[PATCH 2/9] drm/i915: Track all held rpm wakerefs

Chris Wilson chris at chris-wilson.co.uk
Fri Aug 10 12:58:45 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         |   8 +-
 drivers/gpu/drm/i915/i915_drv.h         |   7 +
 drivers/gpu/drm/i915/intel_drv.h        |  32 ++--
 drivers/gpu/drm/i915/intel_runtime_pm.c | 217 +++++++++++++++++++++---
 5 files changed, 233 insertions(+), 44 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..b6e83043ac9d 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -908,6 +908,7 @@ static int i915_driver_init_early(struct drm_i915_private *dev_priv,
 	mutex_init(&dev_priv->pps_mutex);
 
 	i915_memcpy_init_early(dev_priv);
+	intel_runtime_pm_init_early(dev_priv);
 
 	ret = i915_workqueues_init(dev_priv);
 	if (ret < 0)
@@ -1329,6 +1330,8 @@ static void i915_welcome_messages(struct drm_i915_private *dev_priv)
 		DRM_INFO("DRM_I915_DEBUG enabled\n");
 	if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
 		DRM_INFO("DRM_I915_DEBUG_GEM enabled\n");
+	if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_RPM))
+		DRM_INFO("DRM_I915_DEBUG_RPM enabled\n");
 }
 
 /**
@@ -1477,7 +1480,7 @@ 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)
@@ -1685,6 +1688,7 @@ static int i915_drm_suspend_late(struct drm_device *dev, bool hibernation)
 
 out:
 	enable_rpm_wakeref_asserts(dev_priv);
+	intel_runtime_pm_cleanup(dev_priv);
 
 	return ret;
 }
@@ -2644,7 +2648,7 @@ static int intel_runtime_suspend(struct device *kdev)
 	}
 
 	enable_rpm_wakeref_asserts(dev_priv);
-	WARN_ON_ONCE(atomic_read(&dev_priv->runtime_pm.wakeref_count));
+	intel_runtime_pm_cleanup(dev_priv);
 
 	if (intel_uncore_arm_unclaimed_mmio_detection(dev_priv))
 		DRM_ERROR("Unclaimed access detected prior to suspending\n");
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 5fa13887b911..6f2b81f135cf 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>
@@ -1287,6 +1288,12 @@ 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 364fc2504fa4..5942593f1732 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1950,6 +1950,7 @@ void intel_psr_short_pulse(struct intel_dp *intel_dp);
 int intel_psr_wait_for_idle(const struct intel_crtc_state *new_crtc_state);
 
 /* intel_runtime_pm.c */
+void intel_runtime_pm_init_early(struct drm_i915_private *dev_priv);
 int intel_power_domains_init(struct drm_i915_private *);
 void intel_power_domains_cleanup(struct drm_i915_private *dev_priv);
 void intel_power_domains_init_hw(struct drm_i915_private *dev_priv, bool resume);
@@ -1960,6 +1961,7 @@ 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);
 
@@ -1977,23 +1979,23 @@ void icl_dbuf_slices_update(struct drm_i915_private *dev_priv,
 			    u8 req_slices);
 
 static inline void
-assert_rpm_device_not_suspended(struct drm_i915_private *dev_priv)
+assert_rpm_device_not_suspended(struct drm_i915_private *i915)
 {
-	WARN_ONCE(dev_priv->runtime_pm.suspended,
+	WARN_ONCE(i915->runtime_pm.suspended,
 		  "Device suspended during HW access\n");
 }
 
 static inline void
-assert_rpm_wakelock_held(struct drm_i915_private *dev_priv)
+assert_rpm_wakelock_held(struct drm_i915_private *i915)
 {
-	assert_rpm_device_not_suspended(dev_priv);
-	WARN_ONCE(!atomic_read(&dev_priv->runtime_pm.wakeref_count),
+	assert_rpm_device_not_suspended(i915);
+	WARN_ONCE(!atomic_read(&i915->runtime_pm.wakeref_count),
 		  "RPM wakelock ref not held during HW access");
 }
 
 /**
  * disable_rpm_wakeref_asserts - disable the RPM assert checks
- * @dev_priv: i915 device instance
+ * @i915: i915 device instance
  *
  * This function disable asserts that check if we hold an RPM wakelock
  * reference, while keeping the device-not-suspended checks still enabled.
@@ -2010,14 +2012,14 @@ assert_rpm_wakelock_held(struct drm_i915_private *dev_priv)
  * enable_rpm_wakeref_asserts().
  */
 static inline void
-disable_rpm_wakeref_asserts(struct drm_i915_private *dev_priv)
+disable_rpm_wakeref_asserts(struct drm_i915_private *i915)
 {
-	atomic_inc(&dev_priv->runtime_pm.wakeref_count);
+	atomic_inc(&i915->runtime_pm.wakeref_count);
 }
 
 /**
  * enable_rpm_wakeref_asserts - re-enable the RPM assert checks
- * @dev_priv: i915 device instance
+ * @i915: i915 device instance
  *
  * This function re-enables the RPM assert checks after disabling them with
  * disable_rpm_wakeref_asserts. It's meant to be used only in special
@@ -2027,15 +2029,15 @@ disable_rpm_wakeref_asserts(struct drm_i915_private *dev_priv)
  * disable_rpm_wakeref_asserts().
  */
 static inline void
-enable_rpm_wakeref_asserts(struct drm_i915_private *dev_priv)
+enable_rpm_wakeref_asserts(struct drm_i915_private *i915)
 {
-	atomic_dec(&dev_priv->runtime_pm.wakeref_count);
+	atomic_dec(&i915->runtime_pm.wakeref_count);
 }
 
-void intel_runtime_pm_get(struct drm_i915_private *dev_priv);
-bool intel_runtime_pm_get_if_in_use(struct drm_i915_private *dev_priv);
-void intel_runtime_pm_get_noresume(struct drm_i915_private *dev_priv);
-void intel_runtime_pm_put(struct drm_i915_private *dev_priv);
+void intel_runtime_pm_get(struct drm_i915_private *i915);
+bool intel_runtime_pm_get_if_in_use(struct drm_i915_private *i915);
+void intel_runtime_pm_get_noresume(struct drm_i915_private *i915);
+void intel_runtime_pm_put(struct drm_i915_private *i915);
 
 void intel_display_set_init_power(struct drm_i915_private *dev, bool enable);
 
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 6e47061a5d21..61c905773f2c 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -49,6 +49,143 @@
  * present for a given platform.
  */
 
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_RPM)
+
+#include <linux/sort.h>
+
+#define STACKDEPTH 8
+
+static void init_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+	spin_lock_init(&i915->runtime_pm.debug_lock);
+}
+
+static noinline void
+track_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+	struct i915_runtime_pm *rpm = &i915->runtime_pm;
+	unsigned long entries[STACKDEPTH];
+	struct stack_trace trace = {
+		.entries = entries,
+		.max_entries = ARRAY_SIZE(entries),
+		.skip = 1
+	};
+	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(&rpm->debug_lock, flags);
+	stacks = krealloc(rpm->debug_owners,
+			  (rpm->debug_count + 1) * sizeof(*stacks),
+			  GFP_NOWAIT | __GFP_NOWARN);
+	if (stacks) {
+		stacks[rpm->debug_count++] = stack;
+		rpm->debug_owners = stacks;
+	}
+	spin_unlock_irqrestore(&rpm->debug_lock, flags);
+}
+
+static void untrack_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+	struct i915_runtime_pm *rpm = &i915->runtime_pm;
+	depot_stack_handle_t *stacks;
+	unsigned long flags;
+
+	spin_lock_irqsave(&rpm->debug_lock, flags);
+	stacks = fetch_and_zero(&rpm->debug_owners);
+	rpm->debug_count = 0;
+	spin_unlock_irqrestore(&rpm->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)
+{
+	struct i915_runtime_pm *rpm = &i915->runtime_pm;
+	unsigned long entries[STACKDEPTH];
+	depot_stack_handle_t *stacks;
+	unsigned long flags, count, i;
+	char *buf;
+
+	spin_lock_irqsave(&rpm->debug_lock, flags);
+	stacks = fetch_and_zero(&rpm->debug_owners);
+	count = fetch_and_zero(&rpm->debug_count);
+	spin_unlock_irqrestore(&rpm->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 init_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+}
+
+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);
 
@@ -3925,7 +4062,7 @@ void intel_power_domains_verify_state(struct drm_i915_private *dev_priv)
 
 /**
  * intel_runtime_pm_get - grab a runtime pm reference
- * @dev_priv: i915 device instance
+ * @i915: i915 device instance
  *
  * This function grabs a device-level runtime pm reference (mostly used for GEM
  * code to ensure the GTT or GT is on) and ensures that it is powered up.
@@ -3933,22 +4070,24 @@ void intel_power_domains_verify_state(struct drm_i915_private *dev_priv)
  * Any runtime pm reference obtained by this function must have a symmetric
  * call to intel_runtime_pm_put() to release the reference again.
  */
-void intel_runtime_pm_get(struct drm_i915_private *dev_priv)
+void intel_runtime_pm_get(struct drm_i915_private *i915)
 {
-	struct pci_dev *pdev = dev_priv->drm.pdev;
+	struct pci_dev *pdev = i915->drm.pdev;
 	struct device *kdev = &pdev->dev;
 	int ret;
 
 	ret = pm_runtime_get_sync(kdev);
 	WARN_ONCE(ret < 0, "pm_runtime_get_sync() failed: %d\n", ret);
 
-	atomic_inc(&dev_priv->runtime_pm.wakeref_count);
-	assert_rpm_wakelock_held(dev_priv);
+	atomic_inc(&i915->runtime_pm.wakeref_count);
+	assert_rpm_wakelock_held(i915);
+
+	track_intel_runtime_pm_wakeref(i915);
 }
 
 /**
  * intel_runtime_pm_get_if_in_use - grab a runtime pm reference if device in use
- * @dev_priv: i915 device instance
+ * @i915: i915 device instance
  *
  * This function grabs a device-level runtime pm reference if the device is
  * already in use and ensures that it is powered up. It is illegal to try
@@ -3959,10 +4098,10 @@ void intel_runtime_pm_get(struct drm_i915_private *dev_priv)
  *
  * Returns: True if the wakeref was acquired, or False otherwise.
  */
-bool intel_runtime_pm_get_if_in_use(struct drm_i915_private *dev_priv)
+bool intel_runtime_pm_get_if_in_use(struct drm_i915_private *i915)
 {
 	if (IS_ENABLED(CONFIG_PM)) {
-		struct pci_dev *pdev = dev_priv->drm.pdev;
+		struct pci_dev *pdev = i915->drm.pdev;
 		struct device *kdev = &pdev->dev;
 
 		/*
@@ -3975,15 +4114,17 @@ bool intel_runtime_pm_get_if_in_use(struct drm_i915_private *dev_priv)
 			return false;
 	}
 
-	atomic_inc(&dev_priv->runtime_pm.wakeref_count);
-	assert_rpm_wakelock_held(dev_priv);
+	atomic_inc(&i915->runtime_pm.wakeref_count);
+	assert_rpm_wakelock_held(i915);
+
+	track_intel_runtime_pm_wakeref(i915);
 
 	return true;
 }
 
 /**
  * intel_runtime_pm_get_noresume - grab a runtime pm reference
- * @dev_priv: i915 device instance
+ * @i915: i915 device instance
  *
  * This function grabs a device-level runtime pm reference (mostly used for GEM
  * code to ensure the GTT or GT is on).
@@ -3998,32 +4139,35 @@ bool intel_runtime_pm_get_if_in_use(struct drm_i915_private *dev_priv)
  * Any runtime pm reference obtained by this function must have a symmetric
  * call to intel_runtime_pm_put() to release the reference again.
  */
-void intel_runtime_pm_get_noresume(struct drm_i915_private *dev_priv)
+void intel_runtime_pm_get_noresume(struct drm_i915_private *i915)
 {
-	struct pci_dev *pdev = dev_priv->drm.pdev;
+	struct pci_dev *pdev = i915->drm.pdev;
 	struct device *kdev = &pdev->dev;
 
-	assert_rpm_wakelock_held(dev_priv);
+	assert_rpm_wakelock_held(i915);
 	pm_runtime_get_noresume(kdev);
 
-	atomic_inc(&dev_priv->runtime_pm.wakeref_count);
+	atomic_inc(&i915->runtime_pm.wakeref_count);
+
+	track_intel_runtime_pm_wakeref(i915);
 }
 
 /**
  * intel_runtime_pm_put - release a runtime pm reference
- * @dev_priv: i915 device instance
+ * @i915: i915 device instance
  *
  * This function drops the device-level runtime pm reference obtained by
  * intel_runtime_pm_get() and might power down the corresponding
  * hardware block right away if this is the last reference.
  */
-void intel_runtime_pm_put(struct drm_i915_private *dev_priv)
+void intel_runtime_pm_put(struct drm_i915_private *i915)
 {
-	struct pci_dev *pdev = dev_priv->drm.pdev;
+	struct pci_dev *pdev = i915->drm.pdev;
 	struct device *kdev = &pdev->dev;
 
-	assert_rpm_wakelock_held(dev_priv);
-	atomic_dec(&dev_priv->runtime_pm.wakeref_count);
+	assert_rpm_wakelock_held(i915);
+	if (atomic_dec_and_test(&i915->runtime_pm.wakeref_count))
+		untrack_intel_runtime_pm_wakeref(i915);
 
 	pm_runtime_mark_last_busy(kdev);
 	pm_runtime_put_autosuspend(kdev);
@@ -4031,7 +4175,7 @@ void intel_runtime_pm_put(struct drm_i915_private *dev_priv)
 
 /**
  * intel_runtime_pm_enable - enable runtime pm
- * @dev_priv: i915 device instance
+ * @i915: i915 device instance
  *
  * This function enables runtime pm at the end of the driver load sequence.
  *
@@ -4039,9 +4183,9 @@ void intel_runtime_pm_put(struct drm_i915_private *dev_priv)
  * subordinate display power domains. That is only done on the first modeset
  * using intel_display_set_init_power().
  */
-void intel_runtime_pm_enable(struct drm_i915_private *dev_priv)
+void intel_runtime_pm_enable(struct drm_i915_private *i915)
 {
-	struct pci_dev *pdev = dev_priv->drm.pdev;
+	struct pci_dev *pdev = i915->drm.pdev;
 	struct device *kdev = &pdev->dev;
 
 	pm_runtime_set_autosuspend_delay(kdev, 10000); /* 10s */
@@ -4053,7 +4197,7 @@ void intel_runtime_pm_enable(struct drm_i915_private *dev_priv)
 	 * so the driver's own RPM reference tracking asserts also work on
 	 * platforms without RPM support.
 	 */
-	if (!HAS_RUNTIME_PM(dev_priv)) {
+	if (!HAS_RUNTIME_PM(i915)) {
 		int ret;
 
 		pm_runtime_dont_use_autosuspend(kdev);
@@ -4071,9 +4215,9 @@ void intel_runtime_pm_enable(struct drm_i915_private *dev_priv)
 	pm_runtime_put_autosuspend(kdev);
 }
 
-void intel_runtime_pm_disable(struct drm_i915_private *dev_priv)
+void intel_runtime_pm_disable(struct drm_i915_private *i915)
 {
-	struct pci_dev *pdev = dev_priv->drm.pdev;
+	struct pci_dev *pdev = i915->drm.pdev;
 	struct device *kdev = &pdev->dev;
 
 	pm_runtime_dont_use_autosuspend(kdev);
@@ -4082,6 +4226,25 @@ void intel_runtime_pm_disable(struct drm_i915_private *dev_priv)
 	 * Remove the refcount we took in intel_runtime_pm_enable() in case
 	 * the platform doesn't support runtime PM.
 	 */
-	if (!HAS_RUNTIME_PM(dev_priv))
+	if (!HAS_RUNTIME_PM(i915))
 		pm_runtime_put(kdev);
 }
+
+void intel_runtime_pm_cleanup(struct drm_i915_private *i915)
+{
+	struct i915_runtime_pm *rpm = &i915->runtime_pm;
+
+	if (WARN(atomic_read(&rpm->wakeref_count),
+		 "i915->runtime_pm.wakeref_count=%d on cleanup\n",
+		 atomic_read(&rpm->wakeref_count))) {
+		show_intel_runtime_pm_wakeref(i915);
+		atomic_set(&rpm->wakeref_count, 0);
+	}
+
+	untrack_intel_runtime_pm_wakeref(i915);
+}
+
+void intel_runtime_pm_init_early(struct drm_i915_private *i915)
+{
+	init_intel_runtime_pm_wakeref(i915);
+}
-- 
2.18.0



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