[Intel-gfx] [PATCH 05/13] drm/i915: Convert requests to use struct fence
Jesse Barnes
jbarnes at virtuousgeek.org
Mon Jan 4 09:20:44 PST 2016
On 12/17/2015 09:43 AM, Jesse Barnes wrote:
> On 12/11/2015 05:11 AM, John.C.Harrison at Intel.com wrote:
>> From: John Harrison <John.C.Harrison at Intel.com>
>>
>> There is a construct in the linux kernel called 'struct fence' that is
>> intended to keep track of work that is executed on hardware. I.e. it
>> solves the basic problem that the drivers 'struct
>> drm_i915_gem_request' is trying to address. The request structure does
>> quite a lot more than simply track the execution progress so is very
>> definitely still required. However, the basic completion status side
>> could be updated to use the ready made fence implementation and gain
>> all the advantages that provides.
>>
>> This patch makes the first step of integrating a struct fence into the
>> request. It replaces the explicit reference count with that of the
>> fence. It also replaces the 'is completed' test with the fence's
>> equivalent. Currently, that simply chains on to the original request
>> implementation. A future patch will improve this.
>>
>> v3: Updated after review comments by Tvrtko Ursulin. Added fence
>> context/seqno pair to the debugfs request info. Renamed fence 'driver
>> name' to just 'i915'. Removed BUG_ONs.
>>
>> For: VIZ-5190
>> Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
>> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>> ---
>> drivers/gpu/drm/i915/i915_debugfs.c | 5 +--
>> drivers/gpu/drm/i915/i915_drv.h | 45 +++++++++++++-------------
>> drivers/gpu/drm/i915/i915_gem.c | 56 ++++++++++++++++++++++++++++++---
>> drivers/gpu/drm/i915/intel_lrc.c | 1 +
>> drivers/gpu/drm/i915/intel_ringbuffer.c | 1 +
>> drivers/gpu/drm/i915/intel_ringbuffer.h | 3 ++
>> 6 files changed, 81 insertions(+), 30 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
>> index 7415606..5b31186 100644
>> --- a/drivers/gpu/drm/i915/i915_debugfs.c
>> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
>> @@ -709,11 +709,12 @@ static int i915_gem_request_info(struct seq_file *m, void *data)
>> task = NULL;
>> if (req->pid)
>> task = pid_task(req->pid, PIDTYPE_PID);
>> - seq_printf(m, " %x @ %d: %s [%d]\n",
>> + seq_printf(m, " %x @ %d: %s [%d], fence = %u.%u\n",
>> req->seqno,
>> (int) (jiffies - req->emitted_jiffies),
>> task ? task->comm : "<unknown>",
>> - task ? task->pid : -1);
>> + task ? task->pid : -1,
>> + req->fence.context, req->fence.seqno);
>> rcu_read_unlock();
>> }
>>
>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>> index 436149e..aa5cba7 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -51,6 +51,7 @@
>> #include <linux/kref.h>
>> #include <linux/pm_qos.h>
>> #include "intel_guc.h"
>> +#include <linux/fence.h>
>>
>> /* General customization:
>> */
>> @@ -2174,7 +2175,17 @@ void i915_gem_track_fb(struct drm_i915_gem_object *old,
>> * initial reference taken using kref_init
>> */
>> struct drm_i915_gem_request {
>> - struct kref ref;
>> + /**
>> + * Underlying object for implementing the signal/wait stuff.
>> + * NB: Never call fence_later() or return this fence object to user
>> + * land! Due to lazy allocation, scheduler re-ordering, pre-emption,
>> + * etc., there is no guarantee at all about the validity or
>> + * sequentiality of the fence's seqno! It is also 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.
>> + */
>> + struct fence fence;
>>
>> /** On Which ring this request was generated */
>> struct drm_i915_private *i915;
>> @@ -2251,7 +2262,13 @@ int i915_gem_request_alloc(struct intel_engine_cs *ring,
>> struct intel_context *ctx,
>> struct drm_i915_gem_request **req_out);
>> void i915_gem_request_cancel(struct drm_i915_gem_request *req);
>> -void i915_gem_request_free(struct kref *req_ref);
>> +
>> +static inline bool i915_gem_request_completed(struct drm_i915_gem_request *req,
>> + bool lazy_coherency)
>> +{
>> + return fence_is_signaled(&req->fence);
>> +}
>> +
>> int i915_gem_request_add_to_client(struct drm_i915_gem_request *req,
>> struct drm_file *file);
>>
>> @@ -2271,7 +2288,7 @@ static inline struct drm_i915_gem_request *
>> i915_gem_request_reference(struct drm_i915_gem_request *req)
>> {
>> if (req)
>> - kref_get(&req->ref);
>> + fence_get(&req->fence);
>> return req;
>> }
>>
>> @@ -2279,7 +2296,7 @@ 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);
>> + fence_put(&req->fence);
>> }
>>
>> static inline void
>> @@ -2291,7 +2308,7 @@ i915_gem_request_unreference__unlocked(struct drm_i915_gem_request *req)
>> return;
>>
>> dev = req->ring->dev;
>> - if (kref_put_mutex(&req->ref, i915_gem_request_free, &dev->struct_mutex))
>> + if (kref_put_mutex(&req->fence.refcount, fence_release, &dev->struct_mutex))
>> mutex_unlock(&dev->struct_mutex);
>> }
>>
>> @@ -2308,12 +2325,6 @@ static inline void i915_gem_request_assign(struct drm_i915_gem_request **pdst,
>> }
>>
>> /*
>> - * XXX: i915_gem_request_completed should be here but currently needs the
>> - * definition of i915_seqno_passed() which is below. It will be moved in
>> - * a later patch when the call to i915_seqno_passed() is obsoleted...
>> - */
>> -
>> -/*
>> * A command that requires special handling by the command parser.
>> */
>> struct drm_i915_cmd_descriptor {
>> @@ -2916,18 +2927,6 @@ i915_seqno_passed(uint32_t seq1, uint32_t seq2)
>> return (int32_t)(seq1 - seq2) >= 0;
>> }
>>
>> -static inline bool i915_gem_request_completed(struct drm_i915_gem_request *req,
>> - bool lazy_coherency)
>> -{
>> - u32 seqno;
>> -
>> - BUG_ON(req == NULL);
>> -
>> - seqno = req->ring->get_seqno(req->ring, lazy_coherency);
>> -
>> - return i915_seqno_passed(seqno, req->seqno);
>> -}
>> -
>> int __must_check i915_gem_get_seqno(struct drm_device *dev, u32 *seqno);
>> int __must_check i915_gem_set_seqno(struct drm_device *dev, u32 seqno);
>>
>> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
>> index e4056a3..a1b4dbd 100644
>> --- a/drivers/gpu/drm/i915/i915_gem.c
>> +++ b/drivers/gpu/drm/i915/i915_gem.c
>> @@ -2617,12 +2617,14 @@ static void i915_set_reset_status(struct drm_i915_private *dev_priv,
>> }
>> }
>>
>> -void i915_gem_request_free(struct kref *req_ref)
>> +static void i915_gem_request_free(struct fence *req_fence)
>> {
>> - struct drm_i915_gem_request *req = container_of(req_ref,
>> - typeof(*req), ref);
>> + struct drm_i915_gem_request *req = container_of(req_fence,
>> + typeof(*req), fence);
>> struct intel_context *ctx = req->ctx;
>>
>> + WARN_ON(!mutex_is_locked(&req->ring->dev->struct_mutex));
>> +
>> if (req->file_priv)
>> i915_gem_request_remove_from_client(req);
>>
>> @@ -2638,6 +2640,45 @@ void i915_gem_request_free(struct kref *req_ref)
>> kmem_cache_free(req->i915->requests, req);
>> }
>>
>> +static bool i915_gem_request_enable_signaling(struct fence *req_fence)
>> +{
>> + /* Interrupt driven fences are not implemented yet.*/
>> + WARN(true, "This should not be called!");
>> + return true;
>> +}
>> +
>> +static bool i915_gem_request_is_completed(struct fence *req_fence)
>> +{
>> + struct drm_i915_gem_request *req = container_of(req_fence,
>> + typeof(*req), fence);
>> + u32 seqno;
>> +
>> + seqno = req->ring->get_seqno(req->ring, false/*lazy_coherency*/);
>> +
>> + return i915_seqno_passed(seqno, req->seqno);
>> +}
>> +
>> +static const char *i915_gem_request_get_driver_name(struct fence *req_fence)
>> +{
>> + return "i915";
>> +}
>> +
>> +static const char *i915_gem_request_get_timeline_name(struct fence *req_fence)
>> +{
>> + struct drm_i915_gem_request *req = container_of(req_fence,
>> + typeof(*req), fence);
>> + return req->ring->name;
>> +}
>> +
>> +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,
>> + .get_driver_name = i915_gem_request_get_driver_name,
>> + .get_timeline_name = i915_gem_request_get_timeline_name,
>> +};
>> +
>> int i915_gem_request_alloc(struct intel_engine_cs *ring,
>> struct intel_context *ctx,
>> struct drm_i915_gem_request **req_out)
>> @@ -2659,7 +2700,6 @@ int i915_gem_request_alloc(struct intel_engine_cs *ring,
>> if (ret)
>> goto err;
>>
>> - kref_init(&req->ref);
>> req->i915 = dev_priv;
>> req->ring = ring;
>> req->ctx = ctx;
>> @@ -2674,6 +2714,8 @@ int i915_gem_request_alloc(struct intel_engine_cs *ring,
>> goto err;
>> }
>>
>> + fence_init(&req->fence, &i915_gem_request_fops, &ring->fence_lock, ring->fence_context, req->seqno);
>> +
>> /*
>> * Reserve space in the ring buffer for all the commands required to
>> * eventually emit this request. This is to guarantee that the
>> @@ -4723,7 +4765,7 @@ i915_gem_init_hw(struct drm_device *dev)
>> {
>> struct drm_i915_private *dev_priv = dev->dev_private;
>> struct intel_engine_cs *ring;
>> - int ret, i, j;
>> + int ret, i, j, fence_base;
>>
>> if (INTEL_INFO(dev)->gen < 6 && !intel_enable_gtt())
>> return -EIO;
>> @@ -4793,12 +4835,16 @@ i915_gem_init_hw(struct drm_device *dev)
>> if (ret)
>> goto out;
>>
>> + fence_base = fence_context_alloc(I915_NUM_RINGS);
>> +
>> /* Now it is safe to go back round and do everything else: */
>> for_each_ring(ring, dev_priv, i) {
>> struct drm_i915_gem_request *req;
>>
>> WARN_ON(!ring->default_context);
>>
>> + ring->fence_context = fence_base + i;
>> +
>> ret = i915_gem_request_alloc(ring, ring->default_context, &req);
>> if (ret) {
>> i915_gem_cleanup_ringbuffer(dev);
>> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
>> index 06180dc..b8c8f9b 100644
>> --- a/drivers/gpu/drm/i915/intel_lrc.c
>> +++ b/drivers/gpu/drm/i915/intel_lrc.c
>> @@ -1920,6 +1920,7 @@ static int logical_ring_init(struct drm_device *dev, struct intel_engine_cs *rin
>> ring->dev = dev;
>> INIT_LIST_HEAD(&ring->active_list);
>> INIT_LIST_HEAD(&ring->request_list);
>> + spin_lock_init(&ring->fence_lock);
>> i915_gem_batch_pool_init(dev, &ring->batch_pool);
>> init_waitqueue_head(&ring->irq_queue);
>>
>> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
>> index c9b081f..f4a6403 100644
>> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
>> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
>> @@ -2158,6 +2158,7 @@ static int intel_init_ring_buffer(struct drm_device *dev,
>> INIT_LIST_HEAD(&ring->request_list);
>> INIT_LIST_HEAD(&ring->execlist_queue);
>> INIT_LIST_HEAD(&ring->buffers);
>> + spin_lock_init(&ring->fence_lock);
>> i915_gem_batch_pool_init(dev, &ring->batch_pool);
>> memset(ring->semaphore.sync_seqno, 0, sizeof(ring->semaphore.sync_seqno));
>>
>> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
>> index 58b1976..4547645 100644
>> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
>> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
>> @@ -348,6 +348,9 @@ struct intel_engine_cs {
>> * to encode the command length in the header).
>> */
>> u32 (*get_cmd_length_mask)(u32 cmd_header);
>> +
>> + unsigned fence_context;
>> + spinlock_t fence_lock;
>> };
>>
>> bool intel_ring_initialized(struct intel_engine_cs *ring);
>>
>
> Chris has an equivalent patch that does a little more (interrupt driven waits, custom i915 wait function, etc). Can you review that instead assuming it's sufficient?
>
> http://cgit.freedesktop.org/~ickle/linux-2.6/commit/?h=breadcrumbs&id=f062e706740d87befb8e7cd7ea337f98f0b24f52
Ok given that Chris's stuff is more ambitious, and this has already been
out there a long time and seen a lot of review, I think we should go
ahead with this version first, and then rebase Chris's stuff on top.
So this one has my ack.
Jesse
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