drm/i915: Identify active requests

To allow requests to forgo a common execution timeline, one question we
need to be able to answer is "is this request running?". To track
whether a request has started on HW, we can emit a breadcrumb at the
beginning of the request and check its timeline's HWSP to see if the
breadcrumb has advanced past the start of this request. (This is in
contrast to the global timeline where we need only ask if we are on the
global timeline and if the timeline has advanced past the end of the
previous request.)

There is still confusion from a preempted request, which has already
started but relinquished the HW to a high priority request. For the
common case, this discrepancy should be negligible. However, for
identification of hung requests, knowing which one was running at the
time of the hang will be much more important.

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/20190129185452.20989-2-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9c499edb4c138eeabffb9cac8306b617ffb86968..d92e7ab0005e515d8fe6bc6bdbf824a0290f8dc1 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2871,6 +2871,14 @@ i915_gem_object_pwrite_gtt(struct drm_i915_gem_object *obj,
        return 0;
 }
 
+static bool match_ring(struct i915_request *rq)
+{
+       struct drm_i915_private *dev_priv = rq->i915;
+       u32 ring = I915_READ(RING_START(rq->engine->mmio_base));
+
+       return ring == i915_ggtt_offset(rq->ring->vma);
+}
+
 struct i915_request *
 i915_gem_find_active_request(struct intel_engine_cs *engine)
 {
@@ -2893,6 +2901,13 @@ i915_gem_find_active_request(struct intel_engine_cs *engine)
                if (i915_request_completed(request))
                        continue;
 
+               if (!i915_request_started(request))
+                       break;
+
+               /* More than one preemptible request may match! */
+               if (!match_ring(request))
+                       break;
+
                active = request;
                break;
        }

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index f250109e1f66300714a72c65ed637293a92a7888..8eedf7cac4938f1444b2aa32e346182a038ec9a6 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1976,6 +1976,18 @@ static int eb_submit(struct i915_execbuffer *eb)
                        return err;
        }
 
+       /*
+        * After we completed waiting for other engines (using HW semaphores)
+        * then we can signal that this request/batch is ready to run. This
+        * allows us to determine if the batch is still waiting on the GPU
+        * or actually running by checking the breadcrumb.
+        */
+       if (eb->engine->emit_init_breadcrumb) {
+               err = eb->engine->emit_init_breadcrumb(eb->request);
+               if (err)
+                       return err;
+       }
+
        err = eb->engine->emit_bb_start(eb->request,
                                        eb->batch->node.start +
                                        eb->batch_start_offset,

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 4d58770e6a8c2bef437ab4a9a71091f46c5380d2..7db15b7b3de89ffddeb5c37f75704188dd0ba700 100644 (file)
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -333,7 +333,7 @@ void i915_request_retire_upto(struct i915_request *rq)
 
 static u32 timeline_get_seqno(struct i915_timeline *tl)
 {
-       return ++tl->seqno;
+       return tl->seqno += 1 + tl->has_initial_breadcrumb;
 }
 
 static void move_to_timeline(struct i915_request *request,
@@ -382,8 +382,8 @@ void __i915_request_submit(struct i915_request *request)
                intel_engine_enable_signaling(request, false);
        spin_unlock(&request->lock);
 
-       engine->emit_breadcrumb(request,
-                               request->ring->vaddr + request->postfix);
+       engine->emit_fini_breadcrumb(request,
+                                    request->ring->vaddr + request->postfix);
 
        /* Transfer from per-context onto the global per-engine timeline */
        move_to_timeline(request, &engine->timeline);
@@ -657,7 +657,7 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx)
         * around inside i915_request_add() there is sufficient space at
         * the beginning of the ring as well.
         */
-       rq->reserved_space = 2 * engine->emit_breadcrumb_dw * sizeof(u32);
+       rq->reserved_space = 2 * engine->emit_fini_breadcrumb_dw * sizeof(u32);
 
        /*
         * Record the position of the start of the request so that
@@ -908,7 +908,7 @@ void i915_request_add(struct i915_request *request)
         * GPU processing the request, we never over-estimate the
         * position of the ring's HEAD.
         */
-       cs = intel_ring_begin(request, engine->emit_breadcrumb_dw);
+       cs = intel_ring_begin(request, engine->emit_fini_breadcrumb_dw);
        GEM_BUG_ON(IS_ERR(cs));
        request->postfix = intel_ring_offset(request, cs);
 

diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
index 96c586d6ff4d8275a00d2f3aa6367b5b194493bf..340d6216791ca2c372739426c993f74be61a0025 100644 (file)
--- a/drivers/gpu/drm/i915/i915_request.h
+++ b/drivers/gpu/drm/i915/i915_request.h
@@ -344,6 +344,7 @@ static inline bool i915_request_started(const struct i915_request *rq)
        if (i915_request_signaled(rq))
                return true;
 
+       /* Remember: started but may have since been preempted! */
        return i915_seqno_passed(hwsp_seqno(rq), rq->fence.seqno - 1);
 }
 

diff --git a/drivers/gpu/drm/i915/i915_timeline.c b/drivers/gpu/drm/i915/i915_timeline.c
index 79838d89bdb9405afe60f6eb716fa3bc21804e11..5ea3af393ffe8a33b03c9199371aadea1b50305c 100644 (file)
--- a/drivers/gpu/drm/i915/i915_timeline.c
+++ b/drivers/gpu/drm/i915/i915_timeline.c
@@ -135,6 +135,7 @@ int i915_timeline_init(struct drm_i915_private *i915,
        timeline->i915 = i915;
        timeline->name = name;
        timeline->pin_count = 0;
+       timeline->has_initial_breadcrumb = !hwsp;
 
        timeline->hwsp_offset = I915_GEM_HWS_SEQNO_ADDR;
        if (!hwsp) {

diff --git a/drivers/gpu/drm/i915/i915_timeline.h b/drivers/gpu/drm/i915/i915_timeline.h
index ab736e2e5707713264af0ae5d3e2c0da9ee5f13d..8caeb66d1cd554e94a10da9d2ba3cc0c6bd529ad 100644 (file)
--- a/drivers/gpu/drm/i915/i915_timeline.h
+++ b/drivers/gpu/drm/i915/i915_timeline.h
@@ -48,6 +48,8 @@ struct i915_timeline {
        struct i915_vma *hwsp_ggtt;
        u32 hwsp_offset;
 
+       bool has_initial_breadcrumb;
+
        /**
         * List of breadcrumbs associated with GPU requests currently
         * outstanding.

diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index ead9c4371fe1e639b73a2388df18284711ffea12..8dca76f6315d958f654c24d85aca411ef9545fe7 100644 (file)
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -664,7 +664,7 @@ static int measure_breadcrumb_dw(struct intel_engine_cs *engine)
        if (dw < 0)
                goto out_timeline;
 
-       dw = engine->emit_breadcrumb(&frame->rq, frame->cs) - frame->cs;
+       dw = engine->emit_fini_breadcrumb(&frame->rq, frame->cs) - frame->cs;
 
        i915_timeline_unpin(&frame->timeline);
 
@@ -725,7 +725,7 @@ int intel_engine_init_common(struct intel_engine_cs *engine)
        if (ret < 0)
                goto err_breadcrumbs;
 
-       engine->emit_breadcrumb_dw = ret;
+       engine->emit_fini_breadcrumb_dw = ret;
 
        return 0;
 
@@ -1297,7 +1297,9 @@ static void print_request(struct drm_printer *m,
        drm_printf(m, "%s%x%s [%llx:%llx]%s @ %dms: %s\n",
                   prefix,
                   rq->global_seqno,
-                  i915_request_completed(rq) ? "!" : "",
+                  i915_request_completed(rq) ? "!" :
+                  i915_request_started(rq) ? "*" :
+                  "",
                   rq->fence.context, rq->fence.seqno,
                   buf,
                   jiffies_to_msecs(jiffies - rq->emitted_jiffies),

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index fdbb3fe8eac9e6109b201ecf7d2be72ee6c72cf4..5db16dd8e84499fcb5cdf0dc38692a12e86b39aa 100644 (file)
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -624,7 +624,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
                 * WaIdleLiteRestore:bdw,skl
                 * Apply the wa NOOPs to prevent
                 * ring:HEAD == rq:TAIL as we resubmit the
-                * request. See gen8_emit_breadcrumb() for
+                * request. See gen8_emit_fini_breadcrumb() for
                 * where we prepare the padding after the
                 * end of the request.
                 */
@@ -1283,6 +1283,34 @@ execlists_context_pin(struct intel_engine_cs *engine,
        return __execlists_context_pin(engine, ctx, ce);
 }
 
+static int gen8_emit_init_breadcrumb(struct i915_request *rq)
+{
+       u32 *cs;
+
+       GEM_BUG_ON(!rq->timeline->has_initial_breadcrumb);
+
+       cs = intel_ring_begin(rq, 6);
+       if (IS_ERR(cs))
+               return PTR_ERR(cs);
+
+       /*
+        * Check if we have been preempted before we even get started.
+        *
+        * After this point i915_request_started() reports true, even if
+        * we get preempted and so are no longer running.
+        */
+       *cs++ = MI_ARB_CHECK;
+       *cs++ = MI_NOOP;
+
+       *cs++ = MI_STORE_DWORD_IMM_GEN4 | MI_USE_GGTT;
+       *cs++ = rq->timeline->hwsp_offset;
+       *cs++ = 0;
+       *cs++ = rq->fence.seqno - 1;
+
+       intel_ring_advance(rq, cs);
+       return 0;
+}
+
 static int emit_pdps(struct i915_request *rq)
 {
        const struct intel_engine_cs * const engine = rq->engine;
@@ -2039,7 +2067,7 @@ static u32 *gen8_emit_wa_tail(struct i915_request *request, u32 *cs)
        return cs;
 }
 
-static u32 *gen8_emit_breadcrumb(struct i915_request *request, u32 *cs)
+static u32 *gen8_emit_fini_breadcrumb(struct i915_request *request, u32 *cs)
 {
        /* w/a: bit 5 needs to be zero for MI_FLUSH_DW address. */
        BUILD_BUG_ON(I915_GEM_HWS_INDEX_ADDR & (1 << 5));
@@ -2061,7 +2089,7 @@ static u32 *gen8_emit_breadcrumb(struct i915_request *request, u32 *cs)
        return gen8_emit_wa_tail(request, cs);
 }
 
-static u32 *gen8_emit_breadcrumb_rcs(struct i915_request *request, u32 *cs)
+static u32 *gen8_emit_fini_breadcrumb_rcs(struct i915_request *request, u32 *cs)
 {
        cs = gen8_emit_ggtt_write_rcs(cs,
                                      request->fence.seqno,
@@ -2176,7 +2204,8 @@ logical_ring_default_vfuncs(struct intel_engine_cs *engine)
        engine->request_alloc = execlists_request_alloc;
 
        engine->emit_flush = gen8_emit_flush;
-       engine->emit_breadcrumb = gen8_emit_breadcrumb;
+       engine->emit_init_breadcrumb = gen8_emit_init_breadcrumb;
+       engine->emit_fini_breadcrumb = gen8_emit_fini_breadcrumb;
 
        engine->set_default_submission = intel_execlists_set_default_submission;
 
@@ -2289,7 +2318,7 @@ int logical_render_ring_init(struct intel_engine_cs *engine)
        /* Override some for render ring. */
        engine->init_context = gen8_init_rcs_context;
        engine->emit_flush = gen8_emit_flush_render;
-       engine->emit_breadcrumb = gen8_emit_breadcrumb_rcs;
+       engine->emit_fini_breadcrumb = gen8_emit_fini_breadcrumb_rcs;
 
        ret = logical_ring_init(engine);
        if (ret)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index ee3719324e2dee13ea0110ee6d9fad5878e8144a..668ed67336a2a26bb44c035cdb40c20f1ca46f82 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1607,6 +1607,7 @@ static int intel_init_ring_buffer(struct intel_engine_cs *engine)
                err = PTR_ERR(timeline);
                goto err;
        }
+       GEM_BUG_ON(timeline->has_initial_breadcrumb);
 
        ring = intel_engine_create_ring(engine, timeline, 32 * PAGE_SIZE);
        i915_timeline_put(timeline);
@@ -1960,6 +1961,7 @@ static int ring_request_alloc(struct i915_request *request)
        int ret;
 
        GEM_BUG_ON(!request->hw_context->pin_count);
+       GEM_BUG_ON(request->timeline->has_initial_breadcrumb);
 
        /*
         * Flush enough space to reduce the likelihood of waiting after
@@ -2296,9 +2298,14 @@ static void intel_ring_default_vfuncs(struct drm_i915_private *dev_priv,
        engine->context_pin = intel_ring_context_pin;
        engine->request_alloc = ring_request_alloc;
 
-       engine->emit_breadcrumb = i9xx_emit_breadcrumb;
+       /*
+        * Using a global execution timeline; the previous final breadcrumb is
+        * equivalent to our next initial bread so we can elide
+        * engine->emit_init_breadcrumb().
+        */
+       engine->emit_fini_breadcrumb = i9xx_emit_breadcrumb;
        if (IS_GEN(dev_priv, 5))
-               engine->emit_breadcrumb = gen5_emit_breadcrumb;
+               engine->emit_fini_breadcrumb = gen5_emit_breadcrumb;
 
        engine->set_default_submission = i9xx_set_default_submission;
 
@@ -2327,11 +2334,11 @@ int intel_init_render_ring_buffer(struct intel_engine_cs *engine)
        if (INTEL_GEN(dev_priv) >= 7) {
                engine->init_context = intel_rcs_ctx_init;
                engine->emit_flush = gen7_render_ring_flush;
-               engine->emit_breadcrumb = gen7_rcs_emit_breadcrumb;
+               engine->emit_fini_breadcrumb = gen7_rcs_emit_breadcrumb;
        } else if (IS_GEN(dev_priv, 6)) {
                engine->init_context = intel_rcs_ctx_init;
                engine->emit_flush = gen6_render_ring_flush;
-               engine->emit_breadcrumb = gen6_rcs_emit_breadcrumb;
+               engine->emit_fini_breadcrumb = gen6_rcs_emit_breadcrumb;
        } else if (IS_GEN(dev_priv, 5)) {
                engine->emit_flush = gen4_render_ring_flush;
        } else {
@@ -2368,9 +2375,9 @@ int intel_init_bsd_ring_buffer(struct intel_engine_cs *engine)
                engine->irq_enable_mask = GT_BSD_USER_INTERRUPT;
 
                if (IS_GEN(dev_priv, 6))
-                       engine->emit_breadcrumb = gen6_xcs_emit_breadcrumb;
+                       engine->emit_fini_breadcrumb = gen6_xcs_emit_breadcrumb;
                else
-                       engine->emit_breadcrumb = gen7_xcs_emit_breadcrumb;
+                       engine->emit_fini_breadcrumb = gen7_xcs_emit_breadcrumb;
        } else {
                engine->emit_flush = bsd_ring_flush;
                if (IS_GEN(dev_priv, 5))
@@ -2394,9 +2401,9 @@ int intel_init_blt_ring_buffer(struct intel_engine_cs *engine)
        engine->irq_enable_mask = GT_BLT_USER_INTERRUPT;
 
        if (IS_GEN(dev_priv, 6))
-               engine->emit_breadcrumb = gen6_xcs_emit_breadcrumb;
+               engine->emit_fini_breadcrumb = gen6_xcs_emit_breadcrumb;
        else
-               engine->emit_breadcrumb = gen7_xcs_emit_breadcrumb;
+               engine->emit_fini_breadcrumb = gen7_xcs_emit_breadcrumb;
 
        return intel_init_ring_buffer(engine);
 }
@@ -2414,7 +2421,7 @@ int intel_init_vebox_ring_buffer(struct intel_engine_cs *engine)
        engine->irq_enable = hsw_vebox_irq_enable;
        engine->irq_disable = hsw_vebox_irq_disable;
 
-       engine->emit_breadcrumb = gen7_xcs_emit_breadcrumb;
+       engine->emit_fini_breadcrumb = gen7_xcs_emit_breadcrumb;
 
        return intel_init_ring_buffer(engine);
 }

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 2927b712b973080159c4f447bba7319f670b6e41..1f30ffb84936f8ae34121ded689a4e5fee8b8441 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -463,8 +463,10 @@ struct intel_engine_cs {
                                         unsigned int dispatch_flags);
 #define I915_DISPATCH_SECURE BIT(0)
 #define I915_DISPATCH_PINNED BIT(1)
-       u32             *(*emit_breadcrumb)(struct i915_request *rq, u32 *cs);
-       int             emit_breadcrumb_dw;
+       int              (*emit_init_breadcrumb)(struct i915_request *rq);
+       u32             *(*emit_fini_breadcrumb)(struct i915_request *rq,
+                                                u32 *cs);
+       unsigned int    emit_fini_breadcrumb_dw;
 
        /* Pass the request to the hardware queue (e.g. directly into
         * the legacy ringbuffer or to the end of an execlist).

diff --git a/drivers/gpu/drm/i915/selftests/mock_engine.c b/drivers/gpu/drm/i915/selftests/mock_engine.c
index 95e890d7f58b27e5bcc028bcd503001fa2ad2249..3b226ebc6bc4cd9e0bc92b5c553a911c67549fca 100644 (file)
--- a/drivers/gpu/drm/i915/selftests/mock_engine.c
+++ b/drivers/gpu/drm/i915/selftests/mock_engine.c
@@ -227,7 +227,7 @@ struct intel_engine_cs *mock_engine(struct drm_i915_private *i915,
        engine->base.context_pin = mock_context_pin;
        engine->base.request_alloc = mock_request_alloc;
        engine->base.emit_flush = mock_emit_flush;
-       engine->base.emit_breadcrumb = mock_emit_breadcrumb;
+       engine->base.emit_fini_breadcrumb = mock_emit_breadcrumb;
        engine->base.submit_request = mock_submit_request;
 
        if (i915_timeline_init(i915,