,25 @@ i915_gem_retire_requests_ring(struct
intel_engine_cs *ring)
ring->trace_irq_seqno = 0;
}
+ while (!list_empty(&ring->delayed_free_list)) {
+ struct drm_i915_gem_request *request;
+ unsigned long flags;
+ uint32_t count;
+
+ request = list_first_entry(&ring->delayed_free_list,
+ struct drm_i915_gem_request,
+ delay_free_list);
+
+ spin_lock_irqsave(&request->ring->reqlist_lock, flags);
+ list_del(&request->delay_free_list);
+ count = request->delay_free_count;
+ request->delay_free_count = 0;
+ spin_unlock_irqrestore(&request->ring->reqlist_lock, flags);
+
+ while (count-- > 0)
+ i915_gem_request_unreference(request);
+ }
+
WARN_ON(i915_verify_lists(ring->dev));
}
@@ -5055,6 +5087,7 @@ init_ring_lists(struct intel_engine_cs *ring) {
INIT_LIST_HEAD(&ring->active_list);
INIT_LIST_HEAD(&ring->request_list);
+ INIT_LIST_HEAD(&ring->delayed_free_list);
