Introduce a mutex to start locking the HW contexts independently of
struct_mutex, with a view to reducing the coarse struct_mutex. The
intel_context.pin_mutex is used to guard the transition to and from being
pinned on the gpu, and so is required before starting to build any
request. The intel_context will then remain pinned until the request
completes, but the mutex can be released immediately unpin completion of
pinning the context.
A slight variant of the above is used by per-context sseu that wants to
inspect the pinned status of the context, and requires that it remains
stable (either !pinned or pinned) across its operation. By using the
pin_mutex to serialise operations while pin_count==0, we can take that
pin_mutex for stabilise the boolean pin status.
v2: for Tvrtko!
* Improved commit message.
* Dropped _gpu suffix from gen8_modify_rpcs_gpu.
v3: Repair the locking for sseu selftests
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
Reviewed: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
---
drivers/gpu/drm/i915/i915_gem.c | 2 +-
drivers/gpu/drm/i915/i915_gem_context.c | 44 +++++++--------
drivers/gpu/drm/i915/intel_context.c | 58 +++++++++++++++++---
drivers/gpu/drm/i915/intel_context.h | 38 +++++++------
drivers/gpu/drm/i915/intel_context_types.h | 8 ++-
drivers/gpu/drm/i915/intel_lrc.c | 4 +-
drivers/gpu/drm/i915/intel_ringbuffer.c | 4 +-
drivers/gpu/drm/i915/selftests/mock_engine.c | 2 +-
8 files changed, 104 insertions(+), 56 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 0f32ec12896c..e7e8c236bc8e 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4667,7 +4667,7 @@ static int __intel_engines_record_defaults(struct
drm_i915_private *i915)
if (!state)
continue;
- GEM_BUG_ON(ce->pin_count);
+ GEM_BUG_ON(intel_context_is_pinned(ce));
/*
* As we will hold a reference to the logical state, it will
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c
b/drivers/gpu/drm/i915/i915_gem_context.c
index 995bc28d53d6..f9a21a891aa4 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -810,7 +810,6 @@ static int get_sseu(struct i915_gem_context *ctx,
struct drm_i915_gem_context_param_sseu user_sseu;
struct intel_engine_cs *engine;
struct intel_context *ce;
- int ret;
if (args->size == 0)
goto out;
@@ -830,21 +829,16 @@ static int get_sseu(struct i915_gem_context *ctx,
if (!engine)
return -EINVAL;
- ce = intel_context_instance(ctx, engine);
+ ce = intel_context_pin_lock(ctx, engine); /* serialises with set_sseu */
if (IS_ERR(ce))
return PTR_ERR(ce);
- /* Only use for mutex here is to serialize get_param and set_param. */
- ret = mutex_lock_interruptible(&ctx->i915->drm.struct_mutex);
- if (ret)
- return ret;
-
user_sseu.slice_mask = ce->sseu.slice_mask;
user_sseu.subslice_mask = ce->sseu.subslice_mask;
user_sseu.min_eus_per_subslice = ce->sseu.min_eus_per_subslice;
user_sseu.max_eus_per_subslice = ce->sseu.max_eus_per_subslice;
- mutex_unlock(&ctx->i915->drm.struct_mutex);
+ intel_context_pin_unlock(ce);
if (copy_to_user(u64_to_user_ptr(args->value), &user_sseu,
sizeof(user_sseu)))
@@ -940,23 +934,28 @@ static int gen8_emit_rpcs_config(struct i915_request *rq,
}
static int
-gen8_modify_rpcs_gpu(struct intel_context *ce,
- struct intel_engine_cs *engine,
- struct intel_sseu sseu)
+gen8_modify_rpcs(struct intel_context *ce, struct intel_sseu sseu)
{
- struct drm_i915_private *i915 = engine->i915;
+ struct drm_i915_private *i915 = ce->engine->i915;
struct i915_request *rq, *prev;
intel_wakeref_t wakeref;
int ret;
- GEM_BUG_ON(!ce->pin_count);
+ lockdep_assert_held(&ce->pin_mutex);
- lockdep_assert_held(&i915->drm.struct_mutex);
+ /*
+ * If the context is not idle, we have to submit an ordered request to
+ * modify its context image via the kernel context (writing to our own
+ * image, or into the registers directory, does not stick). Pristine
+ * and idle contexts will be configured on pinning.
+ */
+ if (!intel_context_is_pinned(ce))
+ return 0;
/* Submitting requests etc needs the hw awake. */
wakeref = intel_runtime_pm_get(i915);
- rq = i915_request_alloc(engine, i915->kernel_context);
+ rq = i915_request_alloc(ce->engine, i915->kernel_context);
if (IS_ERR(rq)) {
ret = PTR_ERR(rq);
goto out_put;
@@ -1010,25 +1009,20 @@ __i915_gem_context_reconfigure_sseu(struct
i915_gem_context *ctx,
GEM_BUG_ON(INTEL_GEN(ctx->i915) < 8);
GEM_BUG_ON(engine->id != RCS0);
- ce = intel_context_instance(ctx, engine);
+ ce = intel_context_pin_lock(ctx, engine);
if (IS_ERR(ce))
return PTR_ERR(ce);
/* Nothing to do if unmodified. */
if (!memcmp(&ce->sseu, &sseu, sizeof(sseu)))
- return 0;
-
- /*
- * If context is not idle we have to submit an ordered request to modify
- * its context image via the kernel context. Pristine and idle contexts
- * will be configured on pinning.
- */
- if (ce->pin_count)
- ret = gen8_modify_rpcs_gpu(ce, engine, sseu);
+ goto unlock;
+ ret = gen8_modify_rpcs(ce, sseu);
if (!ret)
ce->sseu = sseu;
+unlock:
+ intel_context_pin_unlock(ce);
return ret;
}
diff --git a/drivers/gpu/drm/i915/intel_context.c
b/drivers/gpu/drm/i915/intel_context.c
index 4c1dacb69f51..5a16c9bb2778 100644
--- a/drivers/gpu/drm/i915/intel_context.c
+++ b/drivers/gpu/drm/i915/intel_context.c
@@ -102,7 +102,7 @@ void __intel_context_remove(struct intel_context *ce)
spin_unlock(&ctx->hw_contexts_lock);
}
-struct intel_context *
+static struct intel_context *
intel_context_instance(struct i915_gem_context *ctx,
struct intel_engine_cs *engine)
{
@@ -126,6 +126,23 @@ intel_context_instance(struct i915_gem_context *ctx,
return pos;
}
+struct intel_context *
+intel_context_pin_lock(struct i915_gem_context *ctx,
+ struct intel_engine_cs *engine)
+ __acquires(ce->pin_mutex)
+{
+ struct intel_context *ce;
+
+ ce = intel_context_instance(ctx, engine);
+ if (IS_ERR(ce))
+ return ce;
+
+ if (mutex_lock_interruptible(&ce->pin_mutex))
+ return ERR_PTR(-EINTR);
+
+ return ce;
+}
+
struct intel_context *
intel_context_pin(struct i915_gem_context *ctx,
struct intel_engine_cs *engine)
@@ -133,16 +150,20 @@ intel_context_pin(struct i915_gem_context *ctx,
struct intel_context *ce;
int err;
- lockdep_assert_held(&ctx->i915->drm.struct_mutex);
-
ce = intel_context_instance(ctx, engine);
if (IS_ERR(ce))
return ce;
- if (unlikely(!ce->pin_count++)) {
+ if (likely(atomic_inc_not_zero(&ce->pin_count)))
+ return ce;
+
+ if (mutex_lock_interruptible(&ce->pin_mutex))
+ return ERR_PTR(-EINTR);
+
+ if (likely(!atomic_read(&ce->pin_count))) {
err = ce->ops->pin(ce);
if (err)
- goto err_unpin;
+ goto err;
mutex_lock(&ctx->mutex);
list_add(&ce->active_link, &ctx->active_engines);
@@ -150,16 +171,35 @@ intel_context_pin(struct i915_gem_context *ctx,
i915_gem_context_get(ctx);
GEM_BUG_ON(ce->gem_context != ctx);
+
+ smp_mb__before_atomic(); /* flush pin before it is visible */
}
- GEM_BUG_ON(!ce->pin_count); /* no overflow! */
+ atomic_inc(&ce->pin_count);
+ GEM_BUG_ON(!intel_context_is_pinned(ce)); /* no overflow! */
+
+ mutex_unlock(&ce->pin_mutex);
return ce;
-err_unpin:
- ce->pin_count = 0;
+err:
+ mutex_unlock(&ce->pin_mutex);
return ERR_PTR(err);
}
+void intel_context_unpin(struct intel_context *ce)
+{
+ if (likely(atomic_add_unless(&ce->pin_count, -1, 1)))
+ return;
+
+ /* We may be called from inside intel_context_pin() to evict another */
+ mutex_lock_nested(&ce->pin_mutex, SINGLE_DEPTH_NESTING);
+
+ if (likely(atomic_dec_and_test(&ce->pin_count)))
+ ce->ops->unpin(ce);
+
+ mutex_unlock(&ce->pin_mutex);
+}
+
static void intel_context_retire(struct i915_active_request *active,
struct i915_request *rq)
{
@@ -181,6 +221,8 @@ intel_context_init(struct intel_context *ce,
INIT_LIST_HEAD(&ce->signal_link);
INIT_LIST_HEAD(&ce->signals);
+ mutex_init(&ce->pin_mutex);
+
/* Use the whole device by default */
ce->sseu = intel_device_default_sseu(ctx->i915);
diff --git a/drivers/gpu/drm/i915/intel_context.h
b/drivers/gpu/drm/i915/intel_context.h
index ea21473891f7..9546d932406a 100644
--- a/drivers/gpu/drm/i915/intel_context.h
+++ b/drivers/gpu/drm/i915/intel_context.h
@@ -7,6 +7,8 @@
#ifndef __INTEL_CONTEXT_H__
#define __INTEL_CONTEXT_H__
+#include <linux/lockdep.h>
+
#include "intel_context_types.h"
#include "intel_engine_types.h"
@@ -29,18 +31,30 @@ intel_context_lookup(struct i915_gem_context *ctx,
struct intel_engine_cs *engine);
/**
- * intel_context_instance - Lookup or allocate the HW context for (ctx, engine)
+ * intel_context_pin_lock - Stablises the 'pinned' status of the HW context
* @ctx - the parent GEM context
* @engine - the target HW engine
*
- * Returns the existing HW context for this pair of (GEM context, engine), or
- * allocates and initialises a fresh context. Once allocated, the HW context
- * remains resident until the GEM context is destroyed.
+ * Acquire a lock on the pinned status of the HW context, such that the context
+ * can neither be bound to the GPU or unbound whilst the lock is held, i.e.
+ * intel_context_is_pinned() remains stable.
*/
struct intel_context *
-intel_context_instance(struct i915_gem_context *ctx,
+intel_context_pin_lock(struct i915_gem_context *ctx,
struct intel_engine_cs *engine);
+static inline bool
+intel_context_is_pinned(struct intel_context *ce)
+{
+ return atomic_read(&ce->pin_count);
+}
+
+static inline void intel_context_pin_unlock(struct intel_context *ce)
+__releases(ce->pin_mutex)
+{
+ mutex_unlock(&ce->pin_mutex);
+}
+
struct intel_context *
__intel_context_insert(struct i915_gem_context *ctx,
struct intel_engine_cs *engine,
@@ -53,18 +67,10 @@ intel_context_pin(struct i915_gem_context *ctx, struct
intel_engine_cs *engine);
static inline void __intel_context_pin(struct intel_context *ce)
{
- GEM_BUG_ON(!ce->pin_count);
- ce->pin_count++;
+ GEM_BUG_ON(!intel_context_is_pinned(ce));
+ atomic_inc(&ce->pin_count);
}
-static inline void intel_context_unpin(struct intel_context *ce)
-{
- GEM_BUG_ON(!ce->pin_count);
- if (--ce->pin_count)
- return;
-
- GEM_BUG_ON(!ce->ops);
- ce->ops->unpin(ce);
-}
+void intel_context_unpin(struct intel_context *ce);
#endif /* __INTEL_CONTEXT_H__ */
diff --git a/drivers/gpu/drm/i915/intel_context_types.h
b/drivers/gpu/drm/i915/intel_context_types.h
index 804fa93de853..6dc9b4b9067b 100644
--- a/drivers/gpu/drm/i915/intel_context_types.h
+++ b/drivers/gpu/drm/i915/intel_context_types.h
@@ -8,6 +8,7 @@
#define __INTEL_CONTEXT_TYPES__
#include <linux/list.h>
+#include <linux/mutex.h>
#include <linux/rbtree.h>
#include <linux/types.h>
@@ -38,14 +39,19 @@ struct intel_context {
struct i915_gem_context *gem_context;
struct intel_engine_cs *engine;
struct intel_engine_cs *active;
+
struct list_head active_link;
struct list_head signal_link;
struct list_head signals;
+
struct i915_vma *state;
struct intel_ring *ring;
+
u32 *lrc_reg_state;
u64 lrc_desc;
- int pin_count;
+
+ atomic_t pin_count;
+ struct mutex pin_mutex; /* guards pinning and associated on-gpuing */
/**
* active_tracker: Active tracker for the external rq activity
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 44148433d237..748352d513d6 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1244,7 +1244,7 @@ static void __execlists_context_fini(struct intel_context
*ce)
static void execlists_context_destroy(struct intel_context *ce)
{
- GEM_BUG_ON(ce->pin_count);
+ GEM_BUG_ON(intel_context_is_pinned(ce));
if (ce->state)
__execlists_context_fini(ce);
@@ -1481,7 +1481,7 @@ static int execlists_request_alloc(struct i915_request
*request)
{
int ret;
- GEM_BUG_ON(!request->hw_context->pin_count);
+ GEM_BUG_ON(!intel_context_is_pinned(request->hw_context));
/*
* Flush enough space to reduce the likelihood of waiting after
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c
b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 03656021d04c..cc4fcd89b845 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1357,7 +1357,7 @@ static void __ring_context_fini(struct intel_context *ce)
static void ring_context_destroy(struct intel_context *ce)
{
- GEM_BUG_ON(ce->pin_count);
+ GEM_BUG_ON(intel_context_is_pinned(ce));
if (ce->state)
__ring_context_fini(ce);
@@ -1918,7 +1918,7 @@ static int ring_request_alloc(struct i915_request
*request)
{
int ret;
- GEM_BUG_ON(!request->hw_context->pin_count);
+ GEM_BUG_ON(!intel_context_is_pinned(request->hw_context));
GEM_BUG_ON(request->timeline->has_initial_breadcrumb);
/*
diff --git a/drivers/gpu/drm/i915/selftests/mock_engine.c
b/drivers/gpu/drm/i915/selftests/mock_engine.c
index 99d7463218d0..f6d120e05ee4 100644
--- a/drivers/gpu/drm/i915/selftests/mock_engine.c
+++ b/drivers/gpu/drm/i915/selftests/mock_engine.c
@@ -131,7 +131,7 @@ static void mock_context_unpin(struct intel_context *ce)
static void mock_context_destroy(struct intel_context *ce)
{
- GEM_BUG_ON(ce->pin_count);
+ GEM_BUG_ON(intel_context_is_pinned(ce));
if (ce->ring)
mock_ring_free(ce->ring);
--
2.20.1
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