Asynchronous waits and signaling form a traditional semaphore with all
the usual ordering problems with taking multiple locks. If we want to
add more than one wait on a shared resource by the GPU, we must ensure
that all the associated timelines are advanced atomically, ergo we must
lock all the timelines en masse.
Testcase: igt/gem_exec_reloc/basic-concurrent16
Fixes: 0e97fbb08055 ("drm/i915/gem: Use a single chained reloc batches for a
single execbuf")
References: https://gitlab.freedesktop.org/drm/intel/-/issues/1889
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
.../gpu/drm/i915/gem/i915_gem_execbuffer.c | 114 ++++++++++++------
.../i915/gem/selftests/i915_gem_execbuffer.c | 24 ++--
2 files changed, 93 insertions(+), 45 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 4c3461ab8a63..373d5eea7a5a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -259,7 +259,6 @@ struct i915_execbuffer {
bool has_fence : 1;
bool needs_unfenced : 1;
- struct i915_vma *target;
struct i915_request *rq;
struct i915_vma *rq_vma;
u32 *rq_cmd;
@@ -924,7 +923,6 @@ static void reloc_cache_init(struct reloc_cache *cache,
cache->has_fence = cache->gen < 4;
cache->needs_unfenced = INTEL_INFO(i915)->unfenced_needs_alignment;
cache->node.flags = 0;
- cache->target = NULL;
}
static inline void *unmask_page(unsigned long p)
@@ -1057,26 +1055,6 @@ static void reloc_gpu_flush(struct reloc_cache *cache)
i915_request_add(rq);
}
-static int reloc_move_to_gpu(struct i915_request *rq, struct i915_vma *vma)
-{
- struct drm_i915_gem_object *obj = vma->obj;
- int err;
-
- i915_vma_lock(vma);
-
- if (obj->cache_dirty & ~obj->cache_coherent)
- i915_gem_clflush_object(obj, 0);
- obj->write_domain = 0;
-
- err = i915_request_await_object(rq, vma->obj, true);
- if (err == 0)
- err = i915_vma_move_to_active(vma, rq, EXEC_OBJECT_WRITE);
-
- i915_vma_unlock(vma);
-
- return err;
-}
-
static int
__reloc_gpu_alloc(struct i915_execbuffer *eb, struct intel_engine_cs *engine)
{
@@ -1166,24 +1144,12 @@ __reloc_gpu_alloc(struct i915_execbuffer *eb, struct
intel_engine_cs *engine)
return err;
}
-static u32 *reloc_batch_grow(struct i915_execbuffer *eb,
- struct i915_vma *vma,
- unsigned int len)
+static u32 *reloc_batch_grow(struct i915_execbuffer *eb, unsigned int len)
{
struct reloc_cache *cache = &eb->reloc_cache;
u32 *cmd;
int err;
- if (vma != cache->target) {
- err = reloc_move_to_gpu(cache->rq, vma);
- if (unlikely(err)) {
- i915_request_set_error_once(cache->rq, err);
- return ERR_PTR(err);
- }
-
- cache->target = vma;
- }
-
if (unlikely(cache->rq_size + len >
PAGE_SIZE / sizeof(u32) - RELOC_TAIL)) {
err = reloc_gpu_chain(cache);
@@ -1229,7 +1195,7 @@ static int __reloc_entry_gpu(struct i915_execbuffer *eb,
else
len = 3;
- batch = reloc_batch_grow(eb, vma, len);
+ batch = reloc_batch_grow(eb, len);
if (IS_ERR(batch))
return PTR_ERR(batch);
@@ -1549,6 +1515,78 @@ static long eb_reloc_vma_validate(struct i915_execbuffer
*eb, struct eb_vma *ev)
return required;
}
+static int reloc_move_to_gpu(struct reloc_cache *cache, struct eb_vma *ev)
+{
+ struct i915_request *rq = cache->rq;
+ struct i915_vma *vma = ev->vma;
+ struct drm_i915_gem_object *obj = vma->obj;
+ int err;
+
+ if (obj->cache_dirty & ~obj->cache_coherent)
+ i915_gem_clflush_object(obj, 0);
+
+ obj->write_domain = I915_GEM_DOMAIN_RENDER;
+ obj->read_domains = I915_GEM_DOMAIN_RENDER;
+
+ err = i915_request_await_object(rq, obj, true);
+ if (err)
+ return err;
+
+ err = __i915_vma_move_to_active(vma, rq);
+ if (err)
+ return err;
+
+ dma_resv_add_excl_fence(vma->resv, &rq->fence);
+
+ return 0;
+}
+
+static int
+lock_relocs(struct i915_execbuffer *eb)
+{
+ struct ww_acquire_ctx acquire;
+ struct eb_vma *ev;
+ int err = 0;
+
+ ww_acquire_init(&acquire, &reservation_ww_class);
+
+ list_for_each_entry(ev, &eb->relocs, reloc_link) {
+ struct i915_vma *vma = ev->vma;
+
+ err = ww_mutex_lock_interruptible(&vma->resv->lock, &acquire);
+ if (err == -EDEADLK) {
+ struct eb_vma *unlock = ev, *en;
+
+ list_for_each_entry_safe_continue_reverse(unlock, en,
+ &eb->relocs,
+ reloc_link) {
+ ww_mutex_unlock(&unlock->vma->resv->lock);
+ list_move_tail(&unlock->reloc_link,
+ &eb->relocs);
+ }
+
+ GEM_BUG_ON(!list_is_first(&ev->reloc_link,
+ &eb->relocs));
+ err = ww_mutex_lock_slow_interruptible(&vma->resv->lock,
+ &acquire);
+ }
+ if (err)
+ break;
+ }
+
+ ww_acquire_done(&acquire);
+
+ list_for_each_entry_continue_reverse(ev, &eb->relocs, reloc_link) {
+ if (err == 0)
+ err = reloc_move_to_gpu(&eb->reloc_cache, ev);
+ ww_mutex_unlock(&ev->vma->resv->lock);
+ }
+
+ ww_acquire_fini(&acquire);
+
+ return err;
+}
+
static bool reloc_can_use_engine(const struct intel_engine_cs *engine)
{
return engine->class != VIDEO_DECODE_CLASS || !IS_GEN(engine->i915, 6);
@@ -1577,6 +1615,10 @@ static int reloc_gpu(struct i915_execbuffer *eb)
return err;
GEM_BUG_ON(!eb->reloc_cache.rq);
+ err = lock_relocs(eb);
+ if (err)
+ goto out;
+
err = reloc_gpu_emit(&eb->reloc_cache);
if (err)
goto out;
diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_execbuffer.c
b/drivers/gpu/drm/i915/gem/selftests/i915_gem_execbuffer.c
index faed6480a792..4f10b51f9a7e 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_execbuffer.c
@@ -24,15 +24,15 @@ static int __igt_gpu_reloc(struct i915_execbuffer *eb,
GENMASK_ULL(eb->reloc_cache.use_64bit_reloc ? 63 : 31, 0);
const u32 *map = page_mask_bits(obj->mm.mapping);
struct i915_request *rq;
- struct i915_vma *vma;
+ struct eb_vma ev;
int err;
int i;
- vma = i915_vma_instance(obj, eb->context->vm, NULL);
- if (IS_ERR(vma))
- return PTR_ERR(vma);
+ ev.vma = i915_vma_instance(obj, eb->context->vm, NULL);
+ if (IS_ERR(ev.vma))
+ return PTR_ERR(ev.vma);
- err = i915_vma_pin(vma, 0, 0, PIN_USER | PIN_HIGH);
+ err = i915_vma_pin(ev.vma, 0, 0, PIN_USER | PIN_HIGH);
if (err)
return err;
@@ -40,17 +40,22 @@ static int __igt_gpu_reloc(struct i915_execbuffer *eb,
if (err)
goto unpin_vma;
+ list_add(&ev.reloc_link, &eb->relocs);
+ err = lock_relocs(eb);
+ if (err)
+ goto unpin_vma;
+
err = reloc_gpu_emit(&eb->reloc_cache);
if (err)
goto unpin_vma;
/* 8-Byte aligned */
- err = __reloc_entry_gpu(eb, vma, offsets[0] * sizeof(u32), 0);
+ err = __reloc_entry_gpu(eb, ev.vma, offsets[0] * sizeof(u32), 0);
if (err)
goto unpin_vma;
/* !8-Byte aligned */
- err = __reloc_entry_gpu(eb, vma, offsets[1] * sizeof(u32), 1);
+ err = __reloc_entry_gpu(eb, ev.vma, offsets[1] * sizeof(u32), 1);
if (err)
goto unpin_vma;
@@ -62,7 +67,7 @@ static int __igt_gpu_reloc(struct i915_execbuffer *eb,
eb->reloc_cache.rq_size += i;
/* Force batch chaining */
- err = __reloc_entry_gpu(eb, vma, offsets[2] * sizeof(u32), 2);
+ err = __reloc_entry_gpu(eb, ev.vma, offsets[2] * sizeof(u32), 2);
if (err)
goto unpin_vma;
@@ -97,7 +102,7 @@ static int __igt_gpu_reloc(struct i915_execbuffer *eb,
put_rq:
i915_request_put(rq);
unpin_vma:
- i915_vma_unpin(vma);
+ i915_vma_unpin(ev.vma);
return err;
}
@@ -121,6 +126,7 @@ static int igt_gpu_reloc(void *arg)
}
for_each_uabi_engine(eb.engine, eb.i915) {
+ INIT_LIST_HEAD(&eb.relocs);
reloc_cache_init(&eb.reloc_cache, eb.i915);
memset(map, POISON_INUSE, 4096);
--
2.20.1
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