On Fri, Mar 11, 2022 at 12:02:43PM +0100, Christian König wrote:
> Add a general purpose helper to deep dive into dma_fence_chain/dma_fence_array
> structures and iterate over all the fences in them.
>
> This is useful when we need to flatten out all fences in those structures.
>
> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> ---
> Documentation/driver-api/dma-buf.rst | 6 +
> drivers/dma-buf/Makefile | 1 +
> drivers/dma-buf/selftests.h | 1 +
> drivers/dma-buf/st-dma-fence-unwrap.c | 279 ++++++++++++++++++++++++++
> include/linux/dma-fence-unwrap.h | 99 +++++++++
> 5 files changed, 386 insertions(+)
> create mode 100644 drivers/dma-buf/st-dma-fence-unwrap.c
> create mode 100644 include/linux/dma-fence-unwrap.h
>
> diff --git a/Documentation/driver-api/dma-buf.rst b/Documentation/driver-api/dma-buf.rst
> index 2cd7db82d9fe..7209500f08c8 100644
> --- a/Documentation/driver-api/dma-buf.rst
> +++ b/Documentation/driver-api/dma-buf.rst
> @@ -194,6 +194,12 @@ DMA Fence Chain
> .. kernel-doc:: include/linux/dma-fence-chain.h
> :internal:
>
> +DMA Fence unwrap
> +~~~~~~~~~~~~~~~~
> +
> +.. kernel-doc:: include/linux/dma-fence-unwrap.h
> + :internal:
> +
> DMA Fence uABI/Sync File
> ~~~~~~~~~~~~~~~~~~~~~~~~
>
> diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile
> index 511805dbeb75..4c9eb53ba3f8 100644
> --- a/drivers/dma-buf/Makefile
> +++ b/drivers/dma-buf/Makefile
> @@ -12,6 +12,7 @@ dmabuf_selftests-y := \
> selftest.o \
> st-dma-fence.o \
> st-dma-fence-chain.o \
> + st-dma-fence-unwrap.o \
> st-dma-resv.o
>
> obj-$(CONFIG_DMABUF_SELFTESTS) += dmabuf_selftests.o
> diff --git a/drivers/dma-buf/selftests.h b/drivers/dma-buf/selftests.h
> index 97d73aaa31da..851965867d9c 100644
> --- a/drivers/dma-buf/selftests.h
> +++ b/drivers/dma-buf/selftests.h
> @@ -12,4 +12,5 @@
> selftest(sanitycheck, __sanitycheck__) /* keep first (igt selfcheck) */
> selftest(dma_fence, dma_fence)
> selftest(dma_fence_chain, dma_fence_chain)
> +selftest(dma_fence_unwrap, dma_fence_unwrap)
> selftest(dma_resv, dma_resv)
> diff --git a/drivers/dma-buf/st-dma-fence-unwrap.c b/drivers/dma-buf/st-dma-fence-unwrap.c
> new file mode 100644
> index 000000000000..d821faaebe93
> --- /dev/null
> +++ b/drivers/dma-buf/st-dma-fence-unwrap.c
> @@ -0,0 +1,279 @@
> +// SPDX-License-Identifier: MIT
> +
> +/*
> + * Copyright (C) 2022 Advanced Micro Devices, Inc.
> + */
> +
> +#include <linux/dma-fence-unwrap.h>
> +#if 0
> +#include <linux/kernel.h>
> +#include <linux/kthread.h>
> +#include <linux/mm.h>
> +#include <linux/sched/signal.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +#include <linux/random.h>
> +#endif
> +
> +#include "selftest.h"
> +
> +#define CHAIN_SZ (4 << 10)
> +
> +static struct kmem_cache *slab_fences;
Your own slab feels a bit like overkill. kmalloc/kfree not good enough?
> +
> +static inline struct mock_fence {
> + struct dma_fence base;
> + spinlock_t lock;
> +} *to_mock_fence(struct dma_fence *f) {
> + return container_of(f, struct mock_fence, base);
> +}
> +
> +static const char *mock_name(struct dma_fence *f)
> +{
> + return "mock";
> +}
> +
> +static void mock_fence_release(struct dma_fence *f)
> +{
> + kmem_cache_free(slab_fences, to_mock_fence(f));
> +}
> +
> +static const struct dma_fence_ops mock_ops = {
> + .get_driver_name = mock_name,
> + .get_timeline_name = mock_name,
> + .release = mock_fence_release,
> +};
> +
> +static struct dma_fence *mock_fence(void)
> +{
> + struct mock_fence *f;
> +
> + f = kmem_cache_alloc(slab_fences, GFP_KERNEL);
> + if (!f)
> + return NULL;
> +
> + spin_lock_init(&f->lock);
> + dma_fence_init(&f->base, &mock_ops, &f->lock, 0, 0);
> +
> + return &f->base;
> +}
> +
> +static struct dma_fence *mock_array(unsigned int num_fences, ...)
> +{
> + struct dma_fence_array *array;
> + struct dma_fence **fences;
> + va_list valist;
> + int i;
> +
> + fences = kcalloc(num_fences, sizeof(*fences), GFP_KERNEL);
> + if (!fences)
> + return NULL;
> +
> + va_start(valist, num_fences);
> + for (i = 0; i < num_fences; ++i)
> + fences[i] = va_arg(valist, typeof(*fences));
> + va_end(valist);
> +
> + array = dma_fence_array_create(num_fences, fences,
> + dma_fence_context_alloc(1),
> + 1, false);
> + if (!array)
> + goto cleanup;
> + return &array->base;
> +
> +cleanup:
> + for (i = 0; i < num_fences; ++i)
> + dma_fence_put(fences[i]);
> + kfree(fences);
> + return NULL;
> +}
> +
> +static struct dma_fence *mock_chain(struct dma_fence *prev,
> + struct dma_fence *fence)
> +{
> + struct dma_fence_chain *f;
> +
> + f = dma_fence_chain_alloc();
> + if (!f) {
> + dma_fence_put(prev);
> + dma_fence_put(fence);
> + return NULL;
> + }
> +
> + dma_fence_chain_init(f, prev, fence, 1);
> + return &f->base;
> +}
> +
> +static int sanitycheck(void *arg)
> +{
> + struct dma_fence *f, *chain, *array;
> + int err = 0;
> +
> + f = mock_fence();
> + if (!f)
> + return -ENOMEM;
> +
> + array = mock_array(1, f);
> + if (!array)
> + return -ENOMEM;
> +
> + chain = mock_chain(NULL, array);
> + if (!chain)
> + return -ENOMEM;
> +
> + dma_fence_signal(f);
> + dma_fence_put(chain);
> + return err;
> +}
> +
> +static int unwrap_array(void *arg)
> +{
> + struct dma_fence *fence, *f1, *f2, *array;
> + struct dma_fence_unwrap iter;
> + int err = 0;
> +
> + f1 = mock_fence();
> + if (!f1)
> + return -ENOMEM;
> +
> + f2 = mock_fence();
> + if (!f2) {
> + dma_fence_put(f1);
> + return -ENOMEM;
> + }
> +
> + array = mock_array(2, f1, f2);
> + if (!array)
> + return -ENOMEM;
> +
> + dma_fence_unwrap_for_each(fence, &iter, array) {
> + if (fence == f1) {
> + f1 = NULL;
> + } else if (fence == f2) {
> + f2 = NULL;
> + } else {
> + pr_err("Unexpected fence!\n");
> + err = -EINVAL;
> + }
> + }
> +
> + if (f1 || f2) {
> + pr_err("Not all fences seen!\n");
> + err = -EINVAL;
> + }
> +
> + dma_fence_signal(f1);
> + dma_fence_signal(f2);
> + dma_fence_put(array);
> + return 0;
> +}
> +
> +static int unwrap_chain(void *arg)
> +{
> + struct dma_fence *fence, *f1, *f2, *chain;
> + struct dma_fence_unwrap iter;
> + int err = 0;
> +
> + f1 = mock_fence();
> + if (!f1)
> + return -ENOMEM;
> +
> + f2 = mock_fence();
> + if (!f2) {
> + dma_fence_put(f1);
> + return -ENOMEM;
> + }
> +
> + chain = mock_chain(f1, f2);
> + if (!chain)
> + return -ENOMEM;
> +
> + dma_fence_unwrap_for_each(fence, &iter, chain) {
> + if (fence == f1) {
> + f1 = NULL;
> + } else if (fence == f2) {
> + f2 = NULL;
> + } else {
> + pr_err("Unexpected fence!\n");
> + err = -EINVAL;
> + }
> + }
> +
> + if (f1 || f2) {
> + pr_err("Not all fences seen!\n");
> + err = -EINVAL;
> + }
> +
> + dma_fence_signal(f1);
> + dma_fence_signal(f2);
> + dma_fence_put(chain);
> + return 0;
> +}
> +
> +static int unwrap_chain_array(void *arg)
> +{
> + struct dma_fence *fence, *f1, *f2, *array, *chain;
> + struct dma_fence_unwrap iter;
> + int err = 0;
> +
> + f1 = mock_fence();
> + if (!f1)
> + return -ENOMEM;
> +
> + f2 = mock_fence();
> + if (!f2) {
> + dma_fence_put(f1);
> + return -ENOMEM;
> + }
> +
> + array = mock_array(2, f1, f2);
> + if (!array)
> + return -ENOMEM;
> +
> + chain = mock_chain(NULL, array);
> + if (!chain)
> + return -ENOMEM;
> +
> + dma_fence_unwrap_for_each(fence, &iter, chain) {
> + if (fence == f1) {
> + f1 = NULL;
> + } else if (fence == f2) {
> + f2 = NULL;
> + } else {
> + pr_err("Unexpected fence!\n");
> + err = -EINVAL;
> + }
> + }
> +
> + if (f1 || f2) {
> + pr_err("Not all fences seen!\n");
> + err = -EINVAL;
> + }
> +
> + dma_fence_signal(f1);
> + dma_fence_signal(f2);
> + dma_fence_put(chain);
> + return 0;
> +}
> +
> +int dma_fence_unwrap(void)
> +{
> + static const struct subtest tests[] = {
> + SUBTEST(sanitycheck),
> + SUBTEST(unwrap_array),
> + SUBTEST(unwrap_chain),
> + SUBTEST(unwrap_chain_array),
> + };
> + int ret;
> +
> + slab_fences = KMEM_CACHE(mock_fence,
> + SLAB_TYPESAFE_BY_RCU |
> + SLAB_HWCACHE_ALIGN);
> + if (!slab_fences)
> + return -ENOMEM;
> +
> + ret = subtests(tests, NULL);
> +
> + kmem_cache_destroy(slab_fences);
> + return ret;
> +}
> diff --git a/include/linux/dma-fence-unwrap.h b/include/linux/dma-fence-unwrap.h
> new file mode 100644
> index 000000000000..54963df00c98
> --- /dev/null
> +++ b/include/linux/dma-fence-unwrap.h
> @@ -0,0 +1,99 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * fence-chain: chain fences together in a timeline
> + *
> + * Copyright (C) 2022 Advanced Micro Devices, Inc.
> + * Authors:
> + * Christian König <christian.koenig@xxxxxxx>
> + */
> +
> +#ifndef __LINUX_DMA_FENCE_UNWRAP_H
> +#define __LINUX_DMA_FENCE_UNWRAP_H
> +
> +#include <linux/dma-fence-chain.h>
> +#include <linux/dma-fence-array.h>
> +
> +/**
> + * struct dma_fence_unwrap - cursor into the container structure
I think adding "This should be used together with
dma_fence_unwrap_for_each() iterator macro." would be nice here. I just
like links :-)
> + */
> +struct dma_fence_unwrap {
> + /**
> + * @chain: potential dma_fence_chain, but can be other fence as well
> + */
> + struct dma_fence *chain;
> + /**
> + * @array: potential dma_fence_array, but can be other fence as well
> + */
> + struct dma_fence *array;
> + /**
> + * @index: last returned index if @array is really a dma_fence_array
> + */
> + unsigned int index;
> +};
> +
> +/**
> + * dma_fence_unwrap_array - helper to unwrap dma_fence_arrays
> + * @cursor: cursor to initialize
> + *
> + * Helper function to unwrap dma_fence_array containers, don't touch directly.
> + * Use dma_fence_unwrap_first/next instead.
> + */
> +static inline struct dma_fence *
> +dma_fence_unwrap_array(struct dma_fence_unwrap * cursor)
Since this is a helper that no one should call I'd give it a __ prefix and
drop the kerneldoc. Documenting stuff that people shouldn't use is
confusing :-)
> +{
> + cursor->array = dma_fence_chain_contained(cursor->chain);
> + cursor->index = 0;
> + return dma_fence_array_first(cursor->array);
> +}
> +
> +/**
> + * dma_fence_unwrap_first - return the first fence from fence containers
> + * @head: the entrypoint into the containers
> + * @cursor: current position inside the containers
> + *
> + * Unwraps potential dma_fence_chain/dma_fence_array containers and return the
> + * first fence.
> + */
> +static inline struct dma_fence *
> +dma_fence_unwrap_first(struct dma_fence *head, struct dma_fence_unwrap *cursor)
> +{
> + cursor->chain = dma_fence_get(head);
> + return dma_fence_unwrap_array(cursor);
> +}
> +
> +/**
> + * dma_fence_unwrap_next - return the next fence from a fence containers
> + * @cursor: current position inside the containers
> + *
> + * Continue unwrapping the dma_fence_chain/dma_fence_array containers and return
> + * the next fence from them.
> + */
> +static inline struct dma_fence *
> +dma_fence_unwrap_next(struct dma_fence_unwrap *cursor)
> +{
> + struct dma_fence *tmp;
> +
> + ++cursor->index;
> + tmp = dma_fence_array_next(cursor->array, cursor->index);
> + if (tmp)
> + return tmp;
> +
> + cursor->chain = dma_fence_chain_walk(cursor->chain);
> + return dma_fence_unwrap_array(cursor);
> +}
> +
> +/**
> + * dma_fence_unwrap_for_each - iterate over all fences in containers
> + * @fence: current fence
> + * @cursor: current position inside the containers
> + * @head: starting point for the iterator
> + *
> + * Unwrap dma_fence_chain and dma_fence_array containers and deep dive into all
> + * potential fences in them. If @head is just a normal fence only that one is
> + * returned.
> + */
> +#define dma_fence_unwrap_for_each(fence, cursor, head) \
> + for (fence = dma_fence_unwrap_first(head, cursor); fence; \
> + fence = dma_fence_unwrap_next(cursor))
> +
> +#endif
I think it'd be really good to add a small paragraph to struct
dma_fence_chain that this macro and iterator should be used for walking
over all fences in a chain, including any fence arrays or anything like
that.
With the bikesheds addressed:
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> --
> 2.25.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
