From: Christian König ckoenig.leichtzumerken@gmail.com
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 v4: fix reference count in dma_fence_chain_enable_signaling v5: fix iteration when walking each chain node v6: add __rcu for member 'prev' of struct chain node v7: fix rcu warnings from kernel robot
Signed-off-by: Christian König christian.koenig@amd.com Cc: Lionel Landwerlin lionel.g.landwerlin@intel.com Reviewed-by: Lionel Landwerlin lionel.g.landwerlin@intel.com --- drivers/dma-buf/Makefile | 3 +- drivers/dma-buf/dma-fence-chain.c | 241 ++++++++++++++++++++++++++++++ include/linux/dma-fence-chain.h | 81 ++++++++++ 3 files changed, 324 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..c729f98a7bd3 --- /dev/null +++ b/drivers/dma-buf/dma-fence-chain.c @@ -0,0 +1,241 @@ +/* + * fence-chain: chain fences together in a timeline + * + * Copyright (C) 2018 Advanced Micro Devices, Inc. + * Authors: + * Christian König christian.koenig@amd.com + * + * 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((void **)&chain->prev, (void *)prev, (void *)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); + dma_fence_put(&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_get(&head->base); + 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; + + dma_fence_get(f); + if (!dma_fence_add_callback(f, &head->cb, dma_fence_chain_cb)) { + dma_fence_put(fence); + return true; + } + dma_fence_put(f); + } + dma_fence_put(&head->base); + 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(rcu_dereference_protected(chain->prev, true)); + 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); + rcu_assign_pointer(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..934a442db8ac --- /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 christian.koenig@amd.com + * + * 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 __rcu *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(iter)) + +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 */