drm/i915/guc: Log runtime should consist of both mapping and relay

Currently, we're treating relay and mapping of GuC log as a separate
concepts. We're also using inconsistent locking, sometimes using
relay_lock, sometimes using struct mutex.
Let's correct that. Anything touching the runtime is now serialized
using runtime.lock, while we're still using struct mutex as inner lock
for mapping.
We're still racy in setting the log level - but we'll take care of that
in the following patches.

v2: Tidy locking (Sagar)
v3: Remove obsoleted comment (Sagar)
Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180319095348.9716-2-michal.winiarski@intel.com

drivers/gpu/drm/i915/intel_guc_log.c

@@ -176,10 +176,7 @@ static int guc_log_relay_file_create(struct intel_guc_log *log)
 	struct dentry *log_dir;
 	int ret;
 
-	if (!i915_modparams.guc_log_level)
-		return 0;
-
-	mutex_lock(&log->runtime.relay_lock);
+	lockdep_assert_held(&log->runtime.lock);
 
 	/* For now create the log file in /sys/kernel/debug/dri/0 dir */
 	log_dir = dev_priv->drm.primary->debugfs_root;
@@ -198,29 +195,17 @@ static int guc_log_relay_file_create(struct intel_guc_log *log)
 	 */
 	if (!log_dir) {
 		DRM_ERROR("Debugfs dir not available yet for GuC log file\n");
-		ret = -ENODEV;
-		goto out_unlock;
+		return -ENODEV;
 	}
 
 	ret = relay_late_setup_files(log->runtime.relay_chan, "guc_log",
 				     log_dir);
 	if (ret < 0 && ret != -EEXIST) {
 		DRM_ERROR("Couldn't associate relay chan with file %d\n", ret);
-		goto out_unlock;
+		return ret;
 	}
 
-	ret = 0;
-
-out_unlock:
-	mutex_unlock(&log->runtime.relay_lock);
-	return ret;
-}
-
-static bool guc_log_has_relay(struct intel_guc_log *log)
-{
-	lockdep_assert_held(&log->runtime.relay_lock);
-
-	return log->runtime.relay_chan;
+	return 0;
 }
 
 static void guc_move_to_next_buf(struct intel_guc_log *log)
@@ -231,9 +216,6 @@ static void guc_move_to_next_buf(struct intel_guc_log *log)
 	 */
 	smp_wmb();
 
-	if (!guc_log_has_relay(log))
-		return;
-
 	/* All data has been written, so now move the offset of sub buffer. */
 	relay_reserve(log->runtime.relay_chan, log->vma->obj->base.size);
 
@@ -243,9 +225,6 @@ static void guc_move_to_next_buf(struct intel_guc_log *log)
 
 static void *guc_get_write_buffer(struct intel_guc_log *log)
 {
-	if (!guc_log_has_relay(log))
-		return NULL;
-
 	/*
 	 * Just get the base address of a new sub buffer and copy data into it
 	 * ourselves. NULL will be returned in no-overwrite mode, if all sub
@@ -306,14 +285,14 @@ static void guc_read_update_log_buffer(struct intel_guc_log *log)
 	void *src_data, *dst_data;
 	bool new_overflow;
 
+	mutex_lock(&log->runtime.lock);
+
 	if (WARN_ON(!log->runtime.buf_addr))
-		return;
+		goto out_unlock;
 
 	/* Get the pointer to shared GuC log buffer */
 	log_buf_state = src_data = log->runtime.buf_addr;
 
-	mutex_lock(&log->runtime.relay_lock);
-
 	/* Get the pointer to local buffer to store the logs */
 	log_buf_snapshot_state = dst_data = guc_get_write_buffer(log);
 
@@ -324,9 +303,8 @@ static void guc_read_update_log_buffer(struct intel_guc_log *log)
 		 */
 		DRM_ERROR_RATELIMITED("no sub-buffer to capture logs\n");
 		log->capture_miss_count++;
-		mutex_unlock(&log->runtime.relay_lock);
 
-		return;
+		goto out_unlock;
 	}
 
 	/* Actual logs are present from the 2nd page */
@@ -397,7 +375,8 @@ static void guc_read_update_log_buffer(struct intel_guc_log *log)
 
 	guc_move_to_next_buf(log);
 
-	mutex_unlock(&log->runtime.relay_lock);
+out_unlock:
+	mutex_unlock(&log->runtime.lock);
 }
 
 static void capture_logs_work(struct work_struct *work)
@@ -413,21 +392,21 @@ static bool guc_log_has_runtime(struct intel_guc_log *log)
 	return log->runtime.buf_addr;
 }
 
-static int guc_log_runtime_create(struct intel_guc_log *log)
+static int guc_log_map(struct intel_guc_log *log)
 {
 	struct intel_guc *guc = log_to_guc(log);
 	struct drm_i915_private *dev_priv = guc_to_i915(guc);
 	void *vaddr;
 	int ret;
 
-	lockdep_assert_held(&dev_priv->drm.struct_mutex);
+	lockdep_assert_held(&log->runtime.lock);
 
 	if (!log->vma)
 		return -ENODEV;
 
-	GEM_BUG_ON(guc_log_has_runtime(log));
-
+	mutex_lock(&dev_priv->drm.struct_mutex);
 	ret = i915_gem_object_set_to_wc_domain(log->vma->obj, true);
+	mutex_unlock(&dev_priv->drm.struct_mutex);
 	if (ret)
 		return ret;
 
@@ -447,14 +426,9 @@ static int guc_log_runtime_create(struct intel_guc_log *log)
 	return 0;
 }
 
-static void guc_log_runtime_destroy(struct intel_guc_log *log)
+static void guc_log_unmap(struct intel_guc_log *log)
 {
-	/*
-	 * It's possible that the runtime stuff was never allocated because
-	 * GuC log was disabled at the boot time.
-	 */
-	if (!guc_log_has_runtime(log))
-		return;
+	lockdep_assert_held(&log->runtime.lock);
 
 	i915_gem_object_unpin_map(log->vma->obj);
 	log->runtime.buf_addr = NULL;
@@ -462,7 +436,7 @@ static void guc_log_runtime_destroy(struct intel_guc_log *log)
 
 void intel_guc_log_init_early(struct intel_guc_log *log)
 {
-	mutex_init(&log->runtime.relay_lock);
+	mutex_init(&log->runtime.lock);
 	INIT_WORK(&log->runtime.flush_work, capture_logs_work);
 }
 
@@ -474,12 +448,7 @@ static int guc_log_relay_create(struct intel_guc_log *log)
 	size_t n_subbufs, subbuf_size;
 	int ret;
 
-	if (!i915_modparams.guc_log_level)
-		return 0;
-
-	mutex_lock(&log->runtime.relay_lock);
-
-	GEM_BUG_ON(guc_log_has_relay(log));
+	lockdep_assert_held(&log->runtime.lock);
 
 	 /* Keep the size of sub buffers same as shared log buffer */
 	subbuf_size = GUC_LOG_SIZE;
@@ -509,12 +478,9 @@ static int guc_log_relay_create(struct intel_guc_log *log)
 	GEM_BUG_ON(guc_log_relay_chan->subbuf_size < subbuf_size);
 	log->runtime.relay_chan = guc_log_relay_chan;
 
-	mutex_unlock(&log->runtime.relay_lock);
-
 	return 0;
 
 err:
-	mutex_unlock(&log->runtime.relay_lock);
 	/* logging will be off */
 	i915_modparams.guc_log_level = 0;
 	return ret;
@@ -522,20 +488,10 @@ static int guc_log_relay_create(struct intel_guc_log *log)
 
 static void guc_log_relay_destroy(struct intel_guc_log *log)
 {
-	mutex_lock(&log->runtime.relay_lock);
-
-	/*
-	 * It's possible that the relay was never allocated because
-	 * GuC log was disabled at the boot time.
-	 */
-	if (!guc_log_has_relay(log))
-		goto out_unlock;
+	lockdep_assert_held(&log->runtime.lock);
 
 	relay_close(log->runtime.relay_chan);
 	log->runtime.relay_chan = NULL;
-
-out_unlock:
-	mutex_unlock(&log->runtime.relay_lock);
 }
 
 static void guc_log_capture_logs(struct intel_guc_log *log)
@@ -621,7 +577,6 @@ int intel_guc_log_create(struct intel_guc_log *log)
 
 void intel_guc_log_destroy(struct intel_guc_log *log)
 {
-	guc_log_runtime_destroy(log);
 	i915_vma_unpin_and_release(&log->vma);
 }
 
@@ -699,52 +654,43 @@ int intel_guc_log_control_set(struct intel_guc_log *log, u64 val)
 
 int intel_guc_log_register(struct intel_guc_log *log)
 {
-	struct intel_guc *guc = log_to_guc(log);
-	struct drm_i915_private *i915 = guc_to_i915(guc);
 	int ret;
 
+	mutex_lock(&log->runtime.lock);
+
 	GEM_BUG_ON(guc_log_has_runtime(log));
 
-	/*
-	 * If log was disabled at boot time, then setup needed to handle
-	 * log buffer flush interrupts would not have been done yet, so
-	 * do that now.
-	 */
 	ret = guc_log_relay_create(log);
 	if (ret)
 		goto err;
 
-	mutex_lock(&i915->drm.struct_mutex);
-	ret = guc_log_runtime_create(log);
-	mutex_unlock(&i915->drm.struct_mutex);
-
+	ret = guc_log_map(log);
 	if (ret)
 		goto err_relay;
 
 	ret = guc_log_relay_file_create(log);
 	if (ret)
-		goto err_runtime;
+		goto err_unmap;
 
-	guc_flush_log_msg_enable(guc);
+	guc_flush_log_msg_enable(log_to_guc(log));
+
+	mutex_unlock(&log->runtime.lock);
 
 	return 0;
 
-err_runtime:
-	mutex_lock(&i915->drm.struct_mutex);
-	guc_log_runtime_destroy(log);
-	mutex_unlock(&i915->drm.struct_mutex);
+err_unmap:
+	guc_log_unmap(log);
 err_relay:
 	guc_log_relay_destroy(log);
 err:
+	mutex_unlock(&log->runtime.lock);
+
 	return ret;
 }
 
 void intel_guc_log_unregister(struct intel_guc_log *log)
 {
-	struct intel_guc *guc = log_to_guc(log);
-	struct drm_i915_private *i915 = guc_to_i915(guc);
-
-	guc_flush_log_msg_disable(guc);
+	guc_flush_log_msg_disable(log_to_guc(log));
 
 	/*
 	 * Once logging is disabled, GuC won't generate logs & send an
@@ -754,9 +700,12 @@ void intel_guc_log_unregister(struct intel_guc_log *log)
 	 */
 	guc_flush_logs(log);
 
-	mutex_lock(&i915->drm.struct_mutex);
-	guc_log_runtime_destroy(log);
-	mutex_unlock(&i915->drm.struct_mutex);
+	mutex_lock(&log->runtime.lock);
+
+	GEM_BUG_ON(!guc_log_has_runtime(log));
 
+	guc_log_unmap(log);
 	guc_log_relay_destroy(log);
+
+	mutex_unlock(&log->runtime.lock);
 }

drivers/gpu/drm/i915/intel_guc_log.h

@@ -49,8 +49,7 @@ struct intel_guc_log {
 		struct workqueue_struct *flush_wq;
 		struct work_struct flush_work;
 		struct rchan *relay_chan;
-		/* To serialize the access to relay_chan */
-		struct mutex relay_lock;
+		struct mutex lock;
 	} runtime;
 	/* logging related stats */
 	u32 capture_miss_count;