Re: [PATCH 01/26] drm/i915/guc: Move GuC guc_id allocation under submission state sub-struct

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On 10/4/2021 15:06, Matthew Brost wrote:
Move guc_id allocation under submission state sub-struct as a future
patch will reuse the spin lock as a global submission state lock. Moving
this into sub-struct makes ownership of fields / lock clear.

Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
---
  drivers/gpu/drm/i915/gt/intel_context_types.h |  6 +-
  drivers/gpu/drm/i915/gt/uc/intel_guc.h        | 26 +++++----
  .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 56 ++++++++++---------
  3 files changed, 47 insertions(+), 41 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
index 12252c411159..e7e3984aab78 100644
--- a/drivers/gpu/drm/i915/gt/intel_context_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
@@ -197,18 +197,18 @@ struct intel_context {
  	struct {
  		/**
  		 * @id: handle which is used to uniquely identify this context
-		 * with the GuC, protected by guc->contexts_lock
+		 * with the GuC, protected by guc->submission_state.lock
  		 */
  		u16 id;
  		/**
  		 * @ref: the number of references to the guc_id, when
  		 * transitioning in and out of zero protected by
-		 * guc->contexts_lock
+		 * guc->submission_state.lock
  		 */
  		atomic_t ref;
  		/**
  		 * @link: in guc->guc_id_list when the guc_id has no refs but is
-		 * still valid, protected by guc->contexts_lock
+		 * still valid, protected by guc->submission_state.lock
  		 */
  		struct list_head link;
  	} guc_id;
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
index 5dd174babf7a..65b5e8eeef96 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
@@ -70,17 +70,21 @@ struct intel_guc {
  		void (*disable)(struct intel_guc *guc);
  	} interrupts;
- /**
-	 * @contexts_lock: protects guc_ids, guc_id_list, ce->guc_id.id, and
-	 * ce->guc_id.ref when transitioning in and out of zero
-	 */
-	spinlock_t contexts_lock;
-	/** @guc_ids: used to allocate unique ce->guc_id.id values */
-	struct ida guc_ids;
-	/**
-	 * @guc_id_list: list of intel_context with valid guc_ids but no refs
-	 */
-	struct list_head guc_id_list;
+	struct {
+		/**
+		 * @lock: protects everything in submission_state
+		 */
+		spinlock_t lock;
The old version also mentioned 'ce->guc_id.ref'. Should this not also mention that transition? Or was the old comment inaccurate. I'm not seeing any actual behaviour changes in the patch.


+		/**
+		 * @guc_ids: used to allocate new guc_ids
+		 */
+		struct ida guc_ids;
+		/**
+		 * @guc_id_list: list of intel_context with valid guc_ids but no
+		 * refs
+		 */
+		struct list_head guc_id_list;
+	} submission_state;
/**
  	 * @submission_supported: tracks whether we support GuC submission on
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
index ba0de35f6323..ad5c18119d92 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -68,16 +68,16 @@
   * fence is used to stall all requests associated with this guc_id until the
   * corresponding G2H returns indicating the guc_id has been deregistered.
   *
- * guc_ids:
+ * submission_state.guc_ids:
   * Unique number associated with private GuC context data passed in during
   * context registration / submission / deregistration. 64k available. Simple ida
   * is used for allocation.
   *
- * Stealing guc_ids:
- * If no guc_ids are available they can be stolen from another context at
- * request creation time if that context is unpinned. If a guc_id can't be found
- * we punt this problem to the user as we believe this is near impossible to hit
- * during normal use cases.
+ * Stealing submission_state.guc_ids:
+ * If no submission_state.guc_ids are available they can be stolen from another
I would abbreviate this instance as well, submission_state.guc_id is quite the mouthful. Unless this somehow magically links back to the structure entry in the kerneldoc output?

John.

+ * context at request creation time if that context is unpinned. If a guc_id
+ * can't be found we punt this problem to the user as we believe this is near
+ * impossible to hit during normal use cases.
   *
   * Locking:
   * In the GuC submission code we have 3 basic spin locks which protect
@@ -89,7 +89,7 @@
   * sched_engine can be submitting at a time. Currently only one sched_engine is
   * used for all of GuC submission but that could change in the future.
   *
- * guc->contexts_lock
+ * guc->submission_state.lock
   * Protects guc_id allocation for the given GuC, i.e. only one context can be
   * doing guc_id allocation operations at a time for each GuC in the system.
   *
@@ -103,7 +103,7 @@
   *
   * Lock ordering rules:
   * sched_engine->lock -> ce->guc_state.lock
- * guc->contexts_lock -> ce->guc_state.lock
+ * guc->submission_state.lock -> ce->guc_state.lock
   *
   * Reset races:
   * When a full GT reset is triggered it is assumed that some G2H responses to
@@ -1148,9 +1148,9 @@ int intel_guc_submission_init(struct intel_guc *guc)
xa_init_flags(&guc->context_lookup, XA_FLAGS_LOCK_IRQ); - spin_lock_init(&guc->contexts_lock);
-	INIT_LIST_HEAD(&guc->guc_id_list);
-	ida_init(&guc->guc_ids);
+	spin_lock_init(&guc->submission_state.lock);
+	INIT_LIST_HEAD(&guc->submission_state.guc_id_list);
+	ida_init(&guc->submission_state.guc_ids);
return 0;
  }
@@ -1215,7 +1215,7 @@ static void guc_submit_request(struct i915_request *rq)
static int new_guc_id(struct intel_guc *guc)
  {
-	return ida_simple_get(&guc->guc_ids, 0,
+	return ida_simple_get(&guc->submission_state.guc_ids, 0,
  			      GUC_MAX_LRC_DESCRIPTORS, GFP_KERNEL |
  			      __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
  }
@@ -1223,7 +1223,8 @@ static int new_guc_id(struct intel_guc *guc)
  static void __release_guc_id(struct intel_guc *guc, struct intel_context *ce)
  {
  	if (!context_guc_id_invalid(ce)) {
-		ida_simple_remove(&guc->guc_ids, ce->guc_id.id);
+		ida_simple_remove(&guc->submission_state.guc_ids,
+				  ce->guc_id.id);
  		reset_lrc_desc(guc, ce->guc_id.id);
  		set_context_guc_id_invalid(ce);
  	}
@@ -1235,9 +1236,9 @@ static void release_guc_id(struct intel_guc *guc, struct intel_context *ce)
  {
  	unsigned long flags;
- spin_lock_irqsave(&guc->contexts_lock, flags);
+	spin_lock_irqsave(&guc->submission_state.lock, flags);
  	__release_guc_id(guc, ce);
-	spin_unlock_irqrestore(&guc->contexts_lock, flags);
+	spin_unlock_irqrestore(&guc->submission_state.lock, flags);
  }
static int steal_guc_id(struct intel_guc *guc)
@@ -1245,10 +1246,10 @@ static int steal_guc_id(struct intel_guc *guc)
  	struct intel_context *ce;
  	int guc_id;
- lockdep_assert_held(&guc->contexts_lock);
+	lockdep_assert_held(&guc->submission_state.lock);
- if (!list_empty(&guc->guc_id_list)) {
-		ce = list_first_entry(&guc->guc_id_list,
+	if (!list_empty(&guc->submission_state.guc_id_list)) {
+		ce = list_first_entry(&guc->submission_state.guc_id_list,
  				      struct intel_context,
  				      guc_id.link);
@@ -1273,7 +1274,7 @@ static int assign_guc_id(struct intel_guc *guc, u16 *out)
  {
  	int ret;
- lockdep_assert_held(&guc->contexts_lock);
+	lockdep_assert_held(&guc->submission_state.lock);
ret = new_guc_id(guc);
  	if (unlikely(ret < 0)) {
@@ -1295,7 +1296,7 @@ static int pin_guc_id(struct intel_guc *guc, struct intel_context *ce)
  	GEM_BUG_ON(atomic_read(&ce->guc_id.ref));
try_again:
-	spin_lock_irqsave(&guc->contexts_lock, flags);
+	spin_lock_irqsave(&guc->submission_state.lock, flags);
might_lock(&ce->guc_state.lock); @@ -1310,7 +1311,7 @@ static int pin_guc_id(struct intel_guc *guc, struct intel_context *ce)
  	atomic_inc(&ce->guc_id.ref);
out_unlock:
-	spin_unlock_irqrestore(&guc->contexts_lock, flags);
+	spin_unlock_irqrestore(&guc->submission_state.lock, flags);
/*
  	 * -EAGAIN indicates no guc_id are available, let's retire any
@@ -1346,11 +1347,12 @@ static void unpin_guc_id(struct intel_guc *guc, struct intel_context *ce)
  	if (unlikely(context_guc_id_invalid(ce)))
  		return;
- spin_lock_irqsave(&guc->contexts_lock, flags);
+	spin_lock_irqsave(&guc->submission_state.lock, flags);
  	if (!context_guc_id_invalid(ce) && list_empty(&ce->guc_id.link) &&
  	    !atomic_read(&ce->guc_id.ref))
-		list_add_tail(&ce->guc_id.link, &guc->guc_id_list);
-	spin_unlock_irqrestore(&guc->contexts_lock, flags);
+		list_add_tail(&ce->guc_id.link,
+			      &guc->submission_state.guc_id_list);
+	spin_unlock_irqrestore(&guc->submission_state.lock, flags);
  }
static int __guc_action_register_context(struct intel_guc *guc,
@@ -1921,16 +1923,16 @@ static void guc_context_destroy(struct kref *kref)
  	 * returns indicating this context has been deregistered the guc_id is
  	 * returned to the pool of available guc_id.
  	 */
-	spin_lock_irqsave(&guc->contexts_lock, flags);
+	spin_lock_irqsave(&guc->submission_state.lock, flags);
  	if (context_guc_id_invalid(ce)) {
-		spin_unlock_irqrestore(&guc->contexts_lock, flags);
+		spin_unlock_irqrestore(&guc->submission_state.lock, flags);
  		__guc_context_destroy(ce);
  		return;
  	}
if (!list_empty(&ce->guc_id.link))
  		list_del_init(&ce->guc_id.link);
-	spin_unlock_irqrestore(&guc->contexts_lock, flags);
+	spin_unlock_irqrestore(&guc->submission_state.lock, flags);
/* Seal race with Reset */
  	spin_lock_irqsave(&ce->guc_state.lock, flags);




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