drm/i915: rework dev->first_error locking

- reduce the irq disabled section, even for a debugfs file this was
  way too long.
- always disable irqs when taking the lock.

v2: Thou shalt not mistake locking for reference counting, so:
- reference count the error_state to protect from concurent freeeing.
  This will be only really used in the next patch.

Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 192b27e..72c73de 100644 (file)
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -698,12 +698,16 @@ static int i915_error_state(struct seq_file *m, void *unused)
        int i, j, page, offset, elt;
 
        spin_lock_irqsave(&dev_priv->error_lock, flags);
-       if (!dev_priv->first_error) {
+       error = dev_priv->first_error;
+       if (error)
+               kref_get(&error->ref);
+       spin_unlock_irqrestore(&dev_priv->error_lock, flags);
+
+       if (!error) {
                seq_printf(m, "no error state collected\n");
-               goto out;
+               return 0;
        }
 
-       error = dev_priv->first_error;
 
        seq_printf(m, "Time: %ld s %ld us\n", error->time.tv_sec,
                   error->time.tv_usec);
@@ -786,8 +790,7 @@ static int i915_error_state(struct seq_file *m, void *unused)
        if (error->display)
                intel_display_print_error_state(m, dev, error->display);
 
-out:
-       spin_unlock_irqrestore(&dev_priv->error_lock, flags);
+       kref_put(&error->ref, i915_error_state_free);
 
        return 0;
 }

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 090ec20..c070a2b 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -39,6 +39,7 @@
 #include <drm/intel-gtt.h>
 #include <linux/backlight.h>
 #include <linux/intel-iommu.h>
+#include <linux/kref.h>
 
 /* General customization:
  */
@@ -171,6 +172,7 @@ struct sdvo_device_mapping {
 struct intel_display_error_state;
 
 struct drm_i915_error_state {
+       struct kref ref;
        u32 eir;
        u32 pgtbl_er;
        u32 ier;
@@ -465,6 +467,7 @@ typedef struct drm_i915_private {
        unsigned int fsb_freq, mem_freq, is_ddr3;
 
        spinlock_t error_lock;
+       /* Protected by dev->error_lock. */
        struct drm_i915_error_state *first_error;
        struct work_struct error_work;
        struct completion error_completion;
@@ -1163,6 +1166,8 @@ void i915_handle_error(struct drm_device *dev, bool wedged);
 
 extern void intel_irq_init(struct drm_device *dev);
 
+void i915_error_state_free(struct kref *error_ref);
+
 void
 i915_enable_pipestat(drm_i915_private_t *dev_priv, int pipe, u32 mask);
 

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 49e5d3e..8334550 100644 (file)
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -850,10 +850,11 @@ i915_error_object_free(struct drm_i915_error_object *obj)
        kfree(obj);
 }
 
-static void
-i915_error_state_free(struct drm_device *dev,
-                     struct drm_i915_error_state *error)
+void
+i915_error_state_free(struct kref *error_ref)
 {
+       struct drm_i915_error_state *error = container_of(error_ref,
+                                                         typeof(*error), ref);
        int i;
 
        for (i = 0; i < ARRAY_SIZE(error->ring); i++) {
@@ -1102,6 +1103,7 @@ static void i915_capture_error_state(struct drm_device *dev)
        DRM_INFO("capturing error event; look for more information in /debug/dri/%d/i915_error_state\n",
                 dev->primary->index);
 
+       kref_init(&error->ref);
        error->eir = I915_READ(EIR);
        error->pgtbl_er = I915_READ(PGTBL_ER);
 
@@ -1173,7 +1175,7 @@ static void i915_capture_error_state(struct drm_device *dev)
        spin_unlock_irqrestore(&dev_priv->error_lock, flags);
 
        if (error)
-               i915_error_state_free(dev, error);
+               i915_error_state_free(&error->ref);
 }
 
 void i915_destroy_error_state(struct drm_device *dev)
@@ -1188,7 +1190,7 @@ void i915_destroy_error_state(struct drm_device *dev)
        spin_unlock_irqrestore(&dev_priv->error_lock, flags);
 
        if (error)
-               i915_error_state_free(dev, error);
+               kref_put(&error->ref, i915_error_state_free);
 }
 #else
 #define i915_capture_error_state(x)