drm/i915: Introduce i915_timeline.mutex

A simple mutex used for guarding the flow of requests in and out of the
timeline. In the short-term, it will be used only to guard the addition
of requests into the timeline, taken on alloc and released on commit so
that only one caller can construct a request into the timeline
(important as the seqno and ring pointers must be serialised). This will
be used by observers to ensure that the seqno/hwsp is stable. Later,
when we have reduced retiring to only operate on a single timeline at a
time, we can then use the mutex as the sole guard required for retiring.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190301110547.14758-2-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index c65f6c990fddc99194c6158c97c9be38974099dc..719d1a5ab08277feee274b3d784303bdb539c9b6 100644 (file)
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -563,6 +563,7 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx)
                return ERR_CAST(ce);
 
        reserve_gt(i915);
+       mutex_lock(&ce->ring->timeline->mutex);
 
        /* Move our oldest request to the slab-cache (if not in use!) */
        rq = list_first_entry(&ce->ring->request_list, typeof(*rq), ring_link);
@@ -688,6 +689,7 @@ err_unwind:
 
        kmem_cache_free(global.slab_requests, rq);
 err_unreserve:
+       mutex_unlock(&ce->ring->timeline->mutex);
        unreserve_gt(i915);
        intel_context_unpin(ce);
        return ERR_PTR(ret);
@@ -880,7 +882,7 @@ void i915_request_add(struct i915_request *request)
        GEM_TRACE("%s fence %llx:%lld\n",
                  engine->name, request->fence.context, request->fence.seqno);
 
-       lockdep_assert_held(&request->i915->drm.struct_mutex);
+       lockdep_assert_held(&request->timeline->mutex);
        trace_i915_request_add(request);
 
        /*
@@ -991,6 +993,8 @@ void i915_request_add(struct i915_request *request)
         */
        if (prev && i915_request_completed(prev))
                i915_request_retire_upto(prev);
+
+       mutex_unlock(&request->timeline->mutex);
 }
 
 static unsigned long local_clock_us(unsigned int *cpu)

diff --git a/drivers/gpu/drm/i915/i915_timeline.c b/drivers/gpu/drm/i915/i915_timeline.c
index b2202d2e58a26341ab57cdc0fc3c86247d653ac4..87a80558da28297c747a4a6214590be63cdb406e 100644 (file)
--- a/drivers/gpu/drm/i915/i915_timeline.c
+++ b/drivers/gpu/drm/i915/i915_timeline.c
@@ -162,6 +162,7 @@ int i915_timeline_init(struct drm_i915_private *i915,
        timeline->fence_context = dma_fence_context_alloc(1);
 
        spin_lock_init(&timeline->lock);
+       mutex_init(&timeline->mutex);
 
        INIT_ACTIVE_REQUEST(&timeline->barrier);
        INIT_ACTIVE_REQUEST(&timeline->last_request);

diff --git a/drivers/gpu/drm/i915/i915_timeline.h b/drivers/gpu/drm/i915/i915_timeline.h
index 7bec7d2e45bfa242d30d8a76f38b99ae44226903..36c3849f71082ed88c07539813ec74e742b67c7b 100644 (file)
--- a/drivers/gpu/drm/i915/i915_timeline.h
+++ b/drivers/gpu/drm/i915/i915_timeline.h
@@ -44,6 +44,8 @@ struct i915_timeline {
 #define TIMELINE_CLIENT 0 /* default subclass */
 #define TIMELINE_ENGINE 1
 
+       struct mutex mutex; /* protects the flow of requests */
+
        unsigned int pin_count;
        const u32 *hwsp_seqno;
        struct i915_vma *hwsp_ggtt;

diff --git a/drivers/gpu/drm/i915/selftests/i915_request.c b/drivers/gpu/drm/i915/selftests/i915_request.c
index 7da52e3d67af7b4cfc96d75d3e051950aa991bf4..7e1b65b8eb19fab2bb175793eefa65a4d6870d2b 100644 (file)
--- a/drivers/gpu/drm/i915/selftests/i915_request.c
+++ b/drivers/gpu/drm/i915/selftests/i915_request.c
@@ -141,14 +141,12 @@ static int igt_fence_wait(void *arg)
                err = -ENOMEM;
                goto out_locked;
        }
-       mutex_unlock(&i915->drm.struct_mutex); /* safe as we are single user */
 
        if (dma_fence_wait_timeout(&request->fence, false, T) != -ETIME) {
                pr_err("fence wait success before submit (expected timeout)!\n");
-               goto out_device;
+               goto out_locked;
        }
 
-       mutex_lock(&i915->drm.struct_mutex);
        i915_request_add(request);
        mutex_unlock(&i915->drm.struct_mutex);
 

diff --git a/drivers/gpu/drm/i915/selftests/mock_timeline.c b/drivers/gpu/drm/i915/selftests/mock_timeline.c
index d2de9ece211820e320c067832f346ad3c2cab180..416d85233263dbecf04229b3e6cf51558a9aed41 100644 (file)
--- a/drivers/gpu/drm/i915/selftests/mock_timeline.c
+++ b/drivers/gpu/drm/i915/selftests/mock_timeline.c
@@ -14,6 +14,7 @@ void mock_timeline_init(struct i915_timeline *timeline, u64 context)
        timeline->fence_context = context;
 
        spin_lock_init(&timeline->lock);
+       mutex_init(&timeline->mutex);
 
        INIT_ACTIVE_REQUEST(&timeline->barrier);
        INIT_ACTIVE_REQUEST(&timeline->last_request);