If the deadlock issue could be solved I don't see why we give up kfifo and switch to SPSC ...... -----Original Message----- From: amd-gfx [mailto:amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of Andrey Grodzovsky Sent: 2017å¹´10æ??20æ?¥ 21:32 To: amd-gfx at lists.freedesktop.org Cc: Grodzovsky, Andrey <Andrey.Grodzovsky at amd.com>; Koenig, Christian <Christian.Koenig at amd.com> Subject: [PATCH 2/3] drm/amdgpu: Add SPSC queue to scheduler. It is intended to sabstitute the bounded fifo we are currently using. Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky at amd.com> --- drivers/gpu/drm/amd/scheduler/spsc_queue.h | 120 +++++++++++++++++++++++++++++ 1 file changed, 120 insertions(+) create mode 100644 drivers/gpu/drm/amd/scheduler/spsc_queue.h diff --git a/drivers/gpu/drm/amd/scheduler/spsc_queue.h b/drivers/gpu/drm/amd/scheduler/spsc_queue.h new file mode 100644 index 0000000..a3394f1 --- /dev/null +++ b/drivers/gpu/drm/amd/scheduler/spsc_queue.h @@ -0,0 +1,120 @@ +/* + * Copyright 2017 Advanced Micro Devices, Inc. + * + * Permission is hereby granted, free of charge, to any person +obtaining a + * copy of this software and associated documentation files (the +"Software"), + * to deal in the Software without restriction, including without +limitation + * the rights to use, copy, modify, merge, publish, distribute, +sublicense, + * and/or sell copies of the Software, and to permit persons to whom +the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be +included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, +EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF +MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT +SHALL + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, +DAMAGES OR + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR +OTHERWISE, + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE +OR + * OTHER DEALINGS IN THE SOFTWARE. + * + */ + +#ifndef AMD_SCHEDULER_SPSC_QUEUE_H_ +#define AMD_SCHEDULER_SPSC_QUEUE_H_ + +#include <linux/atomic.h> + +/** SPSC lockless queue */ + +struct spsc_node { + + /* Stores spsc_node* */ + struct spsc_node *next; +}; + +struct spsc_queue { + + struct spsc_node *head; + + /* atomic pointer to struct spsc_node* */ + atomic_long_t tail; + + atomic_t job_count; +}; + +static inline void spsc_queue_init(struct spsc_queue *queue) { + queue->head = NULL; + atomic_long_set(&queue->tail, (long)&queue->head); + atomic_set(&queue->job_count, 0); +} + +static inline struct spsc_node *spsc_queue_peek(struct spsc_queue +*queue) { + return queue->head; +} + +static inline int spsc_queue_count(struct spsc_queue *queue) { + return atomic_read(&queue->job_count); } + +static inline bool spsc_queue_push(struct spsc_queue *queue, struct +spsc_node *node) { + struct spsc_node **tail; + + node->next = NULL; + + preempt_disable(); + + tail = (struct spsc_node **)atomic_long_xchg(&queue->tail, (long)&node->next); + WRITE_ONCE(*tail, node); + atomic_inc(&queue->job_count); + + /* + * In case of first element verify new node will be visible to the consumer + * thread when we ping the kernel thread that there is new work to do. + */ + smp_wmb(); + + preempt_enable(); + + return tail == &queue->head; +} + + +static inline struct spsc_node *spsc_queue_pop(struct spsc_queue +*queue) { + struct spsc_node *next, *node; + + /* Verify reading from memory and not the cache */ + smp_rmb(); + + node = READ_ONCE(queue->head); + + if (!node) + return NULL; + + next = READ_ONCE(node->next); + WRITE_ONCE(queue->head, next); + + if (unlikely(!next)) { + /* slowpath for the last element in the queue */ + + if (atomic_long_cmpxchg(&queue->tail, + (long)&node->next,(long) &queue->head) != (long)&node->next) { + /* Updating tail failed wait for new next to appear */ + do { + smp_rmb(); + }while (unlikely(!(queue->head = READ_ONCE(node->next)))); + } + } + + atomic_dec(&queue->job_count); + return node; +} + + + +#endif /* AMD_SCHEDULER_SPSC_QUEUE_H_ */ -- 2.7.4 _______________________________________________ amd-gfx mailing list amd-gfx at lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx
