drm/i915: Remove intel_context.active_link

We no longer need to track the active intel_contexts within each engine,
allowing us to drop a tricky mutex_lock from inside unpin (which may
occur inside fs_reclaim).
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/20190426163336.15906-8-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_context.c

@@ -49,7 +49,6 @@ int __intel_context_do_pin(struct intel_context *ce)
 		return -EINTR;
 
 	if (likely(!atomic_read(&ce->pin_count))) {
-		struct i915_gem_context *ctx = ce->gem_context;
 		intel_wakeref_t wakeref;
 
 		err = 0;
@@ -58,11 +57,7 @@ int __intel_context_do_pin(struct intel_context *ce)
 		if (err)
 			goto err;
 
-		i915_gem_context_get(ctx);
-
-		mutex_lock(&ctx->mutex);
-		list_add(&ce->active_link, &ctx->active_engines);
-		mutex_unlock(&ctx->mutex);
+		i915_gem_context_get(ce->gem_context); /* for ctx->ppgtt */
 
 		intel_context_get(ce);
 		smp_mb__before_atomic(); /* flush pin before it is visible */
@@ -91,10 +86,6 @@ void intel_context_unpin(struct intel_context *ce)
 	if (likely(atomic_dec_and_test(&ce->pin_count))) {
 		ce->ops->unpin(ce);
 
-		mutex_lock(&ce->gem_context->mutex);
-		list_del(&ce->active_link);
-		mutex_unlock(&ce->gem_context->mutex);
-
 		i915_gem_context_put(ce->gem_context);
 		intel_context_put(ce);
 	}

drivers/gpu/drm/i915/gt/intel_context_types.h

@@ -38,7 +38,6 @@ struct intel_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;
 

drivers/gpu/drm/i915/i915_debugfs.c

@@ -34,6 +34,7 @@
 
 #include "gt/intel_reset.h"
 
+#include "i915_gem_context.h"
 #include "intel_dp.h"
 #include "intel_drv.h"
 #include "intel_fbc.h"
@@ -397,14 +398,17 @@ static void print_context_stats(struct seq_file *m,
 	struct i915_gem_context *ctx;
 
 	list_for_each_entry(ctx, &i915->contexts.list, link) {
+		struct i915_gem_engines_iter it;
 		struct intel_context *ce;
 
-		list_for_each_entry(ce, &ctx->active_engines, active_link) {
+		for_each_gem_engine(ce,
+				    i915_gem_context_lock_engines(ctx), it) {
 			if (ce->state)
 				per_file_stats(0, ce->state->obj, &kstats);
 			if (ce->ring)
 				per_file_stats(0, ce->ring->vma->obj, &kstats);
 		}
+		i915_gem_context_unlock_engines(ctx);
 
 		if (!IS_ERR_OR_NULL(ctx->file_priv)) {
 			struct file_stats stats = { .vm = &ctx->ppgtt->vm, };
@@ -1882,6 +1886,7 @@ static int i915_context_status(struct seq_file *m, void *unused)
 		return ret;
 
 	list_for_each_entry(ctx, &dev_priv->contexts.list, link) {
+		struct i915_gem_engines_iter it;
 		struct intel_context *ce;
 
 		seq_puts(m, "HW context ");
@@ -1906,7 +1911,8 @@ static int i915_context_status(struct seq_file *m, void *unused)
 		seq_putc(m, ctx->remap_slice ? 'R' : 'r');
 		seq_putc(m, '\n');
 
-		list_for_each_entry(ce, &ctx->active_engines, active_link) {
+		for_each_gem_engine(ce,
+				    i915_gem_context_lock_engines(ctx), it) {
 			seq_printf(m, "%s: ", ce->engine->name);
 			if (ce->state)
 				describe_obj(m, ce->state->obj);
@@ -1914,6 +1920,7 @@ static int i915_context_status(struct seq_file *m, void *unused)
 				describe_ctx_ring(m, ce->ring);
 			seq_putc(m, '\n');
 		}
+		i915_gem_context_unlock_engines(ctx);
 
 		seq_putc(m, '\n');
 	}

drivers/gpu/drm/i915/i915_gem_context.c

@@ -289,7 +289,6 @@ static void i915_gem_context_free(struct i915_gem_context *ctx)
 {
 	lockdep_assert_held(&ctx->i915->drm.struct_mutex);
 	GEM_BUG_ON(!i915_gem_context_is_closed(ctx));
-	GEM_BUG_ON(!list_empty(&ctx->active_engines));
 
 	release_hw_id(ctx);
 	i915_ppgtt_put(ctx->ppgtt);
@@ -416,7 +415,6 @@ __create_context(struct drm_i915_private *dev_priv)
 	list_add_tail(&ctx->link, &dev_priv->contexts.list);
 	ctx->i915 = dev_priv;
 	ctx->sched.priority = I915_USER_PRIORITY(I915_PRIORITY_NORMAL);
-	INIT_LIST_HEAD(&ctx->active_engines);
 	mutex_init(&ctx->mutex);
 
 	mutex_init(&ctx->engines_mutex);

drivers/gpu/drm/i915/i915_gem_context_types.h

@@ -165,7 +165,6 @@ struct i915_gem_context {
 	atomic_t hw_id_pin_count;
 	struct list_head hw_id_link;
 
-	struct list_head active_engines;
 	struct mutex mutex;
 
 	struct i915_sched_attr sched;

drivers/gpu/drm/i915/selftests/i915_gem_context.c

@@ -1675,7 +1675,6 @@ static int mock_context_barrier(void *arg)
 		goto out;
 	}
 	i915_request_add(rq);
-	GEM_BUG_ON(list_empty(&ctx->active_engines));
 
 	counter = 0;
 	context_barrier_inject_fault = BIT(RCS0);

drivers/gpu/drm/i915/selftests/mock_context.c

@@ -50,7 +50,6 @@ mock_context(struct drm_i915_private *i915,
 	INIT_RADIX_TREE(&ctx->handles_vma, GFP_KERNEL);
 	INIT_LIST_HEAD(&ctx->handles_list);
 	INIT_LIST_HEAD(&ctx->hw_id_link);
-	INIT_LIST_HEAD(&ctx->active_engines);
 	mutex_init(&ctx->mutex);
 
 	ret = i915_gem_context_pin_hw_id(ctx);