3340202f59
This commit adds support for a lock-free (linked list based) stack to the stack API. This behavior is selected through a new rte_stack_create() flag, RTE_STACK_F_LF. The stack consists of a linked list of elements, each containing a data pointer and a next pointer, and an atomic stack depth counter. The lock-free push operation enqueues a linked list of pointers by pointing the tail of the list to the current stack head, and using a CAS to swing the stack head pointer to the head of the list. The operation retries if it is unsuccessful (i.e. the list changed between reading the head and modifying it), else it adjusts the stack length and returns. The lock-free pop operation first reserves num elements by adjusting the stack length, to ensure the dequeue operation will succeed without blocking. It then dequeues pointers by walking the list -- starting from the head -- then swinging the head pointer (using a CAS as well). While walking the list, the data pointers are recorded in an object table. This algorithm stack uses a 128-bit compare-and-swap instruction, which atomically updates the stack top pointer and a modification counter, to protect against the ABA problem. The linked list elements themselves are maintained in a lock-free LIFO list, and are allocated before stack pushes and freed after stack pops. Since the stack has a fixed maximum depth, these elements do not need to be dynamically created. Signed-off-by: Gage Eads <gage.eads@intel.com> Reviewed-by: Olivier Matz <olivier.matz@6wind.com> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
32 lines
676 B
C
32 lines
676 B
C
/* SPDX-License-Identifier: BSD-3-Clause
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* Copyright(c) 2019 Intel Corporation
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*/
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#include "rte_stack.h"
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void
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rte_stack_lf_init(struct rte_stack *s, unsigned int count)
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{
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struct rte_stack_lf_elem *elems = s->stack_lf.elems;
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unsigned int i;
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for (i = 0; i < count; i++)
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__rte_stack_lf_push_elems(&s->stack_lf.free,
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&elems[i], &elems[i], 1);
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}
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ssize_t
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rte_stack_lf_get_memsize(unsigned int count)
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{
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ssize_t sz = sizeof(struct rte_stack);
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sz += RTE_CACHE_LINE_ROUNDUP(count * sizeof(struct rte_stack_lf_elem));
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/* Add padding to avoid false sharing conflicts caused by
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* next-line hardware prefetchers.
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*/
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sz += 2 * RTE_CACHE_LINE_SIZE;
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return sz;
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}
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