[PATCH 03/51] drm: add managed resources tied to drm_device

[Daniel Vetter <daniel.vetter@ffwll.ch>]

We have lots of these. And the cleanup code tends to be of dubious
quality. The biggest wrong pattern is that developers use devm_, which
ties the release action to the underlying struct device, whereas
all the userspace visible stuff attached to a drm_device can long
outlive that one (e.g. after a hotunplug while userspace has open
files and mmap'ed buffers). Give people what they want, but with more
correctness.

Mostly copied from devres.c, with types adjusted to fit drm_device and
a few simplifications - I didn't (yet) copy over everything. Since
the types don't match code sharing looked like a hopeless endeavour.

For now it's only super simplified, no groups, you can't remove
actions (but kfree exists, we'll need that soon). Plus all specific to
drm_device ofc, including the logging. Which I didn't bother to make
compile-time optional, since none of the other drm logging is compile
time optional either.

One tricky bit here is the chicken&egg between allocating your
drm_device structure and initiliazing it with drm_dev_init. For
perfect onion unwinding we'd need to have the action to kfree the
allocation registered before drm_dev_init registers any of its own
release handlers. But drm_dev_init doesn't know where exactly the
drm_device is emebedded into the overall structure, and by the time it
returns it'll all be too late. And forcing drivers to be able clean up
everything except the one kzalloc is silly.

Work around this by having a very special final_kfree pointer. This
also avoids troubles with the list head possibly disappearing from
underneath us when we release all resources attached to the
drm_device.

v2: Do all the kerneldoc at the end, to avoid lots of fairly pointless
shuffling while getting everything into shape.

v3: Add static to add/del_dr (Neil)
Move typo fix to the right patch (Neil)

v4: Enforce contract for drmm_add_final_kfree:

Use ksize() to check that the drm_device is indeed contained somewhere
in the final kfree(). Because we need that or the entire managed
release logic blows up in a pile of use-after-frees. Motivated by a
discussion with Laurent.

v5: Review from Laurent:
- %zu instead of casting size_t
- header guards
- sorting of includes
- guarding of data assignment if we didn't allocate it for a NULL
  pointer
- delete spurious newline
- cast void* data parameter correctly in ->release call, no idea how
  this even worked before

v3: Review from Sam
- Add the kerneldoc for the managed sub-struct back in, even if it
  doesn't show up in the generated html somehow.
- Explain why __always_inline.
- Fix bisectability around the final kfree() in drm_dev_relase(). This
  is just interim code which will disappear again.
- Some whitespace polish.
- Add debug output when drmm_add_action or drmm_kmalloc fail.

Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Neil Armstrong <narmstrong@baylibre.com
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 Documentation/gpu/drm-internals.rst |   6 +
 drivers/gpu/drm/Makefile            |   3 +-
 drivers/gpu/drm/drm_drv.c           |  12 ++
 drivers/gpu/drm/drm_internal.h      |   3 +
 drivers/gpu/drm/drm_managed.c       | 186 ++++++++++++++++++++++++++++
 include/drm/drm_device.h            |  15 +++
 include/drm/drm_managed.h           |  30 +++++
 include/drm/drm_print.h             |   6 +
 8 files changed, 260 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/drm_managed.c
 create mode 100644 include/drm/drm_managed.h

diff --git a/Documentation/gpu/drm-internals.rst b/Documentation/gpu/drm-internals.rst
index a73320576ca9..a6b6145fda78 100644
--- a/Documentation/gpu/drm-internals.rst
+++ b/Documentation/gpu/drm-internals.rst
@@ -132,6 +132,12 @@ be unmapped; on many devices, the ROM address decoder is shared with
 other BARs, so leaving it mapped could cause undesired behaviour like
 hangs or memory corruption.
 
+Managed Resources
+-----------------
+
+.. kernel-doc:: drivers/gpu/drm/drm_managed.c
+   :doc: managed resources
+
 Bus-specific Device Registration and PCI Support
 ------------------------------------------------
 
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 7f72ef5e7811..183c60048307 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -17,7 +17,8 @@ drm-y       :=	drm_auth.o drm_cache.o \
 		drm_plane.o drm_color_mgmt.o drm_print.o \
 		drm_dumb_buffers.o drm_mode_config.o drm_vblank.o \
 		drm_syncobj.o drm_lease.o drm_writeback.o drm_client.o \
-		drm_client_modeset.o drm_atomic_uapi.o drm_hdcp.o
+		drm_client_modeset.o drm_atomic_uapi.o drm_hdcp.o \
+		drm_managed.o
 
 drm-$(CONFIG_DRM_LEGACY) += drm_legacy_misc.o drm_bufs.o drm_context.o drm_dma.o drm_scatter.o drm_lock.o
 drm-$(CONFIG_DRM_LIB_RANDOM) += lib/drm_random.o
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 9fcd6ab3c154..153050fc926c 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -629,6 +629,9 @@ int drm_dev_init(struct drm_device *dev,
 	dev->dev = get_device(parent);
 	dev->driver = driver;
 
+	INIT_LIST_HEAD(&dev->managed.resources);
+	spin_lock_init(&dev->managed.lock);
+
 	/* no per-device feature limits by default */
 	dev->driver_features = ~0u;
 
@@ -828,8 +831,17 @@ static void drm_dev_release(struct kref *ref)
 		dev->driver->release(dev);
 	} else {
 		drm_dev_fini(dev);
+	}
+
+	drm_managed_release(dev);
+
+	if (!dev->driver->release && !dev->managed.final_kfree) {
+		WARN_ON(!list_empty(&dev->managed.resources));
 		kfree(dev);
 	}
+
+	if (dev->managed.final_kfree)
+		kfree(dev->managed.final_kfree);
 }
 
 /**
diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index aeec2e68d772..8c2628dfc6c7 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -89,6 +89,9 @@ void drm_prime_remove_buf_handle_locked(struct drm_prime_file_private *prime_fpr
 struct drm_minor *drm_minor_acquire(unsigned int minor_id);
 void drm_minor_release(struct drm_minor *minor);
 
+/* drm_managed.c */
+void drm_managed_release(struct drm_device *dev);
+
 /* drm_vblank.c */
 void drm_vblank_disable_and_save(struct drm_device *dev, unsigned int pipe);
 void drm_vblank_cleanup(struct drm_device *dev);
diff --git a/drivers/gpu/drm/drm_managed.c b/drivers/gpu/drm/drm_managed.c
new file mode 100644
index 000000000000..57dc79fa90af
--- /dev/null
+++ b/drivers/gpu/drm/drm_managed.c
@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Intel
+ *
+ * Based on drivers/base/devres.c
+ */
+
+#include <drm/drm_managed.h>
+
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include <drm/drm_device.h>
+#include <drm/drm_print.h>
+
+/**
+ * DOC: managed resources
+ *
+ * Inspired by struct &device managed resources, but tied to the lifetime of
+ * struct &drm_device, which can outlive the underlying physical device, usually
+ * when userspace has some open files and other handles to resources still open.
+ */
+struct drmres_node {
+	struct list_head	entry;
+	drmres_release_t	release;
+	const char		*name;
+	size_t			size;
+};
+
+struct drmres {
+	struct drmres_node		node;
+	/*
+	 * Some archs want to perform DMA into kmalloc caches
+	 * and need a guaranteed alignment larger than
+	 * the alignment of a 64-bit integer.
+	 * Thus we use ARCH_KMALLOC_MINALIGN here and get exactly the same
+	 * buffer alignment as if it was allocated by plain kmalloc().
+	 */
+	u8 __aligned(ARCH_KMALLOC_MINALIGN) data[];
+};
+
+void drm_managed_release(struct drm_device *dev)
+{
+	struct drmres *dr, *tmp;
+
+	drm_dbg_drmres(dev, "drmres release begin\n");
+	list_for_each_entry_safe(dr, tmp, &dev->managed.resources, node.entry) {
+		drm_dbg_drmres(dev, "REL %p %s (%zu bytes)\n",
+			       dr, dr->node.name, dr->node.size);
+
+		if (dr->node.release)
+			dr->node.release(dev, dr->node.size ? *(void **)&dr->data : NULL);
+
+		list_del(&dr->node.entry);
+		kfree(dr);
+	}
+	drm_dbg_drmres(dev, "drmres release end\n");
+}
+
+/*
+ * Always inline so that kmallc_track_caller tracks the actual interesting
+ * caller outside of drm_managed.c.
+ */
+static __always_inline struct drmres * alloc_dr(drmres_release_t release,
+						size_t size, gfp_t gfp, int nid)
+{
+	size_t tot_size;
+	struct drmres *dr;
+
+	/* We must catch any near-SIZE_MAX cases that could overflow. */
+	if (unlikely(check_add_overflow(sizeof(*dr), size, &tot_size)))
+		return NULL;
+
+	dr = kmalloc_node_track_caller(tot_size, gfp, nid);
+	if (unlikely(!dr))
+		return NULL;
+
+	memset(dr, 0, offsetof(struct drmres, data));
+
+	INIT_LIST_HEAD(&dr->node.entry);
+	dr->node.release = release;
+	dr->node.size = size;
+
+	return dr;
+}
+
+static void del_dr(struct drm_device *dev, struct drmres *dr)
+{
+	list_del_init(&dr->node.entry);
+
+	drm_dbg_drmres(dev, "DEL %p %s (%lu bytes)\n",
+		       dr, dr->node.name, (unsigned long) dr->node.size);
+}
+
+static void add_dr(struct drm_device *dev, struct drmres *dr)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->managed.lock, flags);
+	list_add(&dr->node.entry, &dev->managed.resources);
+	spin_unlock_irqrestore(&dev->managed.lock, flags);
+
+	drm_dbg_drmres(dev, "ADD %p %s (%lu bytes)\n",
+		       dr, dr->node.name, (unsigned long) dr->node.size);
+}
+
+void drmm_add_final_kfree(struct drm_device *dev, void *parent)
+{
+	WARN_ON(dev->managed.final_kfree);
+	WARN_ON(dev < (struct drm_device *) parent);
+	WARN_ON(dev + 1 >= (struct drm_device *) (parent + ksize(parent)));
+	dev->managed.final_kfree = parent;
+}
+EXPORT_SYMBOL(drmm_add_final_kfree);
+
+int __drmm_add_action(struct drm_device *dev,
+		      drmres_release_t action,
+		      void *data, const char *name)
+{
+	struct drmres *dr;
+	void **void_ptr;
+
+	dr = alloc_dr(action, data ? sizeof(void*) : 0,
+		      GFP_KERNEL | __GFP_ZERO,
+		      dev_to_node(dev->dev));
+	if (!dr) {
+		drm_dbg_drmres(dev, "failed to add action %s for %p\n",
+			       name, data);
+		return -ENOMEM;
+	}
+
+	dr->node.name = name;
+	if (data) {
+		void_ptr = (void **)&dr->data;
+		*void_ptr = data;
+	}
+
+	add_dr(dev, dr);
+
+	return 0;
+}
+EXPORT_SYMBOL(__drmm_add_action);
+
+void *drmm_kmalloc(struct drm_device *dev, size_t size, gfp_t gfp)
+{
+	struct drmres *dr;
+
+	dr = alloc_dr(NULL, size, gfp, dev_to_node(dev->dev));
+	if (!dr) {
+		drm_dbg_drmres(dev, "failed to allocate %zu bytes, %u flags\n",
+			       size, gfp);
+		return NULL;
+	}
+	dr->node.name = "kmalloc";
+
+	add_dr(dev, dr);
+
+	return dr->data;
+}
+EXPORT_SYMBOL(drmm_kmalloc);
+
+void drmm_kfree(struct drm_device *dev, void *data)
+{
+	struct drmres *dr_match = NULL, *dr;
+	unsigned long flags;
+
+	if (!data)
+		return;
+
+	spin_lock_irqsave(&dev->managed.lock, flags);
+	list_for_each_entry(dr, &dev->managed.resources, node.entry) {
+		if (dr->data == data) {
+			dr_match = dr;
+			del_dr(dev, dr_match);
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&dev->managed.lock, flags);
+
+	if (WARN_ON(!dr_match))
+		return;
+
+	kfree(dr_match);
+}
+EXPORT_SYMBOL(drmm_kfree);
diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
index bb60a949f416..d39132b477dd 100644
--- a/include/drm/drm_device.h
+++ b/include/drm/drm_device.h
@@ -67,6 +67,21 @@ struct drm_device {
 	/** @dev: Device structure of bus-device */
 	struct device *dev;
 
+	/**
+	 * @managed:
+	 *
+	 * Managed resources linked to the lifetime of this &drm_device as
+	 * tracked by @ref.
+	 */
+	struct {
+		/** @managed.resources: managed resources list */
+		struct list_head resources;
+		/** @managed.final_kfree: pointer for final kfree() call */
+		void *final_kfree;
+		/** @managed.lock: protects @managed.resources */
+		spinlock_t lock;
+	} managed;
+
 	/** @driver: DRM driver managing the device */
 	struct drm_driver *driver;
 
diff --git a/include/drm/drm_managed.h b/include/drm/drm_managed.h
new file mode 100644
index 000000000000..7b5df7d09b19
--- /dev/null
+++ b/include/drm/drm_managed.h
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef _DRM_MANAGED_H_
+#define _DRM_MANAGED_H_
+
+#include <linux/gfp.h>
+#include <linux/types.h>
+
+struct drm_device;
+
+typedef void (*drmres_release_t)(struct drm_device *dev, void *res);
+
+#define drmm_add_action(dev, action, data) \
+	__drmm_add_action(dev, action, data, #action)
+
+int __must_check __drmm_add_action(struct drm_device *dev,
+				   drmres_release_t action,
+				   void *data, const char *name);
+
+void drmm_add_final_kfree(struct drm_device *dev, void *parent);
+
+void *drmm_kmalloc(struct drm_device *dev, size_t size, gfp_t gfp) __malloc;
+static inline void *drmm_kzalloc(struct drm_device *dev, size_t size, gfp_t gfp)
+{
+	return drmm_kmalloc(dev, size, gfp | __GFP_ZERO);
+}
+
+void drmm_kfree(struct drm_device *dev, void *data);
+
+#endif
diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h
index ca7cee8e728a..1c9417430d08 100644
--- a/include/drm/drm_print.h
+++ b/include/drm/drm_print.h
@@ -313,6 +313,10 @@ enum drm_debug_category {
 	 * @DRM_UT_DP: Used in the DP code.
 	 */
 	DRM_UT_DP		= 0x100,
+	/**
+	 * @DRM_UT_DRMRES: Used in the drm managed resources code.
+	 */
+	DRM_UT_DRMRES		= 0x200,
 };
 
 static inline bool drm_debug_enabled(enum drm_debug_category category)
@@ -442,6 +446,8 @@ void drm_dev_dbg(const struct device *dev, enum drm_debug_category category,
 	drm_dev_dbg((drm)->dev, DRM_UT_LEASE, fmt, ##__VA_ARGS__)
 #define drm_dbg_dp(drm, fmt, ...)					\
 	drm_dev_dbg((drm)->dev, DRM_UT_DP, fmt, ##__VA_ARGS__)
+#define drm_dbg_drmres(drm, fmt, ...)					\
+	drm_dev_dbg((drm)->dev, DRM_UT_DRMRES, fmt, ##__VA_ARGS__)
 
 
 /*
-- 
2.24.1

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