[Intel-gfx] [PATCH 2/2] drm/i915: Track all held rpm wakerefs

Chris Wilson chris at chris-wilson.co.uk
Thu Aug 9 09:16:35 UTC 2018


Everytime we take a wakeref, record the stack trace of where it was
taken; clearing the set if we ever drop back to no owners. For debugging
a rpm leak, we can look at all the current wakerefs and check if they
have a matching rpm_put.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/Kconfig.debug      |  13 +++
 drivers/gpu/drm/i915/i915_drv.c         |   3 +-
 drivers/gpu/drm/i915/i915_drv.h         |   7 ++
 drivers/gpu/drm/i915/intel_drv.h        |   1 +
 drivers/gpu/drm/i915/intel_runtime_pm.c | 143 +++++++++++++++++++++++-
 5 files changed, 165 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig.debug b/drivers/gpu/drm/i915/Kconfig.debug
index 459f8f88a34c..ed572a454e01 100644
--- a/drivers/gpu/drm/i915/Kconfig.debug
+++ b/drivers/gpu/drm/i915/Kconfig.debug
@@ -39,6 +39,19 @@ config DRM_I915_DEBUG
 
           If in doubt, say "N".
 
+config DRM_I915_DEBUG_RPM
+        bool "Insert extra checks into the runtime pm internals"
+        depends on DRM_I915
+        default n
+        select STACKDEPOT
+        help
+          Enable extra sanity checks (including BUGs) along the runtime pm
+          paths that may slow the system down and if hit hang the machine.
+
+          Recommended for driver developers only.
+
+          If in doubt, say "N".
+
 config DRM_I915_DEBUG_GEM
         bool "Insert extra checks into the GEM internals"
         default n
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 62ef105a241d..63992fe45dbf 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1477,7 +1477,7 @@ void i915_driver_unload(struct drm_device *dev)
 
 	intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);
 
-	WARN_ON(atomic_read(&dev_priv->runtime_pm.wakeref_count));
+	intel_runtime_pm_cleanup(dev_priv);
 }
 
 static void i915_driver_release(struct drm_device *dev)
@@ -2603,6 +2603,7 @@ static int intel_runtime_suspend(struct device *kdev)
 
 	DRM_DEBUG_KMS("Suspending device\n");
 
+	intel_runtime_pm_cleanup(dev_priv);
 	disable_rpm_wakeref_asserts(dev_priv);
 
 	/*
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 0b10a30b7d96..c8d5b896b155 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -45,6 +45,7 @@
 #include <linux/pm_qos.h>
 #include <linux/reservation.h>
 #include <linux/shmem_fs.h>
+#include <linux/stackdepot.h>
 
 #include <drm/drmP.h>
 #include <drm/intel-gtt.h>
@@ -1278,6 +1279,12 @@ struct i915_runtime_pm {
 	atomic_t wakeref_count;
 	bool suspended;
 	bool irqs_enabled;
+
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_RPM)
+	spinlock_t debug_lock;
+	depot_stack_handle_t *debug_owners;
+	unsigned long debug_count;
+#endif
 };
 
 enum intel_pipe_crc_source {
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index dc6c0cec9b36..968c9074f1a8 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1957,6 +1957,7 @@ void bxt_display_core_init(struct drm_i915_private *dev_priv, bool resume);
 void bxt_display_core_uninit(struct drm_i915_private *dev_priv);
 void intel_runtime_pm_enable(struct drm_i915_private *dev_priv);
 void intel_runtime_pm_disable(struct drm_i915_private *dev_priv);
+void intel_runtime_pm_cleanup(struct drm_i915_private *dev_priv);
 const char *
 intel_display_power_domain_str(enum intel_display_power_domain domain);
 
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index b78c3b48aa62..7f555a0ad2ee 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -49,6 +49,130 @@
  * present for a given platform.
  */
 
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_RPM)
+
+#include <linux/sort.h>
+
+#define STACKDEPTH 12
+
+static void track_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+	unsigned long entries[STACKDEPTH];
+	struct stack_trace trace = {
+		.entries = entries,
+		.max_entries = ARRAY_SIZE(entries),
+		.skip = 2
+	};
+	unsigned long flags;
+	depot_stack_handle_t stack, *stacks;
+
+	if (!HAS_RUNTIME_PM(i915))
+		return;
+
+	save_stack_trace(&trace);
+	if (trace.nr_entries &&
+	    trace.entries[trace.nr_entries - 1] == ULONG_MAX)
+		trace.nr_entries--;
+
+	stack = depot_save_stack(&trace, GFP_NOWAIT | __GFP_NOWARN);
+	if (!stack)
+		return;
+
+	spin_lock_irqsave(&i915->runtime_pm.debug_lock, flags);
+	stacks = krealloc(i915->runtime_pm.debug_owners,
+			  (i915->runtime_pm.debug_count + 1) * sizeof(*stacks),
+			  GFP_NOWAIT | __GFP_NOWARN);
+	if (stacks) {
+		stacks[i915->runtime_pm.debug_count++] = stack;
+		i915->runtime_pm.debug_owners = stacks;
+	}
+	spin_unlock_irqrestore(&i915->runtime_pm.debug_lock, flags);
+}
+
+static void untrack_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+	depot_stack_handle_t *stacks;
+	unsigned long flags;
+
+	spin_lock_irqsave(&i915->runtime_pm.debug_lock, flags);
+	stacks = fetch_and_zero(&i915->runtime_pm.debug_owners);
+	i915->runtime_pm.debug_count = 0;
+	spin_unlock_irqrestore(&i915->runtime_pm.debug_lock, flags);
+
+	kfree(stacks);
+}
+
+static int cmphandle(const void *_a, const void *_b)
+{
+        const depot_stack_handle_t * const a = _a, * const b = _b;
+
+        if (*a < *b)
+                return -1;
+        else if (*a > *b)
+                return 1;
+        else
+                return 0;
+}
+
+static void show_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+	unsigned long entries[STACKDEPTH];
+	depot_stack_handle_t *stacks;
+	unsigned long flags, count, i;
+	char *buf;
+
+	spin_lock_irqsave(&i915->runtime_pm.debug_lock, flags);
+	stacks = fetch_and_zero(&i915->runtime_pm.debug_owners);
+	count = fetch_and_zero(&i915->runtime_pm.debug_count);
+	spin_unlock_irqrestore(&i915->runtime_pm.debug_lock, flags);
+	if (!count)
+		return;
+
+	DRM_DEBUG_DRIVER("leaked %lu wakerefs\n", count);
+
+	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!buf)
+		goto out_stacks;
+
+	sort(stacks, count, sizeof(*stacks), cmphandle, NULL);
+
+	for (i = 0; i < count; i++) {
+		struct stack_trace trace = {
+			.entries = entries,
+			.max_entries = ARRAY_SIZE(entries),
+		};
+		depot_stack_handle_t stack = stacks[i];
+		unsigned long rep;
+
+		rep = 1;
+		while (i + 1 < count && stacks[i + 1] == stack)
+			rep++, i++;
+		depot_fetch_stack(stack, &trace);
+		snprint_stack_trace(buf, PAGE_SIZE, &trace, 0);
+		DRM_DEBUG_DRIVER("wakeref x%lu at\n%s", rep, buf);
+	}
+
+	kfree(buf);
+out_stacks:
+	kfree(stacks);
+}
+
+#else
+
+static void track_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+}
+
+static void untrack_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+}
+
+static void show_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+}
+
+#endif
+
 bool intel_display_power_well_is_enabled(struct drm_i915_private *dev_priv,
 					 enum i915_power_well_id power_well_id);
 
@@ -3939,6 +4063,8 @@ void intel_runtime_pm_get(struct drm_i915_private *dev_priv)
 
 	atomic_inc(&dev_priv->runtime_pm.wakeref_count);
 	assert_rpm_wakelock_held(dev_priv);
+
+	track_intel_runtime_pm_wakeref(dev_priv);
 }
 
 /**
@@ -3973,6 +4099,8 @@ bool intel_runtime_pm_get_if_in_use(struct drm_i915_private *dev_priv)
 	atomic_inc(&dev_priv->runtime_pm.wakeref_count);
 	assert_rpm_wakelock_held(dev_priv);
 
+	track_intel_runtime_pm_wakeref(dev_priv);
+
 	return true;
 }
 
@@ -4002,6 +4130,8 @@ void intel_runtime_pm_get_noresume(struct drm_i915_private *dev_priv)
 	pm_runtime_get_noresume(kdev);
 
 	atomic_inc(&dev_priv->runtime_pm.wakeref_count);
+
+	track_intel_runtime_pm_wakeref(dev_priv);
 }
 
 /**
@@ -4018,7 +4148,8 @@ void intel_runtime_pm_put(struct drm_i915_private *dev_priv)
 	struct device *kdev = &pdev->dev;
 
 	assert_rpm_wakelock_held(dev_priv);
-	atomic_dec(&dev_priv->runtime_pm.wakeref_count);
+	if (!atomic_dec_and_test(&dev_priv->runtime_pm.wakeref_count))
+		untrack_intel_runtime_pm_wakeref(dev_priv);
 
 	pm_runtime_mark_last_busy(kdev);
 	pm_runtime_put_autosuspend(kdev);
@@ -4080,3 +4211,13 @@ void intel_runtime_pm_disable(struct drm_i915_private *dev_priv)
 	if (!HAS_RUNTIME_PM(dev_priv))
 		pm_runtime_put(kdev);
 }
+
+void intel_runtime_pm_cleanup(struct drm_i915_private *dev_priv)
+{
+	if (WARN_ON(atomic_read(&dev_priv->runtime_pm.wakeref_count))) {
+		show_intel_runtime_pm_wakeref(dev_priv);
+		atomic_set(&dev_priv->runtime_pm.wakeref_count, 0);
+	}
+
+	untrack_intel_runtime_pm_wakeref(dev_priv);
+}
-- 
2.18.0



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