[PATCH 1/2] dma-buf: add dma_fence_unwrap
Daniel Vetter
daniel at ffwll.ch
Fri Mar 25 10:07:27 UTC 2022
On Fri, Mar 25, 2022 at 11:03:54AM +0100, Daniel Vetter wrote:
> 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 at amd.com>
> > ---
> > 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:
Ok I forgot one bikeshed: I'd just include this in dma-fence-chain.h and
maybe go with the dma_fence_chain_unwrap_ prefix for everything. That
makes it even more clearer that the two are meant to go together. Plus ofc
the link from struct dma_fence_chain to this iterator in the docs too.
Or I'm just not understanding why you made this a separate thing?
-Daniel
> > +
> > 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 at amd.com>
> > + */
> > +
> > +#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 at ffwll.ch>
>
> > --
> > 2.25.1
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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