On 06/07/2020 07:19, Chris Wilson wrote:
Our timeline lock is our defence against a concurrent execbuf
interrupting our request construction. we need hold it throughout or,
for example, a second thread may interject a relocation request in
between our own relocation request and execution in the ring.
A second, major benefit, is that it allows us to preserve a large chunk
of the ringbuffer for our exclusive use; which should virtually
eliminate the threat of hitting a wait_for_space during request
construction -- although we should have already dropped other
contentious locks at that point.
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
.../gpu/drm/i915/gem/i915_gem_execbuffer.c | 241 ++++++++++++------
.../i915/gem/selftests/i915_gem_execbuffer.c | 24 +-
2 files changed, 186 insertions(+), 79 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index dd15a799f9d6..e4d06db3f313 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -259,6 +259,8 @@ struct i915_execbuffer {
bool has_fence : 1;
bool needs_unfenced : 1;
+ struct intel_context *ce;
+
struct i915_vma *target;
struct i915_request *rq;
struct i915_vma *rq_vma;
@@ -639,6 +641,35 @@ static int eb_reserve_vma(const struct i915_execbuffer *eb,
return 0;
}
+static void retire_requests(struct intel_timeline *tl, struct i915_request *end)
+{
+ struct i915_request *rq, *rn;
+
+ list_for_each_entry_safe(rq, rn, &tl->requests, link)
+ if (rq == end || !i915_request_retire(rq))
+ break;
+}
+
+static int wait_for_timeline(struct intel_timeline *tl)
+{
+ do {
+ struct dma_fence *fence;
+ int err;
+
+ fence = i915_active_fence_get(&tl->last_request);
+ if (!fence)
+ return 0;
+
+ err = dma_fence_wait(fence, true);
+ dma_fence_put(fence);
+ if (err)
+ return err;
+
+ /* Retiring may trigger a barrier, requiring an extra pass */
+ retire_requests(tl, NULL);
+ } while (1);
+}
+
static int eb_reserve(struct i915_execbuffer *eb)
{
const unsigned int count = eb->buffer_count;
@@ -646,7 +677,6 @@ static int eb_reserve(struct i915_execbuffer *eb)
struct list_head last;
struct eb_vma *ev;
unsigned int i, pass;
- int err = 0;
/*
* Attempt to pin all of the buffers into the GTT.
@@ -662,18 +692,22 @@ static int eb_reserve(struct i915_execbuffer *eb)
* room for the earlier objects *unless* we need to defragment.
*/
- if (mutex_lock_interruptible(&eb->i915->drm.struct_mutex))
- return -EINTR;
-
pass = 0;
do {
+ int err = 0;
+
+ if (mutex_lock_interruptible(&eb->i915->drm.struct_mutex))
+ return -EINTR;
Recently you explained to me why we still use struct mutex here so
maybe, while moving the code, document that in a comment.
+
list_for_each_entry(ev, &eb->unbound, bind_link) {
err = eb_reserve_vma(eb, ev, pin_flags);
if (err)
break;
}
- if (!(err == -ENOSPC || err == -EAGAIN))
- break;
+ if (!(err == -ENOSPC || err == -EAGAIN)) {
+ mutex_unlock(&eb->i915->drm.struct_mutex);
+ return err;
+ }
/* Resort *all* the objects into priority order */
INIT_LIST_HEAD(&eb->unbound);
@@ -702,11 +736,10 @@ static int eb_reserve(struct i915_execbuffer *eb)
list_add_tail(&ev->bind_link, &last);
}
list_splice_tail(&last, &eb->unbound);
+ mutex_unlock(&eb->i915->drm.struct_mutex);
if (err == -EAGAIN) {
- mutex_unlock(&eb->i915->drm.struct_mutex);
flush_workqueue(eb->i915->mm.userptr_wq);
- mutex_lock(&eb->i915->drm.struct_mutex);
continue;
}
@@ -715,25 +748,23 @@ static int eb_reserve(struct i915_execbuffer *eb)
break;
case 1:
- /* Too fragmented, unbind everything and retry */
- mutex_lock(&eb->context->vm->mutex);
- err = i915_gem_evict_vm(eb->context->vm);
- mutex_unlock(&eb->context->vm->mutex);
+ /*
+ * Too fragmented, retire everything on the timeline
+ * and so make it all [contexts included] available to
+ * evict.
+ */
+ err = wait_for_timeline(eb->context->timeline);
if (err)
- goto unlock;
+ return err;
+
break;
default:
- err = -ENOSPC;
- goto unlock;
+ return -ENOSPC;
}
pin_flags = PIN_USER;
} while (1);
-
-unlock:
- mutex_unlock(&eb->i915->drm.struct_mutex);
- return err;
}
static unsigned int eb_batch_index(const struct i915_execbuffer *eb)
@@ -1007,13 +1038,44 @@ static int reloc_gpu_chain(struct reloc_cache *cache)
return err;
}
+static struct i915_request *
+nested_request_create(struct intel_context *ce)
+{
+ struct i915_request *rq;
+
+ /* XXX This only works once; replace with shared timeline */
Once as in attempt to use the same local intel_context from another eb
would upset lockdep? It's not a problem I think.
+ mutex_lock_nested(&ce->timeline->mutex, SINGLE_DEPTH_NESTING);
+ intel_context_enter(ce);
+
+ rq = __i915_request_create(ce, GFP_KERNEL);
+
+ intel_context_exit(ce);
+ if (IS_ERR(rq))
+ mutex_unlock(&ce->timeline->mutex);
+
+ return rq;
+}
+
+static void __i915_request_add(struct i915_request *rq,
+ struct i915_sched_attr *attr)
+{
+ struct intel_timeline * const tl = i915_request_timeline(rq);
+
+ lockdep_assert_held(&tl->mutex);
+ lockdep_unpin_lock(&tl->mutex, rq->cookie);
+
+ __i915_request_commit(rq);
+ __i915_request_queue(rq, attr);
+}
+
static unsigned int reloc_bb_flags(const struct reloc_cache *cache)
{
return cache->gen > 5 ? 0 : I915_DISPATCH_SECURE;
}
-static int reloc_gpu_flush(struct reloc_cache *cache)
+static int reloc_gpu_flush(struct i915_execbuffer *eb)
{
+ struct reloc_cache *cache = &eb->reloc_cache;
struct i915_request *rq;
int err;
@@ -1044,7 +1106,9 @@ static int reloc_gpu_flush(struct reloc_cache *cache)
i915_request_set_error_once(rq, err);
intel_gt_chipset_flush(rq->engine->gt);
- i915_request_add(rq);
+ __i915_request_add(rq, &eb->gem_context->sched);
+ if (i915_request_timeline(rq) != eb->context->timeline)
+ mutex_unlock(&i915_request_timeline(rq)->mutex);
return err;
}
@@ -1103,27 +1167,15 @@ static int __reloc_gpu_alloc(struct i915_execbuffer *eb,
if (err)
goto err_unmap;
- if (engine == eb->context->engine) {
- rq = i915_request_create(eb->context);
- } else {
- struct intel_context *ce;
-
- ce = intel_context_create(engine);
- if (IS_ERR(ce)) {
- err = PTR_ERR(ce);
- goto err_unpin;
- }
-
- i915_vm_put(ce->vm);
- ce->vm = i915_vm_get(eb->context->vm);
-
- rq = intel_context_create_request(ce);
- intel_context_put(ce);
- }
+ if (cache->ce == eb->context)
+ rq = __i915_request_create(cache->ce, GFP_KERNEL);
+ else
+ rq = nested_request_create(cache->ce);
if (IS_ERR(rq)) {
err = PTR_ERR(rq);
goto err_unpin;
}
+ rq->cookie = lockdep_pin_lock(&i915_request_timeline(rq)->mutex);
err = intel_gt_buffer_pool_mark_active(pool, rq);
if (err)
@@ -1151,7 +1203,9 @@ static int __reloc_gpu_alloc(struct i915_execbuffer *eb,
skip_request:
i915_request_set_error_once(rq, err);
err_request:
- i915_request_add(rq);
+ __i915_request_add(rq, &eb->gem_context->sched);
+ if (i915_request_timeline(rq) != eb->context->timeline)
+ mutex_unlock(&i915_request_timeline(rq)->mutex);
err_unpin:
i915_vma_unpin(batch);
err_unmap:
@@ -1161,11 +1215,6 @@ static int __reloc_gpu_alloc(struct i915_execbuffer *eb,
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);
-}
-
static u32 *reloc_gpu(struct i915_execbuffer *eb,
struct i915_vma *vma,
unsigned int len)
@@ -1177,12 +1226,6 @@ static u32 *reloc_gpu(struct i915_execbuffer *eb,
if (unlikely(!cache->rq)) {
struct intel_engine_cs *engine = eb->engine;
- if (!reloc_can_use_engine(engine)) {
- engine = engine->gt->engine_class[COPY_ENGINE_CLASS][0];
- if (!engine)
- return ERR_PTR(-ENODEV);
- }
-
err = __reloc_gpu_alloc(eb, engine, len);
if (unlikely(err))
return ERR_PTR(err);
@@ -1513,7 +1556,7 @@ static int eb_relocate(struct i915_execbuffer *eb)
break;
}
- flush = reloc_gpu_flush(&eb->reloc_cache);
+ flush = reloc_gpu_flush(eb);
if (!err)
err = flush;
}
@@ -1737,21 +1780,17 @@ parser_mark_active(struct eb_parse_work *pw, struct
intel_timeline *tl)
{
int err;
- mutex_lock(&tl->mutex);
-
err = __parser_mark_active(pw->shadow, tl, &pw->base.dma);
if (err)
- goto unlock;
+ return err;
if (pw->trampoline) {
err = __parser_mark_active(pw->trampoline, tl, &pw->base.dma);
if (err)
- goto unlock;
+ return err;
}
-unlock:
- mutex_unlock(&tl->mutex);
- return err;
+ return 0;
}
static int eb_parse_pipeline(struct i915_execbuffer *eb,
@@ -2044,6 +2083,54 @@ static struct i915_request *eb_throttle(struct
intel_context *ce)
return i915_request_get(rq);
}
+static bool reloc_can_use_engine(const struct intel_engine_cs *engine)
+{
+ return engine->class != VIDEO_DECODE_CLASS || !IS_GEN(engine->i915, 6);
+}
+
+static int __eb_pin_reloc_engine(struct i915_execbuffer *eb)
+{
+ struct intel_engine_cs *engine = eb->engine;
+ struct intel_context *ce;
+ int err;
+
+ if (reloc_can_use_engine(engine)) {
+ eb->reloc_cache.ce = eb->context;
+ return 0;
+ }
+
+ engine = engine->gt->engine_class[COPY_ENGINE_CLASS][0];
+ if (!engine)
+ return -ENODEV;
+
+ ce = intel_context_create(engine);
+ if (IS_ERR(ce))
+ return PTR_ERR(ce);
+
+ /* Reuse eb->context->timeline with scheduler! */
+
+ i915_vm_put(ce->vm);
+ ce->vm = i915_vm_get(eb->context->vm);
+
+ err = intel_context_pin(ce);
+ if (err)
+ return err;
+
+ eb->reloc_cache.ce = ce;
+ return 0;
+}
+
+static void __eb_unpin_reloc_engine(struct i915_execbuffer *eb)
+{
+ struct intel_context *ce = eb->reloc_cache.ce;
+
+ if (ce == eb->context)
+ return;
+
+ intel_context_unpin(ce);
+ intel_context_put(ce);
+}
+
static int __eb_pin_engine(struct i915_execbuffer *eb, struct intel_context
*ce)
{
struct intel_timeline *tl;
@@ -2087,9 +2174,7 @@ static int __eb_pin_engine(struct i915_execbuffer *eb,
struct intel_context *ce)
intel_context_enter(ce);
rq = eb_throttle(ce);
- intel_context_timeline_unlock(tl);
-
- if (rq) {
+ while (rq) {
bool nonblock = eb->file->filp->f_flags & O_NONBLOCK;
long timeout;
@@ -2097,23 +2182,34 @@ static int __eb_pin_engine(struct i915_execbuffer *eb, struct intel_context *ce)
if (nonblock)
timeout = 0;
+ mutex_unlock(&tl->mutex);
"Don't drop the timeline lock during execbuf"? Is the "during execbuf"
actually a smaller subset
+
timeout = i915_request_wait(rq,
I915_WAIT_INTERRUPTIBLE,
timeout);
i915_request_put(rq);
+ mutex_lock(&tl->mutex);
+
if (timeout < 0) {
err = nonblock ? -EWOULDBLOCK : timeout;
goto err_exit;
}
+
+ retire_requests(tl, NULL);
+ rq = eb_throttle(ce);
Alternative to avoid two call sites to eb_throttle of
while (rq = eb_throttle(ce)) {
Or checkpatch does not like it?
}
eb->engine = ce->engine;
eb->context = ce;
+
+ err = __eb_pin_reloc_engine(eb);
+ if (err)
+ goto err_exit;
+
return 0;
err_exit:
- mutex_lock(&tl->mutex);
intel_context_exit(ce);
intel_context_timeline_unlock(tl);
err_unpin:
@@ -2124,11 +2220,11 @@ static int __eb_pin_engine(struct i915_execbuffer *eb,
struct intel_context *ce)
static void eb_unpin_engine(struct i915_execbuffer *eb)
{
struct intel_context *ce = eb->context;
- struct intel_timeline *tl = ce->timeline;
- mutex_lock(&tl->mutex);
+ __eb_unpin_reloc_engine(eb);
+
intel_context_exit(ce);
- mutex_unlock(&tl->mutex);
+ intel_context_timeline_unlock(ce->timeline);
intel_context_unpin(ce);
}
@@ -2330,15 +2426,6 @@ signal_fence_array(struct i915_execbuffer *eb,
}
}
-static void retire_requests(struct intel_timeline *tl, struct i915_request *end)
-{
- struct i915_request *rq, *rn;
-
- list_for_each_entry_safe(rq, rn, &tl->requests, link)
- if (rq == end || !i915_request_retire(rq))
- break;
-}
-
static void eb_request_add(struct i915_execbuffer *eb)
{
struct i915_request *rq = eb->request;
@@ -2367,8 +2454,6 @@ static void eb_request_add(struct i915_execbuffer *eb)
/* Try to clean up the client's timeline after submitting the request */
if (prev)
retire_requests(tl, prev);
-
- mutex_unlock(&tl->mutex);
}
static int
@@ -2455,6 +2540,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
err = eb_pin_engine(&eb, file, args);
if (unlikely(err))
goto err_context;
+ lockdep_assert_held(&eb.context->timeline->mutex);
err = eb_relocate(&eb);
if (err) {
@@ -2522,11 +2608,12 @@ i915_gem_do_execbuffer(struct drm_device *dev,
GEM_BUG_ON(eb.reloc_cache.rq);
/* Allocate a request for this batch buffer nice and early. */
- eb.request = i915_request_create(eb.context);
+ eb.request = __i915_request_create(eb.context, GFP_KERNEL);
if (IS_ERR(eb.request)) {
err = PTR_ERR(eb.request);
goto err_batch_unpin;
}
+ eb.request->cookie = lockdep_pin_lock(&eb.context->timeline->mutex);
if (in_fence) {
if (args->flags & I915_EXEC_FENCE_SUBMIT)
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 57c14d3340cd..992d46db1b33 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_execbuffer.c
@@ -7,6 +7,9 @@
#include "gt/intel_engine_pm.h"
#include "selftests/igt_flush_test.h"
+#include "selftests/mock_drm.h"
+
+#include "mock_context.h"
static u64 read_reloc(const u32 *map, int x, const u64 mask)
{
@@ -60,7 +63,7 @@ static int __igt_gpu_reloc(struct i915_execbuffer *eb,
GEM_BUG_ON(!eb->reloc_cache.rq);
rq = i915_request_get(eb->reloc_cache.rq);
- err = reloc_gpu_flush(&eb->reloc_cache);
+ err = reloc_gpu_flush(eb);
if (err)
goto put_rq;
GEM_BUG_ON(eb->reloc_cache.rq);
@@ -100,14 +103,22 @@ static int igt_gpu_reloc(void *arg)
{
struct i915_execbuffer eb;
struct drm_i915_gem_object *scratch;
+ struct file *file;
int err = 0;
u32 *map;
+ file = mock_file(arg);
+ if (IS_ERR(file))
+ return PTR_ERR(file);
+
eb.i915 = arg;
+ eb.gem_context = live_context(arg, file);
+ if (IS_ERR(eb.gem_context))
+ goto err_file;
scratch = i915_gem_object_create_internal(eb.i915, 4096);
if (IS_ERR(scratch))
- return PTR_ERR(scratch);
+ goto err_file;
map = i915_gem_object_pin_map(scratch, I915_MAP_WC);
if (IS_ERR(map)) {
@@ -130,8 +141,15 @@ static int igt_gpu_reloc(void *arg)
if (err)
goto err_put;
+ mutex_lock(&eb.context->timeline->mutex);
+ intel_context_enter(eb.context);
+ eb.reloc_cache.ce = eb.context;
+
err = __igt_gpu_reloc(&eb, scratch);
+ intel_context_exit(eb.context);
+ mutex_unlock(&eb.context->timeline->mutex);
+
intel_context_unpin(eb.context);
err_put:
intel_context_put(eb.context);
@@ -146,6 +164,8 @@ static int igt_gpu_reloc(void *arg)
err_scratch:
i915_gem_object_put(scratch);
+err_file:
+ fput(file);
return err;
}
Regards,
Tvrtko
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