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authorNoralf Trønnes <noralf@tronnes.org>2018-03-28 10:38:35 +0300
committerOleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>2018-03-29 13:19:20 +0300
commitbee330f3d67273a68dcb99f59480d59553c008b2 (patch)
treeabe48e9b35c199bf691b02efc40a5291f2391b40 /drivers/gpu/drm/drm_drv.c
parent790861cc34f872015806cef311d5c64cc3167a0d (diff)
downloadlinux-bee330f3d67273a68dcb99f59480d59553c008b2.tar.bz2
drm: Use srcu to protect drm_device.unplugged
Use srcu to protect drm_device.unplugged in a race free manner. Drivers can use drm_dev_enter()/drm_dev_exit() to protect and mark sections preventing access to device resources that are not available after the device is gone. Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Noralf Trønnes <noralf@tronnes.org> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> Tested-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> Cc: intel-gfx@lists.freedesktop.org Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/1522222715-11814-1-git-send-email-andr2000@gmail.com
Diffstat (limited to 'drivers/gpu/drm/drm_drv.c')
-rw-r--r--drivers/gpu/drm/drm_drv.c54
1 files changed, 49 insertions, 5 deletions
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index a1b9338736e3..32a83b41ab61 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -32,6 +32,7 @@
#include <linux/moduleparam.h>
#include <linux/mount.h>
#include <linux/slab.h>
+#include <linux/srcu.h>
#include <drm/drm_drv.h>
#include <drm/drmP.h>
@@ -75,6 +76,8 @@ static bool drm_core_init_complete = false;
static struct dentry *drm_debugfs_root;
+DEFINE_STATIC_SRCU(drm_unplug_srcu);
+
/*
* DRM Minors
* A DRM device can provide several char-dev interfaces on the DRM-Major. Each
@@ -318,18 +321,51 @@ void drm_put_dev(struct drm_device *dev)
}
EXPORT_SYMBOL(drm_put_dev);
-static void drm_device_set_unplugged(struct drm_device *dev)
+/**
+ * drm_dev_enter - Enter device critical section
+ * @dev: DRM device
+ * @idx: Pointer to index that will be passed to the matching drm_dev_exit()
+ *
+ * This function marks and protects the beginning of a section that should not
+ * be entered after the device has been unplugged. The section end is marked
+ * with drm_dev_exit(). Calls to this function can be nested.
+ *
+ * Returns:
+ * True if it is OK to enter the section, false otherwise.
+ */
+bool drm_dev_enter(struct drm_device *dev, int *idx)
+{
+ *idx = srcu_read_lock(&drm_unplug_srcu);
+
+ if (dev->unplugged) {
+ srcu_read_unlock(&drm_unplug_srcu, *idx);
+ return false;
+ }
+
+ return true;
+}
+EXPORT_SYMBOL(drm_dev_enter);
+
+/**
+ * drm_dev_exit - Exit device critical section
+ * @idx: index returned from drm_dev_enter()
+ *
+ * This function marks the end of a section that should not be entered after
+ * the device has been unplugged.
+ */
+void drm_dev_exit(int idx)
{
- smp_wmb();
- atomic_set(&dev->unplugged, 1);
+ srcu_read_unlock(&drm_unplug_srcu, idx);
}
+EXPORT_SYMBOL(drm_dev_exit);
/**
* drm_dev_unplug - unplug a DRM device
* @dev: DRM device
*
* This unplugs a hotpluggable DRM device, which makes it inaccessible to
- * userspace operations. Entry-points can use drm_dev_is_unplugged(). This
+ * userspace operations. Entry-points can use drm_dev_enter() and
+ * drm_dev_exit() to protect device resources in a race free manner. This
* essentially unregisters the device like drm_dev_unregister(), but can be
* called while there are still open users of @dev.
*/
@@ -338,10 +374,18 @@ void drm_dev_unplug(struct drm_device *dev)
drm_dev_unregister(dev);
mutex_lock(&drm_global_mutex);
- drm_device_set_unplugged(dev);
if (dev->open_count == 0)
drm_dev_put(dev);
mutex_unlock(&drm_global_mutex);
+
+ /*
+ * After synchronizing any critical read section is guaranteed to see
+ * the new value of ->unplugged, and any critical section which might
+ * still have seen the old value of ->unplugged is guaranteed to have
+ * finished.
+ */
+ dev->unplugged = true;
+ synchronize_srcu(&drm_unplug_srcu);
}
EXPORT_SYMBOL(drm_dev_unplug);