Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 413 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_modeset_lock.c b/drivers/gpu/drm/drm_modeset_lock.c
new file mode 100644
index 000000000..8a5100685
--- /dev/null
+++ b/drivers/gpu/drm/drm_modeset_lock.c
@@ -0,0 +1,413 @@
+/*
+ * Copyright (C) 2014 Red Hat
+ * Author: Rob Clark <robdclark@gmail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <drm/drmP.h>
+#include <drm/drm_crtc.h>
+#include <drm/drm_modeset_lock.h>
+
+/**
+ * DOC: kms locking
+ *
+ * As KMS moves toward more fine grained locking, and atomic ioctl where
+ * userspace can indirectly control locking order, it becomes necessary
+ * to use &ww_mutex and acquire-contexts to avoid deadlocks.  But because
+ * the locking is more distributed around the driver code, we want a bit
+ * of extra utility/tracking out of our acquire-ctx.  This is provided
+ * by &struct drm_modeset_lock and &struct drm_modeset_acquire_ctx.
+ *
+ * For basic principles of &ww_mutex, see: Documentation/locking/ww-mutex-design.txt
+ *
+ * The basic usage pattern is to::
+ *
+ *     drm_modeset_acquire_init(ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE)
+ *     retry:
+ *     foreach (lock in random_ordered_set_of_locks) {
+ *         ret = drm_modeset_lock(lock, ctx)
+ *         if (ret == -EDEADLK) {
+ *             ret = drm_modeset_backoff(ctx);
+ *             if (!ret)
+ *                 goto retry;
+ *         }
+ *         if (ret)
+ *             goto out;
+ *     }
+ *     ... do stuff ...
+ *     out:
+ *     drm_modeset_drop_locks(ctx);
+ *     drm_modeset_acquire_fini(ctx);
+ *
+ * If all that is needed is a single modeset lock, then the &struct
+ * drm_modeset_acquire_ctx is not needed and the locking can be simplified
+ * by passing a NULL instead of ctx in the drm_modeset_lock() call or
+ * calling  drm_modeset_lock_single_interruptible(). To unlock afterwards
+ * call drm_modeset_unlock().
+ *
+ * On top of these per-object locks using &ww_mutex there's also an overall
+ * &drm_mode_config.mutex, for protecting everything else. Mostly this means
+ * probe state of connectors, and preventing hotplug add/removal of connectors.
+ *
+ * Finally there's a bunch of dedicated locks to protect drm core internal
+ * lists and lookup data structures.
+ */
+
+static DEFINE_WW_CLASS(crtc_ww_class);
+
+/**
+ * drm_modeset_lock_all - take all modeset locks
+ * @dev: DRM device
+ *
+ * This function takes all modeset locks, suitable where a more fine-grained
+ * scheme isn't (yet) implemented. Locks must be dropped by calling the
+ * drm_modeset_unlock_all() function.
+ *
+ * This function is deprecated. It allocates a lock acquisition context and
+ * stores it in &drm_device.mode_config. This facilitate conversion of
+ * existing code because it removes the need to manually deal with the
+ * acquisition context, but it is also brittle because the context is global
+ * and care must be taken not to nest calls. New code should use the
+ * drm_modeset_lock_all_ctx() function and pass in the context explicitly.
+ */
+void drm_modeset_lock_all(struct drm_device *dev)
+{
+	struct drm_mode_config *config = &dev->mode_config;
+	struct drm_modeset_acquire_ctx *ctx;
+	int ret;
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL | __GFP_NOFAIL);
+	if (WARN_ON(!ctx))
+		return;
+
+	mutex_lock(&config->mutex);
+
+	drm_modeset_acquire_init(ctx, 0);
+
+retry:
+	ret = drm_modeset_lock_all_ctx(dev, ctx);
+	if (ret < 0) {
+		if (ret == -EDEADLK) {
+			drm_modeset_backoff(ctx);
+			goto retry;
+		}
+
+		drm_modeset_acquire_fini(ctx);
+		kfree(ctx);
+		return;
+	}
+	ww_acquire_done(&ctx->ww_ctx);
+
+	WARN_ON(config->acquire_ctx);
+
+	/*
+	 * We hold the locks now, so it is safe to stash the acquisition
+	 * context for drm_modeset_unlock_all().
+	 */
+	config->acquire_ctx = ctx;
+
+	drm_warn_on_modeset_not_all_locked(dev);
+}
+EXPORT_SYMBOL(drm_modeset_lock_all);
+
+/**
+ * drm_modeset_unlock_all - drop all modeset locks
+ * @dev: DRM device
+ *
+ * This function drops all modeset locks taken by a previous call to the
+ * drm_modeset_lock_all() function.
+ *
+ * This function is deprecated. It uses the lock acquisition context stored
+ * in &drm_device.mode_config. This facilitates conversion of existing
+ * code because it removes the need to manually deal with the acquisition
+ * context, but it is also brittle because the context is global and care must
+ * be taken not to nest calls. New code should pass the acquisition context
+ * directly to the drm_modeset_drop_locks() function.
+ */
+void drm_modeset_unlock_all(struct drm_device *dev)
+{
+	struct drm_mode_config *config = &dev->mode_config;
+	struct drm_modeset_acquire_ctx *ctx = config->acquire_ctx;
+
+	if (WARN_ON(!ctx))
+		return;
+
+	config->acquire_ctx = NULL;
+	drm_modeset_drop_locks(ctx);
+	drm_modeset_acquire_fini(ctx);
+
+	kfree(ctx);
+
+	mutex_unlock(&dev->mode_config.mutex);
+}
+EXPORT_SYMBOL(drm_modeset_unlock_all);
+
+/**
+ * drm_warn_on_modeset_not_all_locked - check that all modeset locks are locked
+ * @dev: device
+ *
+ * Useful as a debug assert.
+ */
+void drm_warn_on_modeset_not_all_locked(struct drm_device *dev)
+{
+	struct drm_crtc *crtc;
+
+	/* Locking is currently fubar in the panic handler. */
+	if (oops_in_progress)
+		return;
+
+	drm_for_each_crtc(crtc, dev)
+		WARN_ON(!drm_modeset_is_locked(&crtc->mutex));
+
+	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
+	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
+}
+EXPORT_SYMBOL(drm_warn_on_modeset_not_all_locked);
+
+/**
+ * drm_modeset_acquire_init - initialize acquire context
+ * @ctx: the acquire context
+ * @flags: 0 or %DRM_MODESET_ACQUIRE_INTERRUPTIBLE
+ *
+ * When passing %DRM_MODESET_ACQUIRE_INTERRUPTIBLE to @flags,
+ * all calls to drm_modeset_lock() will perform an interruptible
+ * wait.
+ */
+void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
+		uint32_t flags)
+{
+	memset(ctx, 0, sizeof(*ctx));
+	ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class);
+	INIT_LIST_HEAD(&ctx->locked);
+
+	if (flags & DRM_MODESET_ACQUIRE_INTERRUPTIBLE)
+		ctx->interruptible = true;
+}
+EXPORT_SYMBOL(drm_modeset_acquire_init);
+
+/**
+ * drm_modeset_acquire_fini - cleanup acquire context
+ * @ctx: the acquire context
+ */
+void drm_modeset_acquire_fini(struct drm_modeset_acquire_ctx *ctx)
+{
+	ww_acquire_fini(&ctx->ww_ctx);
+}
+EXPORT_SYMBOL(drm_modeset_acquire_fini);
+
+/**
+ * drm_modeset_drop_locks - drop all locks
+ * @ctx: the acquire context
+ *
+ * Drop all locks currently held against this acquire context.
+ */
+void drm_modeset_drop_locks(struct drm_modeset_acquire_ctx *ctx)
+{
+	WARN_ON(ctx->contended);
+	while (!list_empty(&ctx->locked)) {
+		struct drm_modeset_lock *lock;
+
+		lock = list_first_entry(&ctx->locked,
+				struct drm_modeset_lock, head);
+
+		drm_modeset_unlock(lock);
+	}
+}
+EXPORT_SYMBOL(drm_modeset_drop_locks);
+
+static inline int modeset_lock(struct drm_modeset_lock *lock,
+		struct drm_modeset_acquire_ctx *ctx,
+		bool interruptible, bool slow)
+{
+	int ret;
+
+	WARN_ON(ctx->contended);
+
+	if (ctx->trylock_only) {
+		lockdep_assert_held(&ctx->ww_ctx);
+
+		if (!ww_mutex_trylock(&lock->mutex))
+			return -EBUSY;
+		else
+			return 0;
+	} else if (interruptible && slow) {
+		ret = ww_mutex_lock_slow_interruptible(&lock->mutex, &ctx->ww_ctx);
+	} else if (interruptible) {
+		ret = ww_mutex_lock_interruptible(&lock->mutex, &ctx->ww_ctx);
+	} else if (slow) {
+		ww_mutex_lock_slow(&lock->mutex, &ctx->ww_ctx);
+		ret = 0;
+	} else {
+		ret = ww_mutex_lock(&lock->mutex, &ctx->ww_ctx);
+	}
+	if (!ret) {
+		WARN_ON(!list_empty(&lock->head));
+		list_add(&lock->head, &ctx->locked);
+	} else if (ret == -EALREADY) {
+		/* we already hold the lock.. this is fine.  For atomic
+		 * we will need to be able to drm_modeset_lock() things
+		 * without having to keep track of what is already locked
+		 * or not.
+		 */
+		ret = 0;
+	} else if (ret == -EDEADLK) {
+		ctx->contended = lock;
+	}
+
+	return ret;
+}
+
+/**
+ * drm_modeset_backoff - deadlock avoidance backoff
+ * @ctx: the acquire context
+ *
+ * If deadlock is detected (ie. drm_modeset_lock() returns -EDEADLK),
+ * you must call this function to drop all currently held locks and
+ * block until the contended lock becomes available.
+ *
+ * This function returns 0 on success, or -ERESTARTSYS if this context
+ * is initialized with %DRM_MODESET_ACQUIRE_INTERRUPTIBLE and the
+ * wait has been interrupted.
+ */
+int drm_modeset_backoff(struct drm_modeset_acquire_ctx *ctx)
+{
+	struct drm_modeset_lock *contended = ctx->contended;
+
+	ctx->contended = NULL;
+
+	if (WARN_ON(!contended))
+		return 0;
+
+	drm_modeset_drop_locks(ctx);
+
+	return modeset_lock(contended, ctx, ctx->interruptible, true);
+}
+EXPORT_SYMBOL(drm_modeset_backoff);
+
+/**
+ * drm_modeset_lock_init - initialize lock
+ * @lock: lock to init
+ */
+void drm_modeset_lock_init(struct drm_modeset_lock *lock)
+{
+	ww_mutex_init(&lock->mutex, &crtc_ww_class);
+	INIT_LIST_HEAD(&lock->head);
+}
+EXPORT_SYMBOL(drm_modeset_lock_init);
+
+/**
+ * drm_modeset_lock - take modeset lock
+ * @lock: lock to take
+ * @ctx: acquire ctx
+ *
+ * If @ctx is not NULL, then its ww acquire context is used and the
+ * lock will be tracked by the context and can be released by calling
+ * drm_modeset_drop_locks().  If -EDEADLK is returned, this means a
+ * deadlock scenario has been detected and it is an error to attempt
+ * to take any more locks without first calling drm_modeset_backoff().
+ *
+ * If the @ctx is not NULL and initialized with
+ * %DRM_MODESET_ACQUIRE_INTERRUPTIBLE, this function will fail with
+ * -ERESTARTSYS when interrupted.
+ *
+ * If @ctx is NULL then the function call behaves like a normal,
+ * uninterruptible non-nesting mutex_lock() call.
+ */
+int drm_modeset_lock(struct drm_modeset_lock *lock,
+		struct drm_modeset_acquire_ctx *ctx)
+{
+	if (ctx)
+		return modeset_lock(lock, ctx, ctx->interruptible, false);
+
+	ww_mutex_lock(&lock->mutex, NULL);
+	return 0;
+}
+EXPORT_SYMBOL(drm_modeset_lock);
+
+/**
+ * drm_modeset_lock_single_interruptible - take a single modeset lock
+ * @lock: lock to take
+ *
+ * This function behaves as drm_modeset_lock() with a NULL context,
+ * but performs interruptible waits.
+ *
+ * This function returns 0 on success, or -ERESTARTSYS when interrupted.
+ */
+int drm_modeset_lock_single_interruptible(struct drm_modeset_lock *lock)
+{
+	return ww_mutex_lock_interruptible(&lock->mutex, NULL);
+}
+EXPORT_SYMBOL(drm_modeset_lock_single_interruptible);
+
+/**
+ * drm_modeset_unlock - drop modeset lock
+ * @lock: lock to release
+ */
+void drm_modeset_unlock(struct drm_modeset_lock *lock)
+{
+	list_del_init(&lock->head);
+	ww_mutex_unlock(&lock->mutex);
+}
+EXPORT_SYMBOL(drm_modeset_unlock);
+
+/**
+ * drm_modeset_lock_all_ctx - take all modeset locks
+ * @dev: DRM device
+ * @ctx: lock acquisition context
+ *
+ * This function takes all modeset locks, suitable where a more fine-grained
+ * scheme isn't (yet) implemented.
+ *
+ * Unlike drm_modeset_lock_all(), it doesn't take the &drm_mode_config.mutex
+ * since that lock isn't required for modeset state changes. Callers which
+ * need to grab that lock too need to do so outside of the acquire context
+ * @ctx.
+ *
+ * Locks acquired with this function should be released by calling the
+ * drm_modeset_drop_locks() function on @ctx.
+ *
+ * Returns: 0 on success or a negative error-code on failure.
+ */
+int drm_modeset_lock_all_ctx(struct drm_device *dev,
+			     struct drm_modeset_acquire_ctx *ctx)
+{
+	struct drm_crtc *crtc;
+	struct drm_plane *plane;
+	int ret;
+
+	ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
+	if (ret)
+		return ret;
+
+	drm_for_each_crtc(crtc, dev) {
+		ret = drm_modeset_lock(&crtc->mutex, ctx);
+		if (ret)
+			return ret;
+	}
+
+	drm_for_each_plane(plane, dev) {
+		ret = drm_modeset_lock(&plane->mutex, ctx);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_modeset_lock_all_ctx);