drm: Use srcu to protect drm_device.unplugged (bee330f3) · Commits · 戴 / test

drivers/gpu/drm/drm_drv.c

+49 −5

Original line number	Diff line number	Diff line
		@@ -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);

include/drm/drm_device.h

+8 −1

Original line number	Diff line number	Diff line
		@@ -46,7 +46,14 @@ struct drm_device {
		/* currently active master for this device. Protected by master_mutex */
		struct drm_master *master;

		atomic_t unplugged; /*< Flag whether dev is dead /
		/**
		* @unplugged:
		*
		* Flag to tell if the device has been unplugged.
		* See drm_dev_enter() and drm_dev_is_unplugged().
		*/
		bool unplugged;

		struct inode anon_inode; /< inode for private address-space /
		char unique; /< unique name of the device /
		/@} /

include/drm/drm_drv.h

+11 −4

Original line number	Diff line number	Diff line
		@@ -623,6 +623,8 @@ void drm_dev_get(struct drm_device *dev);
		void drm_dev_put(struct drm_device *dev);
		void drm_dev_unref(struct drm_device *dev);
		void drm_put_dev(struct drm_device *dev);
		bool drm_dev_enter(struct drm_device dev, int idx);
		void drm_dev_exit(int idx);
		void drm_dev_unplug(struct drm_device *dev);

		/**
		@@ -634,11 +636,16 @@ void drm_dev_unplug(struct drm_device *dev);
		* unplugged, these two functions guarantee that any store before calling
		* drm_dev_unplug() is visible to callers of this function after it completes
		*/
		static inline int drm_dev_is_unplugged(struct drm_device *dev)
		static inline bool drm_dev_is_unplugged(struct drm_device *dev)
		{
		int ret = atomic_read(&dev->unplugged);
		smp_rmb();
		return ret;
		int idx;

		if (drm_dev_enter(dev, &idx)) {
		drm_dev_exit(idx);
		return false;
		}

		return true;
		}

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