mirror of https://gitee.com/openkylin/linux.git
313 lines
7.0 KiB
C
313 lines
7.0 KiB
C
// SPDX-License-Identifier: LGPL-2.1
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#define _GNU_SOURCE
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#include <assert.h>
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#include <pthread.h>
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#include <sched.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stddef.h>
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#include "rseq.h"
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#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
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struct percpu_lock_entry {
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intptr_t v;
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} __attribute__((aligned(128)));
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struct percpu_lock {
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struct percpu_lock_entry c[CPU_SETSIZE];
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};
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struct test_data_entry {
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intptr_t count;
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} __attribute__((aligned(128)));
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struct spinlock_test_data {
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struct percpu_lock lock;
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struct test_data_entry c[CPU_SETSIZE];
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int reps;
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};
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struct percpu_list_node {
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intptr_t data;
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struct percpu_list_node *next;
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};
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struct percpu_list_entry {
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struct percpu_list_node *head;
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} __attribute__((aligned(128)));
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struct percpu_list {
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struct percpu_list_entry c[CPU_SETSIZE];
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};
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/* A simple percpu spinlock. Returns the cpu lock was acquired on. */
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int rseq_this_cpu_lock(struct percpu_lock *lock)
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{
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int cpu;
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for (;;) {
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int ret;
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cpu = rseq_cpu_start();
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ret = rseq_cmpeqv_storev(&lock->c[cpu].v,
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0, 1, cpu);
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if (rseq_likely(!ret))
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break;
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/* Retry if comparison fails or rseq aborts. */
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}
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/*
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* Acquire semantic when taking lock after control dependency.
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* Matches rseq_smp_store_release().
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*/
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rseq_smp_acquire__after_ctrl_dep();
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return cpu;
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}
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void rseq_percpu_unlock(struct percpu_lock *lock, int cpu)
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{
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assert(lock->c[cpu].v == 1);
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/*
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* Release lock, with release semantic. Matches
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* rseq_smp_acquire__after_ctrl_dep().
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*/
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rseq_smp_store_release(&lock->c[cpu].v, 0);
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}
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void *test_percpu_spinlock_thread(void *arg)
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{
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struct spinlock_test_data *data = arg;
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int i, cpu;
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if (rseq_register_current_thread()) {
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fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n",
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errno, strerror(errno));
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abort();
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}
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for (i = 0; i < data->reps; i++) {
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cpu = rseq_this_cpu_lock(&data->lock);
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data->c[cpu].count++;
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rseq_percpu_unlock(&data->lock, cpu);
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}
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if (rseq_unregister_current_thread()) {
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fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n",
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errno, strerror(errno));
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abort();
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}
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return NULL;
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}
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/*
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* A simple test which implements a sharded counter using a per-cpu
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* lock. Obviously real applications might prefer to simply use a
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* per-cpu increment; however, this is reasonable for a test and the
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* lock can be extended to synchronize more complicated operations.
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*/
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void test_percpu_spinlock(void)
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{
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const int num_threads = 200;
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int i;
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uint64_t sum;
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pthread_t test_threads[num_threads];
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struct spinlock_test_data data;
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memset(&data, 0, sizeof(data));
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data.reps = 5000;
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for (i = 0; i < num_threads; i++)
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pthread_create(&test_threads[i], NULL,
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test_percpu_spinlock_thread, &data);
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for (i = 0; i < num_threads; i++)
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pthread_join(test_threads[i], NULL);
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sum = 0;
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for (i = 0; i < CPU_SETSIZE; i++)
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sum += data.c[i].count;
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assert(sum == (uint64_t)data.reps * num_threads);
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}
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void this_cpu_list_push(struct percpu_list *list,
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struct percpu_list_node *node,
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int *_cpu)
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{
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int cpu;
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for (;;) {
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intptr_t *targetptr, newval, expect;
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int ret;
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cpu = rseq_cpu_start();
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/* Load list->c[cpu].head with single-copy atomicity. */
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expect = (intptr_t)RSEQ_READ_ONCE(list->c[cpu].head);
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newval = (intptr_t)node;
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targetptr = (intptr_t *)&list->c[cpu].head;
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node->next = (struct percpu_list_node *)expect;
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ret = rseq_cmpeqv_storev(targetptr, expect, newval, cpu);
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if (rseq_likely(!ret))
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break;
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/* Retry if comparison fails or rseq aborts. */
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}
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if (_cpu)
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*_cpu = cpu;
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}
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/*
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* Unlike a traditional lock-less linked list; the availability of a
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* rseq primitive allows us to implement pop without concerns over
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* ABA-type races.
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*/
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struct percpu_list_node *this_cpu_list_pop(struct percpu_list *list,
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int *_cpu)
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{
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for (;;) {
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struct percpu_list_node *head;
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intptr_t *targetptr, expectnot, *load;
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off_t offset;
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int ret, cpu;
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cpu = rseq_cpu_start();
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targetptr = (intptr_t *)&list->c[cpu].head;
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expectnot = (intptr_t)NULL;
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offset = offsetof(struct percpu_list_node, next);
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load = (intptr_t *)&head;
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ret = rseq_cmpnev_storeoffp_load(targetptr, expectnot,
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offset, load, cpu);
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if (rseq_likely(!ret)) {
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if (_cpu)
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*_cpu = cpu;
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return head;
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}
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if (ret > 0)
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return NULL;
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/* Retry if rseq aborts. */
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}
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}
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/*
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* __percpu_list_pop is not safe against concurrent accesses. Should
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* only be used on lists that are not concurrently modified.
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*/
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struct percpu_list_node *__percpu_list_pop(struct percpu_list *list, int cpu)
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{
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struct percpu_list_node *node;
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node = list->c[cpu].head;
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if (!node)
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return NULL;
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list->c[cpu].head = node->next;
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return node;
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}
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void *test_percpu_list_thread(void *arg)
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{
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int i;
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struct percpu_list *list = (struct percpu_list *)arg;
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if (rseq_register_current_thread()) {
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fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n",
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errno, strerror(errno));
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abort();
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}
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for (i = 0; i < 100000; i++) {
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struct percpu_list_node *node;
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node = this_cpu_list_pop(list, NULL);
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sched_yield(); /* encourage shuffling */
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if (node)
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this_cpu_list_push(list, node, NULL);
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}
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if (rseq_unregister_current_thread()) {
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fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n",
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errno, strerror(errno));
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abort();
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}
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return NULL;
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}
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/* Simultaneous modification to a per-cpu linked list from many threads. */
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void test_percpu_list(void)
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{
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int i, j;
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uint64_t sum = 0, expected_sum = 0;
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struct percpu_list list;
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pthread_t test_threads[200];
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cpu_set_t allowed_cpus;
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memset(&list, 0, sizeof(list));
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/* Generate list entries for every usable cpu. */
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sched_getaffinity(0, sizeof(allowed_cpus), &allowed_cpus);
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for (i = 0; i < CPU_SETSIZE; i++) {
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if (!CPU_ISSET(i, &allowed_cpus))
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continue;
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for (j = 1; j <= 100; j++) {
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struct percpu_list_node *node;
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expected_sum += j;
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node = malloc(sizeof(*node));
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assert(node);
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node->data = j;
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node->next = list.c[i].head;
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list.c[i].head = node;
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}
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}
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for (i = 0; i < 200; i++)
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pthread_create(&test_threads[i], NULL,
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test_percpu_list_thread, &list);
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for (i = 0; i < 200; i++)
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pthread_join(test_threads[i], NULL);
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for (i = 0; i < CPU_SETSIZE; i++) {
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struct percpu_list_node *node;
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if (!CPU_ISSET(i, &allowed_cpus))
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continue;
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while ((node = __percpu_list_pop(&list, i))) {
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sum += node->data;
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free(node);
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}
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}
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/*
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* All entries should now be accounted for (unless some external
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* actor is interfering with our allowed affinity while this
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* test is running).
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*/
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assert(sum == expected_sum);
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}
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int main(int argc, char **argv)
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{
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if (rseq_register_current_thread()) {
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fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n",
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errno, strerror(errno));
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goto error;
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}
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printf("spinlock\n");
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test_percpu_spinlock();
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printf("percpu_list\n");
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test_percpu_list();
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if (rseq_unregister_current_thread()) {
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fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n",
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errno, strerror(errno));
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goto error;
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}
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return 0;
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error:
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return -1;
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}
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