drm_fb_helper_is_bound() is used to check if DRM userspace is in control.
This is done by looking at the fb on the primary plane. By the time
fb-helper gets around to committing, it's possible that the facts have
changed.
Avoid this race by holding the drm_device->master_mutex lock while
committing. When DRM userspace does its first open, it will now wait
until fb-helper is done. The helper will stay away if there's a master.
Two igt tests fail with the new 'bail out if master' rule. Work around
this by relaxing this rule for drm_fb_helper_restore_fbdev_mode_unlocked()
until the tests have been fixed. Add todo entry for this.
Locking rule: Always take the fb-helper lock first.
v5: drm_fb_helper_restore_fbdev_mode_unlocked(): Use
restore_fbdev_mode_force()
v2:
- Remove drm_fb_helper_is_bound() (Daniel Vetter)
- No need to check fb_helper->dev->master in
drm_fb_helper_single_fb_probe(), restore_fbdev_mode() has the check.
Suggested-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
Documentation/gpu/todo.rst | 8 +++
drivers/gpu/drm/drm_auth.c | 20 +++++++
drivers/gpu/drm/drm_fb_helper.c | 102 ++++++++++++++++++--------------
drivers/gpu/drm/drm_internal.h | 2 +
4 files changed, 86 insertions(+), 46 deletions(-)
diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 06ccff9165d5..66f05f4e469f 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -281,6 +281,14 @@ it to use drm_mode_hsync() instead.
Contact: Sean Paul
+drm_fb_helper tasks
+-------------------
+
+- drm_fb_helper_restore_fbdev_mode_unlocked() should call restore_fbdev_mode()
+ not the _force variant so it can bail out if there is a master. But first
+ these igt tests need to be fixed: kms_fbcon_fbt@psr and
+ kms_fbcon_fbt@psr-suspend.
+
Core refactorings
=================
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c
index e88151b65c22..33aa459a1b8f 100644
--- a/drivers/gpu/drm/drm_auth.c
+++ b/drivers/gpu/drm/drm_auth.c
@@ -353,3 +353,23 @@ void drm_master_put(struct drm_master **master)
*master = NULL;
}
EXPORT_SYMBOL(drm_master_put);
+
+/* Used by drm_client and drm_fb_helper */
+bool drm_master_internal_acquire(struct drm_device *dev)
+{
+ mutex_lock(&dev->master_mutex);
+ if (dev->master) {
+ mutex_unlock(&dev->master_mutex);
+ return false;
+ }
+
+ return true;
+}
+EXPORT_SYMBOL(drm_master_internal_acquire);
+
+/* Used by drm_client and drm_fb_helper */
+void drm_master_internal_release(struct drm_device *dev)
+{
+ mutex_unlock(&dev->master_mutex);
+}
+EXPORT_SYMBOL(drm_master_internal_release);
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 45c5128a783b..6b4ce6060984 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -44,6 +44,7 @@
#include "drm_crtc_internal.h"
#include "drm_crtc_helper_internal.h"
+#include "drm_internal.h"
static bool drm_fbdev_emulation = true;
module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600);
@@ -509,7 +510,7 @@ static int restore_fbdev_mode_legacy(struct drm_fb_helper *fb_helper)
return ret;
}
-static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
+static int restore_fbdev_mode_force(struct drm_fb_helper *fb_helper)
{
struct drm_device *dev = fb_helper->dev;
@@ -519,6 +520,21 @@ static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
return restore_fbdev_mode_legacy(fb_helper);
}
+static int restore_fbdev_mode(struct drm_fb_helper *fb_helper)
+{
+ struct drm_device *dev = fb_helper->dev;
+ int ret;
+
+ if (!drm_master_internal_acquire(dev))
+ return -EBUSY;
+
+ ret = restore_fbdev_mode_force(fb_helper);
+
+ drm_master_internal_release(dev);
+
+ return ret;
+}
+
/**
* drm_fb_helper_restore_fbdev_mode_unlocked - restore fbdev configuration
* @fb_helper: driver-allocated fbdev helper, can be NULL
@@ -542,7 +558,17 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
return 0;
mutex_lock(&fb_helper->lock);
- ret = restore_fbdev_mode(fb_helper);
+ /*
+ * TODO:
+ * We should bail out here if there is a master by dropping _force.
+ * Currently these igt tests fail if we do that:
+ * - kms_fbcon_fbt@psr
+ * - kms_fbcon_fbt@psr-suspend
+ *
+ * So first these tests need to be fixed so they drop master or don't
+ * have an fd open.
+ */
+ ret = restore_fbdev_mode_force(fb_helper);
do_delayed = fb_helper->delayed_hotplug;
if (do_delayed)
@@ -556,34 +582,6 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
}
EXPORT_SYMBOL(drm_fb_helper_restore_fbdev_mode_unlocked);
-static bool drm_fb_helper_is_bound(struct drm_fb_helper *fb_helper)
-{
- struct drm_device *dev = fb_helper->dev;
- struct drm_crtc *crtc;
- int bound = 0, crtcs_bound = 0;
-
- /*
- * Sometimes user space wants everything disabled, so don't steal the
- * display if there's a master.
- */
- if (READ_ONCE(dev->master))
- return false;
-
- drm_for_each_crtc(crtc, dev) {
- drm_modeset_lock(&crtc->mutex, NULL);
- if (crtc->primary->fb)
- crtcs_bound++;
- if (crtc->primary->fb == fb_helper->fb)
- bound++;
- drm_modeset_unlock(&crtc->mutex);
- }
-
- if (bound < crtcs_bound)
- return false;
-
- return true;
-}
-
#ifdef CONFIG_MAGIC_SYSRQ
/*
* restore fbcon display for all kms driver's using this helper, used for sysrq
@@ -604,7 +602,7 @@ static bool drm_fb_helper_force_kernel_mode(void)
continue;
mutex_lock(&helper->lock);
- ret = restore_fbdev_mode(helper);
+ ret = restore_fbdev_mode_force(helper);
if (ret)
error = true;
mutex_unlock(&helper->lock);
@@ -663,20 +661,22 @@ static void dpms_legacy(struct drm_fb_helper *fb_helper, int dpms_mode)
static void drm_fb_helper_dpms(struct fb_info *info, int dpms_mode)
{
struct drm_fb_helper *fb_helper = info->par;
+ struct drm_device *dev = fb_helper->dev;
/*
* For each CRTC in this fb, turn the connectors on/off.
*/
mutex_lock(&fb_helper->lock);
- if (!drm_fb_helper_is_bound(fb_helper)) {
- mutex_unlock(&fb_helper->lock);
- return;
- }
+ if (!drm_master_internal_acquire(dev))
+ goto unlock;
- if (drm_drv_uses_atomic_modeset(fb_helper->dev))
+ if (drm_drv_uses_atomic_modeset(dev))
restore_fbdev_mode_atomic(fb_helper, dpms_mode == DRM_MODE_DPMS_ON);
else
dpms_legacy(fb_helper, dpms_mode);
+
+ drm_master_internal_release(dev);
+unlock:
mutex_unlock(&fb_helper->lock);
}
@@ -1509,6 +1509,7 @@ static int setcmap_atomic(struct fb_cmap *cmap, struct fb_info *info)
int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info)
{
struct drm_fb_helper *fb_helper = info->par;
+ struct drm_device *dev = fb_helper->dev;
int ret;
if (oops_in_progress)
@@ -1516,9 +1517,9 @@ int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info)
mutex_lock(&fb_helper->lock);
- if (!drm_fb_helper_is_bound(fb_helper)) {
+ if (!drm_master_internal_acquire(dev)) {
ret = -EBUSY;
- goto out;
+ goto unlock;
}
if (info->fix.visual == FB_VISUAL_TRUECOLOR)
@@ -1528,7 +1529,8 @@ int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info)
else
ret = setcmap_legacy(cmap, info);
-out:
+ drm_master_internal_release(dev);
+unlock:
mutex_unlock(&fb_helper->lock);
return ret;
@@ -1548,12 +1550,13 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
unsigned long arg)
{
struct drm_fb_helper *fb_helper = info->par;
+ struct drm_device *dev = fb_helper->dev;
struct drm_mode_set *mode_set;
struct drm_crtc *crtc;
int ret = 0;
mutex_lock(&fb_helper->lock);
- if (!drm_fb_helper_is_bound(fb_helper)) {
+ if (!drm_master_internal_acquire(dev)) {
ret = -EBUSY;
goto unlock;
}
@@ -1591,11 +1594,12 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
}
ret = 0;
- goto unlock;
+ break;
default:
ret = -ENOTTY;
}
+ drm_master_internal_release(dev);
unlock:
mutex_unlock(&fb_helper->lock);
return ret;
@@ -1847,15 +1851,18 @@ int drm_fb_helper_pan_display(struct fb_var_screeninfo *var,
return -EBUSY;
mutex_lock(&fb_helper->lock);
- if (!drm_fb_helper_is_bound(fb_helper)) {
- mutex_unlock(&fb_helper->lock);
- return -EBUSY;
+ if (!drm_master_internal_acquire(dev)) {
+ ret = -EBUSY;
+ goto unlock;
}
if (drm_drv_uses_atomic_modeset(dev))
ret = pan_display_atomic(var, info);
else
ret = pan_display_legacy(var, info);
+
+ drm_master_internal_release(dev);
+unlock:
mutex_unlock(&fb_helper->lock);
return ret;
@@ -2014,7 +2021,7 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
DRM_INFO("Cannot find any crtc or sizes\n");
/* First time: disable all crtc's.. */
- if (!fb_helper->deferred_setup && !READ_ONCE(fb_helper->dev->master))
+ if (!fb_helper->deferred_setup)
restore_fbdev_mode(fb_helper);
return -EAGAIN;
}
@@ -3029,6 +3036,7 @@ EXPORT_SYMBOL(drm_fb_helper_initial_config);
*/
int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
{
+ struct drm_device *dev = fb_helper->dev;
int err = 0;
if (!drm_fbdev_emulation || !fb_helper)
@@ -3041,12 +3049,14 @@ int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
return err;
}
- if (!fb_helper->fb || !drm_fb_helper_is_bound(fb_helper)) {
+ if (!fb_helper->fb || !drm_master_internal_acquire(dev)) {
fb_helper->delayed_hotplug = true;
mutex_unlock(&fb_helper->lock);
return err;
}
+ drm_master_internal_release(dev);
+
DRM_DEBUG_KMS("\n");
drm_setup_crtcs(fb_helper, fb_helper->fb->width, fb_helper->fb->height);
diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index e19ac7ca602d..e6281d9f9c87 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -93,6 +93,8 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
struct drm_file *file_priv);
int drm_master_open(struct drm_file *file_priv);
void drm_master_release(struct drm_file *file_priv);
+bool drm_master_internal_acquire(struct drm_device *dev);
+void drm_master_internal_release(struct drm_device *dev);
/* drm_sysfs.c */
extern struct class *drm_class;
--
2.20.1
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