在 2018/12/4 19:59, Christian König 写道: > Lockless container implementation similar to a dma_fence_array, but with > only two elements per node and automatic garbage collection. > > v2: properly document dma_fence_chain_for_each, add > dma_fence_chain_find_seqno, > drop prev reference during garbage collection if it's not a chain fence. > v3: use head and iterator for dma_fence_chain_for_each > > Signed-off-by: Christian König <[email protected]>
Reviewed-by: Chunming Zhou <[email protected]> > --- > drivers/dma-buf/Makefile | 3 +- > drivers/dma-buf/dma-fence-chain.c | 234 > ++++++++++++++++++++++++++++++++++++++ > include/linux/dma-fence-chain.h | 81 +++++++++++++ > 3 files changed, 317 insertions(+), 1 deletion(-) > create mode 100644 drivers/dma-buf/dma-fence-chain.c > create mode 100644 include/linux/dma-fence-chain.h > > diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile > index 0913a6ccab5a..1f006e083eb9 100644 > --- a/drivers/dma-buf/Makefile > +++ b/drivers/dma-buf/Makefile > @@ -1,4 +1,5 @@ > -obj-y := dma-buf.o dma-fence.o dma-fence-array.o reservation.o seqno-fence.o > +obj-y := dma-buf.o dma-fence.o dma-fence-array.o dma-fence-chain.o \ > + reservation.o seqno-fence.o > obj-$(CONFIG_SYNC_FILE) += sync_file.o > obj-$(CONFIG_SW_SYNC) += sw_sync.o sync_debug.o > obj-$(CONFIG_UDMABUF) += udmabuf.o > diff --git a/drivers/dma-buf/dma-fence-chain.c > b/drivers/dma-buf/dma-fence-chain.c > new file mode 100644 > index 000000000000..1ec234d66081 > --- /dev/null > +++ b/drivers/dma-buf/dma-fence-chain.c > @@ -0,0 +1,234 @@ > +/* > + * fence-chain: chain fences together in a timeline > + * > + * Copyright (C) 2018 Advanced Micro Devices, Inc. > + * Authors: > + * Christian König <[email protected]> > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms of the GNU General Public License version 2 as published > by > + * the Free Software Foundation. > + * > + * This program is distributed in the hope that it will be useful, but > WITHOUT > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for > + * more details. > + */ > + > +#include <linux/dma-fence-chain.h> > + > +static bool dma_fence_chain_enable_signaling(struct dma_fence *fence); > + > +/** > + * dma_fence_chain_get_prev - use RCU to get a reference to the previous > fence > + * @chain: chain node to get the previous node from > + * > + * Use dma_fence_get_rcu_safe to get a reference to the previous fence of the > + * chain node. > + */ > +static struct dma_fence *dma_fence_chain_get_prev(struct dma_fence_chain > *chain) > +{ > + struct dma_fence *prev; > + > + rcu_read_lock(); > + prev = dma_fence_get_rcu_safe(&chain->prev); > + rcu_read_unlock(); > + return prev; > +} > + > +/** > + * dma_fence_chain_walk - chain walking function > + * @fence: current chain node > + * > + * Walk the chain to the next node. Returns the next fence or NULL if we are > at > + * the end of the chain. Garbage collects chain nodes which are already > + * signaled. > + */ > +struct dma_fence *dma_fence_chain_walk(struct dma_fence *fence) > +{ > + struct dma_fence_chain *chain, *prev_chain; > + struct dma_fence *prev, *replacement, *tmp; > + > + chain = to_dma_fence_chain(fence); > + if (!chain) { > + dma_fence_put(fence); > + return NULL; > + } > + > + while ((prev = dma_fence_chain_get_prev(chain))) { > + > + prev_chain = to_dma_fence_chain(prev); > + if (prev_chain) { > + if (!dma_fence_is_signaled(prev_chain->fence)) > + break; > + > + replacement = dma_fence_chain_get_prev(prev_chain); > + } else { > + if (!dma_fence_is_signaled(prev)) > + break; > + > + replacement = NULL; > + } > + > + tmp = cmpxchg(&chain->prev, prev, replacement); > + if (tmp == prev) > + dma_fence_put(tmp); > + else > + dma_fence_put(replacement); > + dma_fence_put(prev); > + } > + > + dma_fence_put(fence); > + return prev; > +} > +EXPORT_SYMBOL(dma_fence_chain_walk); > + > +/** > + * dma_fence_chain_find_seqno - find fence chain node by seqno > + * @pfence: pointer to the chain node where to start > + * @seqno: the sequence number to search for > + * > + * Advance the fence pointer to the chain node which will signal this > sequence > + * number. If no sequence number is provided then this is a no-op. > + * > + * Returns EINVAL if the fence is not a chain node or the sequence number has > + * not yet advanced far enough. > + */ > +int dma_fence_chain_find_seqno(struct dma_fence **pfence, uint64_t seqno) > +{ > + struct dma_fence_chain *chain; > + > + if (!seqno) > + return 0; > + > + chain = to_dma_fence_chain(*pfence); > + if (!chain || chain->base.seqno < seqno) > + return -EINVAL; > + > + dma_fence_chain_for_each(*pfence, &chain->base) { > + if ((*pfence)->context != chain->base.context || > + to_dma_fence_chain(*pfence)->prev_seqno < seqno) > + break; > + } > + dma_fence_put(&chain->base); > + > + return 0; > +} > +EXPORT_SYMBOL(dma_fence_chain_find_seqno); > + > +static const char *dma_fence_chain_get_driver_name(struct dma_fence *fence) > +{ > + return "dma_fence_chain"; > +} > + > +static const char *dma_fence_chain_get_timeline_name(struct dma_fence *fence) > +{ > + return "unbound"; > +} > + > +static void dma_fence_chain_irq_work(struct irq_work *work) > +{ > + struct dma_fence_chain *chain; > + > + chain = container_of(work, typeof(*chain), work); > + > + /* Try to rearm the callback */ > + if (!dma_fence_chain_enable_signaling(&chain->base)) > + /* Ok, we are done. No more unsignaled fences left */ > + dma_fence_signal(&chain->base); > +} > + > +static void dma_fence_chain_cb(struct dma_fence *f, struct dma_fence_cb *cb) > +{ > + struct dma_fence_chain *chain; > + > + chain = container_of(cb, typeof(*chain), cb); > + irq_work_queue(&chain->work); > + dma_fence_put(f); > +} > + > +static bool dma_fence_chain_enable_signaling(struct dma_fence *fence) > +{ > + struct dma_fence_chain *head = to_dma_fence_chain(fence); > + > + dma_fence_chain_for_each(fence, &head->base) { > + struct dma_fence_chain *chain = to_dma_fence_chain(fence); > + struct dma_fence *f = chain ? chain->fence : fence; > + > + if (!dma_fence_add_callback(f, &head->cb, dma_fence_chain_cb)) > + return true; > + } > + return false; > +} > + > +static bool dma_fence_chain_signaled(struct dma_fence *fence) > +{ > + dma_fence_chain_for_each(fence, fence) { > + struct dma_fence_chain *chain = to_dma_fence_chain(fence); > + struct dma_fence *f = chain ? chain->fence : fence; > + > + if (!dma_fence_is_signaled(f)) { > + dma_fence_put(fence); > + return false; > + } > + } > + > + return true; > +} > + > +static void dma_fence_chain_release(struct dma_fence *fence) > +{ > + struct dma_fence_chain *chain = to_dma_fence_chain(fence); > + > + dma_fence_put(chain->prev); > + dma_fence_put(chain->fence); > + dma_fence_free(fence); > +} > + > +const struct dma_fence_ops dma_fence_chain_ops = { > + .get_driver_name = dma_fence_chain_get_driver_name, > + .get_timeline_name = dma_fence_chain_get_timeline_name, > + .enable_signaling = dma_fence_chain_enable_signaling, > + .signaled = dma_fence_chain_signaled, > + .release = dma_fence_chain_release, > +}; > +EXPORT_SYMBOL(dma_fence_chain_ops); > + > +/** > + * dma_fence_chain_init - initialize a fence chain > + * @chain: the chain node to initialize > + * @prev: the previous fence > + * @fence: the current fence > + * > + * Initialize a new chain node and either start a new chain or add the node > to > + * the existing chain of the previous fence. > + */ > +void dma_fence_chain_init(struct dma_fence_chain *chain, > + struct dma_fence *prev, > + struct dma_fence *fence, > + uint64_t seqno) > +{ > + struct dma_fence_chain *prev_chain = to_dma_fence_chain(prev); > + uint64_t context; > + > + spin_lock_init(&chain->lock); > + chain->prev = prev; > + chain->fence = fence; > + chain->prev_seqno = 0; > + init_irq_work(&chain->work, dma_fence_chain_irq_work); > + > + /* Try to reuse the context of the previous chain node. */ > + if (prev_chain && __dma_fence_is_later(seqno, prev->seqno)) { > + context = prev->context; > + chain->prev_seqno = prev->seqno; > + } else { > + context = dma_fence_context_alloc(1); > + /* Make sure that we always have a valid sequence number. */ > + if (prev_chain) > + seqno = max(prev->seqno, seqno); > + } > + > + dma_fence_init(&chain->base, &dma_fence_chain_ops, > + &chain->lock, context, seqno); > +} > +EXPORT_SYMBOL(dma_fence_chain_init); > diff --git a/include/linux/dma-fence-chain.h b/include/linux/dma-fence-chain.h > new file mode 100644 > index 000000000000..a5c2e8c6915c > --- /dev/null > +++ b/include/linux/dma-fence-chain.h > @@ -0,0 +1,81 @@ > +/* > + * fence-chain: chain fences together in a timeline > + * > + * Copyright (C) 2018 Advanced Micro Devices, Inc. > + * Authors: > + * Christian König <[email protected]> > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms of the GNU General Public License version 2 as published > by > + * the Free Software Foundation. > + * > + * This program is distributed in the hope that it will be useful, but > WITHOUT > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for > + * more details. > + */ > + > +#ifndef __LINUX_DMA_FENCE_CHAIN_H > +#define __LINUX_DMA_FENCE_CHAIN_H > + > +#include <linux/dma-fence.h> > +#include <linux/irq_work.h> > + > +/** > + * struct dma_fence_chain - fence to represent an node of a fence chain > + * @base: fence base class > + * @lock: spinlock for fence handling > + * @prev: previous fence of the chain > + * @prev_seqno: original previous seqno before garbage collection > + * @fence: encapsulated fence > + * @cb: callback structure for signaling > + * @work: irq work item for signaling > + */ > +struct dma_fence_chain { > + struct dma_fence base; > + spinlock_t lock; > + struct dma_fence *prev; > + u64 prev_seqno; > + struct dma_fence *fence; > + struct dma_fence_cb cb; > + struct irq_work work; > +}; > + > +extern const struct dma_fence_ops dma_fence_chain_ops; > + > +/** > + * to_dma_fence_chain - cast a fence to a dma_fence_chain > + * @fence: fence to cast to a dma_fence_array > + * > + * Returns NULL if the fence is not a dma_fence_chain, > + * or the dma_fence_chain otherwise. > + */ > +static inline struct dma_fence_chain * > +to_dma_fence_chain(struct dma_fence *fence) > +{ > + if (!fence || fence->ops != &dma_fence_chain_ops) > + return NULL; > + > + return container_of(fence, struct dma_fence_chain, base); > +} > + > +/** > + * dma_fence_chain_for_each - iterate over all fences in chain > + * @iter: current fence > + * @head: starting point > + * > + * Iterate over all fences in the chain. We keep a reference to the current > + * fence while inside the loop which must be dropped when breaking out. > + */ > +#define dma_fence_chain_for_each(iter, head) \ > + for (iter = dma_fence_get(head); iter; \ > + iter = dma_fence_chain_walk(head)) > + > +struct dma_fence *dma_fence_chain_walk(struct dma_fence *fence); > +int dma_fence_chain_find_seqno(struct dma_fence **pfence, uint64_t seqno); > +void dma_fence_chain_init(struct dma_fence_chain *chain, > + struct dma_fence *prev, > + struct dma_fence *fence, > + uint64_t seqno); > + > +#endif /* __LINUX_DMA_FENCE_CHAIN_H */ _______________________________________________ dri-devel mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/dri-devel
