Commit d8af05ff authored by Chris Wilson's avatar Chris Wilson

drm/i915: Allow sharing the idle-barrier from other kernel requests

By placing our idle-barriers in the i915_active fence tree, we expose
those for reuse by other components that are issuing requests along the
kernel_context. Reusing the proto-barrier active_node is perfectly fine
as the new request implies a context-switch, and so an opportune point
to run the idle-barrier. However, the proto-barrier is not equivalent
to a normal active_node and care must be taken to avoid dereferencing the
ERR_PTR used as its request marker.

v2: Comment the more egregious cheek
v3: A glossary!
Reported-by: default avatarLionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: ce476c80 ("drm/i915: Keep contexts pinned until after the next kernel context switch")
Fixes: a9877da2 ("drm/i915/oa: Reconfigure contexts on the fly")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190802100015.1281-1-chris@chris-wilson.co.uk
parent 576f0586
......@@ -162,23 +162,41 @@ static int __intel_context_active(struct i915_active *active)
if (err)
goto err_ring;
return 0;
err_ring:
intel_ring_unpin(ce->ring);
err_put:
intel_context_put(ce);
return err;
}
int intel_context_active_acquire(struct intel_context *ce)
{
int err;
err = i915_active_acquire(&ce->active);
if (err)
return err;
/* Preallocate tracking nodes */
if (!i915_gem_context_is_kernel(ce->gem_context)) {
err = i915_active_acquire_preallocate_barrier(&ce->active,
ce->engine);
if (err)
goto err_state;
if (err) {
i915_active_release(&ce->active);
return err;
}
}
return 0;
}
err_state:
__context_unpin_state(ce->state);
err_ring:
intel_ring_unpin(ce->ring);
err_put:
intel_context_put(ce);
return err;
void intel_context_active_release(struct intel_context *ce)
{
/* Nodes preallocated in intel_context_active() */
i915_active_acquire_barrier(&ce->active);
i915_active_release(&ce->active);
}
void
......@@ -301,3 +319,7 @@ struct i915_request *intel_context_create_request(struct intel_context *ce)
return rq;
}
#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftest_context.c"
#endif
......@@ -104,17 +104,8 @@ static inline void intel_context_exit(struct intel_context *ce)
ce->ops->exit(ce);
}
static inline int intel_context_active_acquire(struct intel_context *ce)
{
return i915_active_acquire(&ce->active);
}
static inline void intel_context_active_release(struct intel_context *ce)
{
/* Nodes preallocated in intel_context_active() */
i915_active_acquire_barrier(&ce->active);
i915_active_release(&ce->active);
}
int intel_context_active_acquire(struct intel_context *ce);
void intel_context_active_release(struct intel_context *ce);
static inline struct intel_context *intel_context_get(struct intel_context *ce)
{
......
......@@ -90,7 +90,7 @@ static bool switch_to_kernel_context(struct intel_engine_cs *engine)
/* Check again on the next retirement. */
engine->wakeref_serial = engine->serial + 1;
i915_request_add_barriers(rq);
i915_request_add_active_barriers(rq);
__i915_request_commit(rq);
return false;
......
/*
* SPDX-License-Identifier: GPL-2.0
*
* Copyright © 2019 Intel Corporation
*/
#include "i915_selftest.h"
#include "intel_gt.h"
#include "gem/selftests/mock_context.h"
#include "selftests/igt_flush_test.h"
#include "selftests/mock_drm.h"
static int request_sync(struct i915_request *rq)
{
long timeout;
int err = 0;
i915_request_get(rq);
i915_request_add(rq);
timeout = i915_request_wait(rq, 0, HZ / 10);
if (timeout < 0)
err = timeout;
else
i915_request_retire_upto(rq);
i915_request_put(rq);
return err;
}
static int context_sync(struct intel_context *ce)
{
struct intel_timeline *tl = ce->ring->timeline;
int err = 0;
do {
struct i915_request *rq;
long timeout;
rcu_read_lock();
rq = rcu_dereference(tl->last_request.request);
if (rq)
rq = i915_request_get_rcu(rq);
rcu_read_unlock();
if (!rq)
break;
timeout = i915_request_wait(rq, 0, HZ / 10);
if (timeout < 0)
err = timeout;
else
i915_request_retire_upto(rq);
i915_request_put(rq);
} while (!err);
return err;
}
static int __live_active_context(struct intel_engine_cs *engine,
struct i915_gem_context *fixme)
{
struct intel_context *ce;
int pass;
int err;
/*
* We keep active contexts alive until after a subsequent context
* switch as the final write from the context-save will be after
* we retire the final request. We track when we unpin the context,
* under the presumption that the final pin is from the last request,
* and instead of immediately unpinning the context, we add a task
* to unpin the context from the next idle-barrier.
*
* This test makes sure that the context is kept alive until a
* subsequent idle-barrier (emitted when the engine wakeref hits 0
* with no more outstanding requests).
*/
if (intel_engine_pm_is_awake(engine)) {
pr_err("%s is awake before starting %s!\n",
engine->name, __func__);
return -EINVAL;
}
ce = intel_context_create(fixme, engine);
if (!ce)
return -ENOMEM;
for (pass = 0; pass <= 2; pass++) {
struct i915_request *rq;
rq = intel_context_create_request(ce);
if (IS_ERR(rq)) {
err = PTR_ERR(rq);
goto err;
}
err = request_sync(rq);
if (err)
goto err;
/* Context will be kept active until after an idle-barrier. */
if (i915_active_is_idle(&ce->active)) {
pr_err("context is not active; expected idle-barrier (%s pass %d)\n",
engine->name, pass);
err = -EINVAL;
goto err;
}
if (!intel_engine_pm_is_awake(engine)) {
pr_err("%s is asleep before idle-barrier\n",
engine->name);
err = -EINVAL;
goto err;
}
}
/* Now make sure our idle-barriers are flushed */
err = context_sync(engine->kernel_context);
if (err)
goto err;
if (!i915_active_is_idle(&ce->active)) {
pr_err("context is still active!");
err = -EINVAL;
}
if (intel_engine_pm_is_awake(engine)) {
struct drm_printer p = drm_debug_printer(__func__);
intel_engine_dump(engine, &p,
"%s is still awake after idle-barriers\n",
engine->name);
GEM_TRACE_DUMP();
err = -EINVAL;
goto err;
}
err:
intel_context_put(ce);
return err;
}
static int live_active_context(void *arg)
{
struct intel_gt *gt = arg;
struct intel_engine_cs *engine;
struct i915_gem_context *fixme;
enum intel_engine_id id;
struct drm_file *file;
int err = 0;
file = mock_file(gt->i915);
if (IS_ERR(file))
return PTR_ERR(file);
mutex_lock(&gt->i915->drm.struct_mutex);
fixme = live_context(gt->i915, file);
if (!fixme) {
err = -ENOMEM;
goto unlock;
}
for_each_engine(engine, gt->i915, id) {
err = __live_active_context(engine, fixme);
if (err)
break;
err = igt_flush_test(gt->i915, I915_WAIT_LOCKED);
if (err)
break;
}
unlock:
mutex_unlock(&gt->i915->drm.struct_mutex);
mock_file_free(gt->i915, file);
return err;
}
static int __remote_sync(struct intel_context *ce, struct intel_context *remote)
{
struct i915_request *rq;
int err;
err = intel_context_pin(remote);
if (err)
return err;
rq = intel_context_create_request(ce);
if (IS_ERR(rq)) {
err = PTR_ERR(rq);
goto unpin;
}
err = intel_context_prepare_remote_request(remote, rq);
if (err) {
i915_request_add(rq);
goto unpin;
}
err = request_sync(rq);
unpin:
intel_context_unpin(remote);
return err;
}
static int __live_remote_context(struct intel_engine_cs *engine,
struct i915_gem_context *fixme)
{
struct intel_context *local, *remote;
int pass;
int err;
/*
* Check that our idle barriers do not interfere with normal
* activity tracking. In particular, check that operating
* on the context image remotely (intel_context_prepare_remote_request),
* which inserts foreign fences into intel_context.active, does not
* clobber the idle-barrier.
*/
remote = intel_context_create(fixme, engine);
if (!remote)
return -ENOMEM;
local = intel_context_create(fixme, engine);
if (!local) {
err = -ENOMEM;
goto err_remote;
}
for (pass = 0; pass <= 2; pass++) {
err = __remote_sync(local, remote);
if (err)
break;
err = __remote_sync(engine->kernel_context, remote);
if (err)
break;
if (i915_active_is_idle(&remote->active)) {
pr_err("remote context is not active; expected idle-barrier (%s pass %d)\n",
engine->name, pass);
err = -EINVAL;
break;
}
}
intel_context_put(local);
err_remote:
intel_context_put(remote);
return err;
}
static int live_remote_context(void *arg)
{
struct intel_gt *gt = arg;
struct intel_engine_cs *engine;
struct i915_gem_context *fixme;
enum intel_engine_id id;
struct drm_file *file;
int err = 0;
file = mock_file(gt->i915);
if (IS_ERR(file))
return PTR_ERR(file);
mutex_lock(&gt->i915->drm.struct_mutex);
fixme = live_context(gt->i915, file);
if (!fixme) {
err = -ENOMEM;
goto unlock;
}
for_each_engine(engine, gt->i915, id) {
err = __live_remote_context(engine, fixme);
if (err)
break;
err = igt_flush_test(gt->i915, I915_WAIT_LOCKED);
if (err)
break;
}
unlock:
mutex_unlock(&gt->i915->drm.struct_mutex);
mock_file_free(gt->i915, file);
return err;
}
int intel_context_live_selftests(struct drm_i915_private *i915)
{
static const struct i915_subtest tests[] = {
SUBTEST(live_active_context),
SUBTEST(live_remote_context),
};
struct intel_gt *gt = &i915->gt;
if (intel_gt_is_wedged(gt))
return 0;
return intel_gt_live_subtests(tests, gt);
}
......@@ -33,6 +33,38 @@ struct active_node {
u64 timeline;
};
static inline struct active_node *
node_from_active(struct i915_active_request *active)
{
return container_of(active, struct active_node, base);
}
#define take_preallocated_barriers(x) llist_del_all(&(x)->preallocated_barriers)
static inline bool is_barrier(const struct i915_active_request *active)
{
return IS_ERR(rcu_access_pointer(active->request));
}
static inline struct llist_node *barrier_to_ll(struct active_node *node)
{
GEM_BUG_ON(!is_barrier(&node->base));
return (struct llist_node *)&node->base.link;
}
static inline struct intel_engine_cs *
barrier_to_engine(struct active_node *node)
{
GEM_BUG_ON(!is_barrier(&node->base));
return (struct intel_engine_cs *)node->base.link.prev;
}
static inline struct active_node *barrier_from_ll(struct llist_node *x)
{
return container_of((struct list_head *)x,
struct active_node, base.link);
}
#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM) && IS_ENABLED(CONFIG_DEBUG_OBJECTS)
static void *active_debug_hint(void *addr)
......@@ -127,7 +159,7 @@ active_retire(struct i915_active *ref)
static void
node_retire(struct i915_active_request *base, struct i915_request *rq)
{
active_retire(container_of(base, struct active_node, base)->ref);
active_retire(node_from_active(base)->ref);
}
static struct i915_active_request *
......@@ -184,6 +216,7 @@ active_instance(struct i915_active *ref, u64 idx)
ref->cache = node;
mutex_unlock(&ref->mutex);
BUILD_BUG_ON(offsetof(typeof(*node), base));
return &node->base;
}
......@@ -201,11 +234,52 @@ void __i915_active_init(struct drm_i915_private *i915,
ref->retire = retire;
ref->tree = RB_ROOT;
ref->cache = NULL;
init_llist_head(&ref->barriers);
init_llist_head(&ref->preallocated_barriers);
atomic_set(&ref->count, 0);
__mutex_init(&ref->mutex, "i915_active", key);
}
static bool __active_del_barrier(struct i915_active *ref,
struct active_node *node)
{
struct intel_engine_cs *engine = barrier_to_engine(node);
struct llist_node *head = NULL, *tail = NULL;
struct llist_node *pos, *next;
GEM_BUG_ON(node->timeline != engine->kernel_context->ring->timeline->fence_context);
/*
* Rebuild the llist excluding our node. We may perform this
* outside of the kernel_context timeline mutex and so someone
* else may be manipulating the engine->barrier_tasks, in
* which case either we or they will be upset :)
*
* A second __active_del_barrier() will report failure to claim
* the active_node and the caller will just shrug and know not to
* claim ownership of its node.
*
* A concurrent i915_request_add_active_barriers() will miss adding
* any of the tasks, but we will try again on the next -- and since
* we are actively using the barrier, we know that there will be
* at least another opportunity when we idle.
*/
llist_for_each_safe(pos, next, llist_del_all(&engine->barrier_tasks)) {
if (node == barrier_from_ll(pos)) {
node = NULL;
continue;
}
pos->next = head;
head = pos;
if (!tail)
tail = pos;
}
if (head)
llist_add_batch(head, tail, &engine->barrier_tasks);
return !node;
}
int i915_active_ref(struct i915_active *ref,
u64 timeline,
struct i915_request *rq)
......@@ -224,8 +298,20 @@ int i915_active_ref(struct i915_active *ref,
goto out;
}
if (!i915_active_request_isset(active))
atomic_inc(&ref->count);
if (is_barrier(active)) { /* proto-node used by our idle barrier */
/*
* This request is on the kernel_context timeline, and so
* we can use it to substitute for the pending idle-barrer
* request that we want to emit on the kernel_context.
*/
__active_del_barrier(ref, node_from_active(active));
RCU_INIT_POINTER(active->request, NULL);
INIT_LIST_HEAD(&active->link);
} else {
if (!i915_active_request_isset(active))
atomic_inc(&ref->count);
}
GEM_BUG_ON(!atomic_read(&ref->count));
__i915_active_request_set(active, rq);
out:
......@@ -312,6 +398,11 @@ int i915_active_wait(struct i915_active *ref)
}
rbtree_postorder_for_each_entry_safe(it, n, &ref->tree, node) {
if (is_barrier(&it->base)) { /* unconnected idle-barrier */
err = -EBUSY;
break;
}
err = i915_active_request_retire(&it->base, BKL(ref));
if (err)
break;
......@@ -374,6 +465,92 @@ void i915_active_fini(struct i915_active *ref)
}
#endif
static inline bool is_idle_barrier(struct active_node *node, u64 idx)
{
return node->timeline == idx && !i915_active_request_isset(&node->base);
}
static struct active_node *reuse_idle_barrier(struct i915_active *ref, u64 idx)
{
struct rb_node *prev, *p;
if (RB_EMPTY_ROOT(&ref->tree))
return NULL;
mutex_lock(&ref->mutex);
GEM_BUG_ON(i915_active_is_idle(ref));
/*
* Try to reuse any existing barrier nodes already allocated for this
* i915_active, due to overlapping active phases there is likely a
* node kept alive (as we reuse before parking). We prefer to reuse
* completely idle barriers (less hassle in manipulating the llists),
* but otherwise any will do.
*/
if (ref->cache && is_idle_barrier(ref->cache, idx)) {
p = &ref->cache->node;
goto match;
}
prev = NULL;
p = ref->tree.rb_node;
while (p) {
struct active_node *node =
rb_entry(p, struct active_node, node);
if (is_idle_barrier(node, idx))
goto match;
prev = p;
if (node->timeline < idx)
p = p->rb_right;
else
p = p->rb_left;
}
/*
* No quick match, but we did find the leftmost rb_node for the
* kernel_context. Walk the rb_tree in-order to see if there were
* any idle-barriers on this timeline that we missed, or just use
* the first pending barrier.
*/
for (p = prev; p; p = rb_next(p)) {
struct active_node *node =
rb_entry(p, struct active_node, node);
if (node->timeline > idx)
break;
if (node->timeline < idx)
continue;
if (is_idle_barrier(node, idx))
goto match;
/*
* The list of pending barriers is protected by the
* kernel_context timeline, which notably we do not hold
* here. i915_request_add_active_barriers() may consume
* the barrier before we claim it, so we have to check
* for success.
*/
if (is_barrier(&node->base) && __active_del_barrier(ref, node))
goto match;
}
mutex_unlock(&ref->mutex);
return NULL;
match:
rb_erase(p, &ref->tree); /* Hide from waits and sibling allocations */
if (p == &ref->cache->node)
ref->cache = NULL;
mutex_unlock(&ref->mutex);
return rb_entry(p, struct active_node, node);
}
int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
struct intel_engine_cs *engine)
{
......@@ -382,39 +559,61 @@ int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
struct llist_node *pos, *next;
int err;
GEM_BUG_ON(!mask);
GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers));
/*
* Preallocate a node for each physical engine supporting the target
* engine (remember virtual engines have more than one sibling).
* We can then use the preallocated nodes in
* i915_active_acquire_barrier()
*/
for_each_engine_masked(engine, i915, mask, tmp) {
struct intel_context *kctx = engine->kernel_context;
u64 idx = engine->kernel_context->ring->timeline->fence_context;
struct active_node *node;
node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
if (unlikely(!node)) {
err = -ENOMEM;
goto unwind;
node = reuse_idle_barrier(ref, idx);
if (!node) {
node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
if (!node) {
err = ENOMEM;
goto unwind;
}
RCU_INIT_POINTER(node->base.request, NULL);
node->base.retire = node_retire;
node->timeline = idx;
node->ref = ref;
}
i915_active_request_init(&node->base,
(void *)engine, node_retire);
node->timeline = kctx->ring->timeline->fence_context;
node->ref = ref;
atomic_inc(&ref->count);
if (!i915_active_request_isset(&node->base)) {
/*
* Mark this as being *our* unconnected proto-node.
*
* Since this node is not in any list, and we have
* decoupled it from the rbtree, we can reuse the
* request to indicate this is an idle-barrier node
* and then we can use the rb_node and list pointers
* for our tracking of the pending barrier.
*/
RCU_INIT_POINTER(node->base.request, ERR_PTR(-EAGAIN));
node->base.link.prev = (void *)engine;
atomic_inc(&ref->count);
}
GEM_BUG_ON(barrier_to_engine(node) != engine);
llist_add(barrier_to_ll(node), &ref->preallocated_barriers);
intel_engine_pm_get(engine);
llist_add((struct llist_node *)&node->base.link,
&ref->barriers);
}
return 0;
unwind:
llist_for_each_safe(pos, next, llist_del_all(&ref->barriers)) {
struct active_node *node;
llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) {
struct active_node *node = barrier_from_ll(pos);
node = container_of((struct list_head *)pos,
typeof(*node), base.link);
engine = (void *)rcu_access_pointer(node->base.request);
atomic_dec(&ref->count);
intel_engine_pm_put(barrier_to_engine(node));
intel_engine_pm_put(engine);
kmem_cache_free(global.slab_cache, node);
}
return err;
......@@ -426,25 +625,27 @@ void i915_active_acquire_barrier(struct i915_active *ref)
GEM_BUG_ON(i915_active_is_idle(ref));
/*
* Transfer the list of preallocated barriers into the
* i915_active rbtree, but only as proto-nodes. They will be
* populated by i915_request_add_active_barriers() to point to the
* request that will eventually release them.
*/
mutex_lock_nested(&ref->mutex, SINGLE_DEPTH_NESTING);
llist_for_each_safe(pos, next, llist_del_all(&ref->barriers)) {
struct intel_engine_cs *engine;
struct active_node *node;
llist_for_each_safe(pos, next, take_preallocated_barriers(ref)) {
struct active_node *node = barrier_from_ll(pos);
struct intel_engine_cs *engine = barrier_to_engine(node);
struct rb_node **p, *parent;
node = container_of((struct list_head *)pos,
typeof(*node), base.link);
engine = (void *)rcu_access_pointer(node->base.request);
RCU_INIT_POINTER(node->base.request, ERR_PTR(-EAGAIN));
parent = NULL;
p = &ref->tree.rb_node;
while (*p) {
struct active_node *it;
parent = *p;
if (rb_entry(parent,
struct active_node,
node)->timeline < node->timeline)
it = rb_entry(parent, struct active_node, node);
if (it->timeline < node->timeline)
p = &parent->rb_right;
else
p = &parent->rb_left;
......@@ -452,20 +653,29 @@ void i915_active_acquire_barrier(struct i915_active *ref)
rb_link_node(&node->node, parent, p);
rb_insert_color(&node->node, &ref->tree);
llist_add((struct llist_node *)&node->base.link,
&engine->barrier_tasks);
llist_add(barrier_to_ll(node), &engine->barrier_tasks);
intel_engine_pm_put(engine);
}
mutex_unlock(&ref->mutex);
}
void i915_request_add_barriers(struct i915_request *rq)
void i915_request_add_active_barriers(struct i915_request *rq)
{
struct intel_engine_cs *engine = rq->engine;
struct llist_node *node, *next;
llist_for_each_safe(node, next, llist_del_all(&engine->barrier_tasks))
GEM_BUG_ON(intel_engine_is_virtual(engine));
GEM_BUG_ON(rq->timeline != engine->kernel_context->ring->timeline);
/*
* Attach the list of proto-fences to the in-flight request such
* that the parent i915_active will be released when this request
* is retired.
*/
llist_for_each_safe(node, next, llist_del_all(&engine->barrier_tasks)) {
RCU_INIT_POINTER(barrier_from_ll(node)->base.request, rq);
list_add_tail((struct list_head *)node, &rq->active_list);
}
}
int i915_active_request_set(struct i915_active_request *active,
......
......@@ -413,6 +413,6 @@ static inline void i915_active_fini(struct i915_active *ref) { }
int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
struct intel_engine_cs *engine);
void i915_active_acquire_barrier(struct i915_active *ref);
void i915_request_add_barriers(struct i915_request *rq);
void i915_request_add_active_barriers(struct i915_request *rq);
#endif /* _I915_ACTIVE_H_ */
......@@ -42,7 +42,7 @@ struct i915_active {
int (*active)(struct i915_active *ref);
void (*retire)(struct i915_active *ref);
struct llist_head barriers;
struct llist_head preallocated_barriers;
};
#endif /* _I915_ACTIVE_TYPES_H_ */
......@@ -15,6 +15,7 @@ selftest(workarounds, intel_workarounds_live_selftests)
selftest(timelines, intel_timeline_live_selftests)
selftest(requests, i915_request_live_selftests)
selftest(active, i915_active_live_selftests)
selftest(gt_contexts, intel_context_live_selftests)
selftest(objects, i915_gem_object_live_selftests)
selftest(mman, i915_gem_mman_live_selftests)
selftest(dmabuf, i915_gem_dmabuf_live_selftests)
......@@ -24,7 +25,7 @@ selftest(gtt, i915_gem_gtt_live_selftests)
selftest(gem, i915_gem_live_selftests)
selftest(evict, i915_gem_evict_live_selftests)
selftest(hugepages, i915_gem_huge_page_live_selftests)
selftest(contexts, i915_gem_context_live_selftests)
selftest(gem_contexts, i915_gem_context_live_selftests)
selftest(blt, i915_gem_object_blt_live_selftests)
selftest(client, i915_gem_client_blt_live_selftests)
selftest(reset, intel_reset_live_selftests)
......
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