drm/i915: Track all held rpm wakerefs

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.

v2: Use skip=0 for unwinding the stack as it appears our noinline
function doesn't appear on the stack (nor does save_stack_trace itself!)
v3: Allow rpm->debug_count to disappear between inspections and so
avoid calling krealloc(0) as that may return a ZERO_PTR not NULL! (Mika)
v4: Show who last acquire/released the runtime pm

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Tested-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190114142129.24398-1-chris@chris-wilson.co.uk

1 files changed, 257 insertions, 28 deletions

diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 9e9501f82f06..08f809371bbd 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -29,6 +29,8 @@
 #include <linux/pm_runtime.h>
 #include <linux/vgaarb.h>
 
+#include <drm/drm_print.h>
+
 #include "i915_drv.h"
 #include "intel_drv.h"
 
@@ -49,6 +51,218 @@
  * present for a given platform.
  */
 
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_RUNTIME_PM)
+
+#include <linux/sort.h>
+
+#define STACKDEPTH 8
+
+static noinline depot_stack_handle_t __save_depot_stack(void)
+{
+        unsigned long entries[STACKDEPTH];
+        struct stack_trace trace = {
+                .entries = entries,
+                .max_entries = ARRAY_SIZE(entries),
+                .skip = 1,
+        };
+
+        save_stack_trace(&trace);
+        if (trace.nr_entries &&
+            trace.entries[trace.nr_entries - 1] == ULONG_MAX)
+                trace.nr_entries--;
+
+        return depot_save_stack(&trace, GFP_NOWAIT | __GFP_NOWARN);
+}
+
+static void __print_depot_stack(depot_stack_handle_t stack,
+                                char *buf, int sz, int indent)
+{
+        unsigned long entries[STACKDEPTH];
+        struct stack_trace trace = {
+                .entries = entries,
+                .max_entries = ARRAY_SIZE(entries),
+        };
+
+        depot_fetch_stack(stack, &trace);
+        snprint_stack_trace(buf, sz, &trace, indent);
+}
+
+static void init_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+        struct i915_runtime_pm *rpm = &i915->runtime_pm;
+
+        spin_lock_init(&rpm->debug.lock);
+}
+
+static noinline void
+track_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+        struct i915_runtime_pm *rpm = &i915->runtime_pm;
+        depot_stack_handle_t stack, *stacks;
+        unsigned long flags;
+
+        atomic_inc(&rpm->wakeref_count);
+        assert_rpm_wakelock_held(i915);
+
+        if (!HAS_RUNTIME_PM(i915))
+                return;
+
+        stack = __save_depot_stack();
+        if (!stack)
+                return;
+
+        spin_lock_irqsave(&rpm->debug.lock, flags);
+
+        if (!rpm->debug.count)
+                rpm->debug.last_acquire = stack;
+
+        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 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
+__print_intel_runtime_pm_wakeref(struct drm_printer *p,
+                                 const struct intel_runtime_pm_debug *dbg)
+{
+        unsigned long i;
+        char *buf;
+
+        buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+        if (!buf)
+                return;
+
+        if (dbg->last_acquire) {
+                __print_depot_stack(dbg->last_acquire, buf, PAGE_SIZE, 2);
+                drm_printf(p, "Wakeref last acquired:\n%s", buf);
+        }
+
+        if (dbg->last_release) {
+                __print_depot_stack(dbg->last_release, buf, PAGE_SIZE, 2);
+                drm_printf(p, "Wakeref last released:\n%s", buf);
+        }
+
+        drm_printf(p, "Wakeref count: %lu\n", dbg->count);
+
+        sort(dbg->owners, dbg->count, sizeof(*dbg->owners), cmphandle, NULL);
+
+        for (i = 0; i < dbg->count; i++) {
+                depot_stack_handle_t stack = dbg->owners[i];
+                unsigned long rep;
+
+                rep = 1;
+                while (i + 1 < dbg->count && dbg->owners[i + 1] == stack)
+                        rep++, i++;
+                __print_depot_stack(stack, buf, PAGE_SIZE, 2);
+                drm_printf(p, "Wakeref x%lu taken at:\n%s", rep, buf);
+        }
+
+        kfree(buf);
+}
+
+static noinline void
+untrack_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+        struct i915_runtime_pm *rpm = &i915->runtime_pm;
+        struct intel_runtime_pm_debug dbg = {};
+        struct drm_printer p;
+        unsigned long flags;
+
+        assert_rpm_wakelock_held(i915);
+        if (atomic_dec_and_lock_irqsave(&rpm->wakeref_count,
+                                        &rpm->debug.lock,
+                                        flags)) {
+                dbg = rpm->debug;
+
+                rpm->debug.owners = NULL;
+                rpm->debug.count = 0;
+                rpm->debug.last_release = __save_depot_stack();
+
+                spin_unlock_irqrestore(&rpm->debug.lock, flags);
+        }
+        if (!dbg.count)
+                return;
+
+        p = drm_debug_printer("i915");
+        __print_intel_runtime_pm_wakeref(&p, &dbg);
+
+        kfree(dbg.owners);
+}
+
+void print_intel_runtime_pm_wakeref(struct drm_i915_private *i915,
+                                    struct drm_printer *p)
+{
+        struct intel_runtime_pm_debug dbg = {};
+
+        do {
+                struct i915_runtime_pm *rpm = &i915->runtime_pm;
+                unsigned long alloc = dbg.count;
+                depot_stack_handle_t *s;
+
+                spin_lock_irq(&rpm->debug.lock);
+                dbg.count = rpm->debug.count;
+                if (dbg.count <= alloc) {
+                        memcpy(dbg.owners,
+                               rpm->debug.owners,
+                               dbg.count * sizeof(*s));
+                }
+                dbg.last_acquire = rpm->debug.last_acquire;
+                dbg.last_release = rpm->debug.last_release;
+                spin_unlock_irq(&rpm->debug.lock);
+                if (dbg.count <= alloc)
+                        break;
+
+                s = krealloc(dbg.owners, dbg.count * sizeof(*s), GFP_KERNEL);
+                if (!s)
+                        goto out;
+
+                dbg.owners = s;
+        } while (1);
+
+        __print_intel_runtime_pm_wakeref(p, &dbg);
+
+out:
+        kfree(dbg.owners);
+}
+
+#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)
+{
+        atomic_inc(&i915->runtime_pm.wakeref_count);
+        assert_rpm_wakelock_held(i915);
+}
+
+static void untrack_intel_runtime_pm_wakeref(struct drm_i915_private *i915)
+{
+        assert_rpm_wakelock_held(i915);
+        atomic_dec(&i915->runtime_pm.wakeref_count);
+}
+
+#endif
+
 bool intel_display_power_well_is_enabled(struct drm_i915_private *dev_priv,
                                          enum i915_power_well_id power_well_id);
 
@@ -3986,7 +4200,7 @@ static 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.
@@ -3994,22 +4208,21 @@ static 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);
+        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
@@ -4020,10 +4233,10 @@ 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;
 
                 /*
@@ -4036,15 +4249,14 @@ 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);
+        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).
@@ -4059,32 +4271,31 @@ 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);
+        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);
+        untrack_intel_runtime_pm_wakeref(i915);
 
         pm_runtime_mark_last_busy(kdev);
         pm_runtime_put_autosuspend(kdev);
@@ -4092,7 +4303,7 @@ 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.
  *
@@ -4100,9 +4311,9 @@ void intel_runtime_pm_put(struct drm_i915_private *dev_priv)
  * subordinate display power domains. That is done by
  * intel_power_domains_enable().
  */
-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;
 
         /*
@@ -4124,7 +4335,7 @@ 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);
@@ -4142,17 +4353,35 @@ 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;
 
         /* Transfer rpm ownership back to core */
-        WARN(pm_runtime_get_sync(&dev_priv->drm.pdev->dev) < 0,
+        WARN(pm_runtime_get_sync(kdev) < 0,
              "Failed to pass rpm ownership back to core\n");
 
         pm_runtime_dont_use_autosuspend(kdev);
 
-        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;
+        int count;
+
+        count = atomic_fetch_inc(&rpm->wakeref_count); /* balance untrack */
+        WARN(count,
+             "i915->runtime_pm.wakeref_count=%d on cleanup\n",
+             count);
+
+        untrack_intel_runtime_pm_wakeref(i915);
+}
+
+void intel_runtime_pm_init_early(struct drm_i915_private *i915)
+{
+        init_intel_runtime_pm_wakeref(i915);
+}