[librseq.git] / tests / basic_percpu_ops_test.c

// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: 2018-2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <assert.h>
#include <pthread.h>
#include <sched.h>
#include <stdint.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stddef.h>

#include <rseq/rseq.h>

#include "tap.h"

#define NR_TESTS 4

#define ARRAY_SIZE(arr)	(sizeof(arr) / sizeof((arr)[0]))

#ifdef BUILDOPT_RSEQ_PERCPU_MM_CID
# define RSEQ_PERCPU	RSEQ_PERCPU_MM_CID
static
int get_current_cpu_id(void)
{
	return rseq_current_mm_cid();
}
static
bool rseq_validate_cpu_id(void)
{
	return rseq_mm_cid_available();
}
#else
# define RSEQ_PERCPU	RSEQ_PERCPU_CPU_ID
static
int get_current_cpu_id(void)
{
	return rseq_cpu_start();
}
static
bool rseq_validate_cpu_id(void)
{
	return rseq_current_cpu_raw() >= 0;
}
#endif

struct percpu_lock_entry {
	intptr_t v;
} __attribute__((aligned(128)));

struct percpu_lock {
	struct percpu_lock_entry c[CPU_SETSIZE];
};

struct test_data_entry {
	intptr_t count;
} __attribute__((aligned(128)));

struct spinlock_test_data {
	struct percpu_lock lock;
	struct test_data_entry c[CPU_SETSIZE];
	int reps;
};

struct percpu_list_node {
	intptr_t data;
	struct percpu_list_node *next;
};

struct percpu_list_entry {
	struct percpu_list_node *head;
} __attribute__((aligned(128)));

struct percpu_list {
	struct percpu_list_entry c[CPU_SETSIZE];
};

/* A simple percpu spinlock.  Returns the cpu lock was acquired on. */
static int rseq_this_cpu_lock(struct percpu_lock *lock)
{
	int cpu;

	for (;;) {
		int ret;

		cpu = get_current_cpu_id();
		ret = rseq_cmpeqv_storev(RSEQ_MO_RELAXED, RSEQ_PERCPU,
					 &lock->c[cpu].v, 0, 1, cpu);
		if (rseq_likely(!ret))
			break;
		/* Retry if comparison fails or rseq aborts. */
	}
	/*
	 * Acquire semantic when taking lock after control dependency.
	 * Matches rseq_smp_store_release().
	 */
	rseq_smp_acquire__after_ctrl_dep();
	return cpu;
}

static void rseq_percpu_unlock(struct percpu_lock *lock, int cpu)
{
	assert(lock->c[cpu].v == 1);
	/*
	 * Release lock, with release semantic. Matches
	 * rseq_smp_acquire__after_ctrl_dep().
	 */
	rseq_smp_store_release(&lock->c[cpu].v, 0);
}

static void *test_percpu_spinlock_thread(void *arg)
{
	struct spinlock_test_data *data = (struct spinlock_test_data *) arg;
	int i, cpu;

	if (rseq_register_current_thread()) {
		fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n",
			errno, strerror(errno));
		abort();
	}
	for (i = 0; i < data->reps; i++) {
		cpu = rseq_this_cpu_lock(&data->lock);
		data->c[cpu].count++;
		rseq_percpu_unlock(&data->lock, cpu);
	}
	if (rseq_unregister_current_thread()) {
		fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n",
			errno, strerror(errno));
		abort();
	}

	return NULL;
}

/*
 * A simple test which implements a sharded counter using a per-cpu
 * lock.  Obviously real applications might prefer to simply use a
 * per-cpu increment; however, this is reasonable for a test and the
 * lock can be extended to synchronize more complicated operations.
 */
static void test_percpu_spinlock(void)
{
	const int num_threads = 200;
	int i;
	uint64_t sum, expected_sum;
	pthread_t test_threads[num_threads];
	struct spinlock_test_data data;

	diag("spinlock");

	memset(&data, 0, sizeof(data));
	data.reps = 5000;

	for (i = 0; i < num_threads; i++)
		pthread_create(&test_threads[i], NULL,
			       test_percpu_spinlock_thread, &data);

	for (i = 0; i < num_threads; i++)
		pthread_join(test_threads[i], NULL);

	sum = 0;
	for (i = 0; i < CPU_SETSIZE; i++)
		sum += data.c[i].count;

	expected_sum = (uint64_t)data.reps * num_threads;

	ok(sum == expected_sum, "spinlock - sum (%" PRIu64 " == %" PRIu64 ")", sum, expected_sum);
}

static void this_cpu_list_push(struct percpu_list *list,
			struct percpu_list_node *node,
			int *_cpu)
{
	int cpu;

	for (;;) {
		intptr_t *targetptr, newval, expect;
		int ret;

		cpu = get_current_cpu_id();
		/* Load list->c[cpu].head with single-copy atomicity. */
		expect = (intptr_t)RSEQ_READ_ONCE(list->c[cpu].head);
		newval = (intptr_t)node;
		targetptr = (intptr_t *)&list->c[cpu].head;
		node->next = (struct percpu_list_node *)expect;
		ret = rseq_cmpeqv_storev(RSEQ_MO_RELAXED, RSEQ_PERCPU,
					 targetptr, expect, newval, cpu);
		if (rseq_likely(!ret))
			break;
		/* Retry if comparison fails or rseq aborts. */
	}
	if (_cpu)
		*_cpu = cpu;
}

/*
 * Unlike a traditional lock-less linked list; the availability of a
 * rseq primitive allows us to implement pop without concerns over
 * ABA-type races.
 */
static struct percpu_list_node *this_cpu_list_pop(struct percpu_list *list,
					   int *_cpu)
{
	for (;;) {
		struct percpu_list_node *head;
		intptr_t *targetptr, expectnot, *load;
		long offset;
		int ret, cpu;

		cpu = get_current_cpu_id();
		targetptr = (intptr_t *)&list->c[cpu].head;
		expectnot = (intptr_t)NULL;
		offset = offsetof(struct percpu_list_node, next);
		load = (intptr_t *)&head;
		ret = rseq_cmpnev_storeoffp_load(RSEQ_MO_RELAXED, RSEQ_PERCPU,
						 targetptr, expectnot,
						 offset, load, cpu);
		if (rseq_likely(!ret)) {
			if (_cpu)
				*_cpu = cpu;
			return head;
		}
		if (ret > 0)
			return NULL;
		/* Retry if rseq aborts. */
	}
}

/*
 * __percpu_list_pop is not safe against concurrent accesses. Should
 * only be used on lists that are not concurrently modified.
 */
static struct percpu_list_node *__percpu_list_pop(struct percpu_list *list, int cpu)
{
	struct percpu_list_node *node;

	node = list->c[cpu].head;
	if (!node)
		return NULL;
	list->c[cpu].head = node->next;
	return node;
}

static void *test_percpu_list_thread(void *arg)
{
	int i;
	struct percpu_list *list = (struct percpu_list *)arg;

	if (rseq_register_current_thread()) {
		fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n",
			errno, strerror(errno));
		abort();
	}

	for (i = 0; i < 100000; i++) {
		struct percpu_list_node *node;

		node = this_cpu_list_pop(list, NULL);
		sched_yield();  /* encourage shuffling */
		if (node)
			this_cpu_list_push(list, node, NULL);
	}

	if (rseq_unregister_current_thread()) {
		fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n",
			errno, strerror(errno));
		abort();
	}

	return NULL;
}

/* Simultaneous modification to a per-cpu linked list from many threads.  */
static void test_percpu_list(void)
{
	int i, j;
	uint64_t sum = 0, expected_sum = 0;
	struct percpu_list list;
	pthread_t test_threads[200];
	cpu_set_t allowed_cpus;

	diag("percpu_list");

	memset(&list, 0, sizeof(list));

	/* Generate list entries for every usable cpu. */
	sched_getaffinity(0, sizeof(allowed_cpus), &allowed_cpus);
	for (i = 0; i < CPU_SETSIZE; i++) {
		if (!CPU_ISSET(i, &allowed_cpus))
			continue;
		for (j = 1; j <= 100; j++) {
			struct percpu_list_node *node;

			expected_sum += j;

			node = (struct percpu_list_node *) malloc(sizeof(*node));
			assert(node);
			node->data = j;
			node->next = list.c[i].head;
			list.c[i].head = node;
		}
	}

	for (i = 0; i < 200; i++)
		pthread_create(&test_threads[i], NULL,
		       test_percpu_list_thread, &list);

	for (i = 0; i < 200; i++)
		pthread_join(test_threads[i], NULL);

	for (i = 0; i < CPU_SETSIZE; i++) {
		struct percpu_list_node *node;

		if (!CPU_ISSET(i, &allowed_cpus))
			continue;

		while ((node = __percpu_list_pop(&list, i))) {
			sum += node->data;
			free(node);
		}
	}

	/*
	 * All entries should now be accounted for (unless some external
	 * actor is interfering with our allowed affinity while this
	 * test is running).
	 */
	ok(sum == expected_sum, "percpu_list - sum (%" PRIu64 " == %" PRIu64 ")", sum, expected_sum);
}

int main(void)
{
	plan_tests(NR_TESTS);

	if (!rseq_available(RSEQ_AVAILABLE_QUERY_KERNEL)) {
		skip(NR_TESTS, "The rseq syscall is unavailable");
		goto end;
	}

	if (rseq_register_current_thread()) {
		fail("rseq_register_current_thread(...) failed(%d): %s\n",
			errno, strerror(errno));
		goto end;
	} else {
		pass("Registered current thread with rseq");
	}
	if (!rseq_validate_cpu_id()) {
		skip(NR_TESTS, "Error: cpu id getter unavailable");
		goto end;
	}
	test_percpu_spinlock();
	test_percpu_list();

	if (rseq_unregister_current_thread()) {
		fail("rseq_unregister_current_thread(...) failed(%d): %s\n",
			errno, strerror(errno));
		goto end;
	} else {
		pass("Unregistered current thread with rseq");
	}
end:
	exit(exit_status());
}
Commit	Line	Data
90702366	1	// SPDX-License-Identifier: MIT
f2d7b530	2	// SPDX-FileCopyrightText: 2018-2022 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
b848736e MD	3	#ifndef _GNU_SOURCE
	4	#define _GNU_SOURCE
	5	#endif
	6	#include <assert.h>
	7	#include <pthread.h>
	8	#include <sched.h>
	9	#include <stdint.h>
a91728e0	10	#include <inttypes.h>
b848736e MD	11	#include <stdio.h>
	12	#include <stdlib.h>
	13	#include <string.h>
	14	#include <stddef.h>
	15
	16	#include <rseq/rseq.h>
	17
544cdc88 MJ	18	#include "tap.h"
544cdc88 MJ	19
d1cdec98	20	#define NR_TESTS 4
544cdc88	21
b848736e MD	22	#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
b848736e MD	23
40293a78 MD	24	#ifdef BUILDOPT_RSEQ_PERCPU_MM_CID
	25	# define RSEQ_PERCPU RSEQ_PERCPU_MM_CID
	26	static
	27	int get_current_cpu_id(void)
	28	{
	29	return rseq_current_mm_cid();
	30	}
	31	static
	32	bool rseq_validate_cpu_id(void)
	33	{
	34	return rseq_mm_cid_available();
	35	}
	36	#else
	37	# define RSEQ_PERCPU RSEQ_PERCPU_CPU_ID
	38	static
	39	int get_current_cpu_id(void)
	40	{
	41	return rseq_cpu_start();
	42	}
	43	static
	44	bool rseq_validate_cpu_id(void)
	45	{
	46	return rseq_current_cpu_raw() >= 0;
	47	}
	48	#endif
	49
b848736e MD	50	struct percpu_lock_entry {
	51	intptr_t v;
	52	} __attribute__((aligned(128)));
	53
	54	struct percpu_lock {
	55	struct percpu_lock_entry c[CPU_SETSIZE];
	56	};
	57
	58	struct test_data_entry {
	59	intptr_t count;
	60	} __attribute__((aligned(128)));
	61
	62	struct spinlock_test_data {
	63	struct percpu_lock lock;
	64	struct test_data_entry c[CPU_SETSIZE];
	65	int reps;
	66	};
	67
	68	struct percpu_list_node {
	69	intptr_t data;
	70	struct percpu_list_node *next;
	71	};
	72
	73	struct percpu_list_entry {
	74	struct percpu_list_node *head;
	75	} __attribute__((aligned(128)));
	76
	77	struct percpu_list {
	78	struct percpu_list_entry c[CPU_SETSIZE];
	79	};
	80
	81	/* A simple percpu spinlock. Returns the cpu lock was acquired on. */
6e284b80	82	static int rseq_this_cpu_lock(struct percpu_lock *lock)
b848736e MD	83	{
	84	int cpu;
	85
	86	for (;;) {
	87	int ret;
	88
40293a78 MD	89	cpu = get_current_cpu_id();
	90	ret = rseq_cmpeqv_storev(RSEQ_MO_RELAXED, RSEQ_PERCPU,
	91	&lock->c[cpu].v, 0, 1, cpu);
b848736e MD	92	if (rseq_likely(!ret))
	93	break;
	94	/* Retry if comparison fails or rseq aborts. */
	95	}
	96	/*
	97	* Acquire semantic when taking lock after control dependency.
	98	* Matches rseq_smp_store_release().
	99	*/
	100	rseq_smp_acquire__after_ctrl_dep();
	101	return cpu;
	102	}
	103
6e284b80	104	static void rseq_percpu_unlock(struct percpu_lock *lock, int cpu)
b848736e MD	105	{
	106	assert(lock->c[cpu].v == 1);
	107	/*
	108	* Release lock, with release semantic. Matches
	109	* rseq_smp_acquire__after_ctrl_dep().
	110	*/
	111	rseq_smp_store_release(&lock->c[cpu].v, 0);
	112	}
	113
6e284b80	114	static void test_percpu_spinlock_thread(void arg)
b848736e	115	{
d268885a	116	struct spinlock_test_data data = (struct spinlock_test_data ) arg;
b848736e MD	117	int i, cpu;
	118
	119	if (rseq_register_current_thread()) {
	120	fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n",
	121	errno, strerror(errno));
	122	abort();
	123	}
	124	for (i = 0; i < data->reps; i++) {
	125	cpu = rseq_this_cpu_lock(&data->lock);
	126	data->c[cpu].count++;
	127	rseq_percpu_unlock(&data->lock, cpu);
	128	}
	129	if (rseq_unregister_current_thread()) {
	130	fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n",
	131	errno, strerror(errno));
	132	abort();
	133	}
	134
	135	return NULL;
	136	}
	137
	138	/*
	139	* A simple test which implements a sharded counter using a per-cpu
	140	* lock. Obviously real applications might prefer to simply use a
	141	* per-cpu increment; however, this is reasonable for a test and the
	142	* lock can be extended to synchronize more complicated operations.
	143	*/
6e284b80	144	static void test_percpu_spinlock(void)
b848736e MD	145	{
	146	const int num_threads = 200;
	147	int i;
a91728e0	148	uint64_t sum, expected_sum;
b848736e MD	149	pthread_t test_threads[num_threads];
	150	struct spinlock_test_data data;
	151
544cdc88 MJ	152	diag("spinlock");
544cdc88 MJ	153
b848736e MD	154	memset(&data, 0, sizeof(data));
	155	data.reps = 5000;
	156
	157	for (i = 0; i < num_threads; i++)
	158	pthread_create(&test_threads[i], NULL,
	159	test_percpu_spinlock_thread, &data);
	160
	161	for (i = 0; i < num_threads; i++)
	162	pthread_join(test_threads[i], NULL);
	163
	164	sum = 0;
	165	for (i = 0; i < CPU_SETSIZE; i++)
	166	sum += data.c[i].count;
	167
a91728e0 MJ	168	expected_sum = (uint64_t)data.reps * num_threads;
	169
	170	ok(sum == expected_sum, "spinlock - sum (%" PRIu64 " == %" PRIu64 ")", sum, expected_sum);
b848736e MD	171	}
b848736e MD	172
6e284b80	173	static void this_cpu_list_push(struct percpu_list *list,
b848736e MD	174	struct percpu_list_node *node,
	175	int *_cpu)
	176	{
	177	int cpu;
	178
	179	for (;;) {
	180	intptr_t *targetptr, newval, expect;
	181	int ret;
	182
40293a78	183	cpu = get_current_cpu_id();
b848736e MD	184	/* Load list->c[cpu].head with single-copy atomicity. */
	185	expect = (intptr_t)RSEQ_READ_ONCE(list->c[cpu].head);
	186	newval = (intptr_t)node;
	187	targetptr = (intptr_t *)&list->c[cpu].head;
	188	node->next = (struct percpu_list_node *)expect;
40293a78 MD	189	ret = rseq_cmpeqv_storev(RSEQ_MO_RELAXED, RSEQ_PERCPU,
40293a78 MD	190	targetptr, expect, newval, cpu);
b848736e MD	191	if (rseq_likely(!ret))
	192	break;
	193	/* Retry if comparison fails or rseq aborts. */
	194	}
	195	if (_cpu)
	196	*_cpu = cpu;
	197	}
	198
	199	/*
	200	* Unlike a traditional lock-less linked list; the availability of a
	201	* rseq primitive allows us to implement pop without concerns over
	202	* ABA-type races.
	203	*/
6e284b80	204	static struct percpu_list_node this_cpu_list_pop(struct percpu_list list,
b848736e MD	205	int *_cpu)
	206	{
	207	for (;;) {
	208	struct percpu_list_node *head;
	209	intptr_t targetptr, expectnot, load;
d35eae6b MD	210	long offset;
d35eae6b MD	211	int ret, cpu;
b848736e	212
40293a78	213	cpu = get_current_cpu_id();
b848736e MD	214	targetptr = (intptr_t *)&list->c[cpu].head;
	215	expectnot = (intptr_t)NULL;
	216	offset = offsetof(struct percpu_list_node, next);
	217	load = (intptr_t *)&head;
40293a78 MD	218	ret = rseq_cmpnev_storeoffp_load(RSEQ_MO_RELAXED, RSEQ_PERCPU,
40293a78 MD	219	targetptr, expectnot,
b848736e MD	220	offset, load, cpu);
	221	if (rseq_likely(!ret)) {
	222	if (_cpu)
	223	*_cpu = cpu;
	224	return head;
	225	}
	226	if (ret > 0)
	227	return NULL;
	228	/* Retry if rseq aborts. */
	229	}
	230	}
	231
	232	/*
	233	* __percpu_list_pop is not safe against concurrent accesses. Should
	234	* only be used on lists that are not concurrently modified.
	235	*/
6e284b80	236	static struct percpu_list_node __percpu_list_pop(struct percpu_list list, int cpu)
b848736e MD	237	{
	238	struct percpu_list_node *node;
	239
	240	node = list->c[cpu].head;
	241	if (!node)
	242	return NULL;
	243	list->c[cpu].head = node->next;
	244	return node;
	245	}
	246
6e284b80	247	static void test_percpu_list_thread(void arg)
b848736e MD	248	{
	249	int i;
	250	struct percpu_list list = (struct percpu_list )arg;
	251
	252	if (rseq_register_current_thread()) {
	253	fprintf(stderr, "Error: rseq_register_current_thread(...) failed(%d): %s\n",
	254	errno, strerror(errno));
	255	abort();
	256	}
	257
	258	for (i = 0; i < 100000; i++) {
	259	struct percpu_list_node *node;
	260
	261	node = this_cpu_list_pop(list, NULL);
	262	sched_yield(); /* encourage shuffling */
	263	if (node)
	264	this_cpu_list_push(list, node, NULL);
	265	}
	266
	267	if (rseq_unregister_current_thread()) {
	268	fprintf(stderr, "Error: rseq_unregister_current_thread(...) failed(%d): %s\n",
	269	errno, strerror(errno));
	270	abort();
	271	}
	272
	273	return NULL;
	274	}
	275
	276	/* Simultaneous modification to a per-cpu linked list from many threads. */
6e284b80	277	static void test_percpu_list(void)
b848736e MD	278	{
	279	int i, j;
	280	uint64_t sum = 0, expected_sum = 0;
	281	struct percpu_list list;
	282	pthread_t test_threads[200];
	283	cpu_set_t allowed_cpus;
	284
544cdc88 MJ	285	diag("percpu_list");
544cdc88 MJ	286
b848736e MD	287	memset(&list, 0, sizeof(list));
	288
	289	/* Generate list entries for every usable cpu. */
	290	sched_getaffinity(0, sizeof(allowed_cpus), &allowed_cpus);
	291	for (i = 0; i < CPU_SETSIZE; i++) {
	292	if (!CPU_ISSET(i, &allowed_cpus))
	293	continue;
	294	for (j = 1; j <= 100; j++) {
	295	struct percpu_list_node *node;
	296
	297	expected_sum += j;
	298
d268885a	299	node = (struct percpu_list_node ) malloc(sizeof(node));
b848736e MD	300	assert(node);
	301	node->data = j;
	302	node->next = list.c[i].head;
	303	list.c[i].head = node;
	304	}
	305	}
	306
	307	for (i = 0; i < 200; i++)
	308	pthread_create(&test_threads[i], NULL,
	309	test_percpu_list_thread, &list);
	310
	311	for (i = 0; i < 200; i++)
	312	pthread_join(test_threads[i], NULL);
	313
	314	for (i = 0; i < CPU_SETSIZE; i++) {
	315	struct percpu_list_node *node;
	316
	317	if (!CPU_ISSET(i, &allowed_cpus))
	318	continue;
	319
	320	while ((node = __percpu_list_pop(&list, i))) {
	321	sum += node->data;
	322	free(node);
	323	}
	324	}
	325
	326	/*
	327	* All entries should now be accounted for (unless some external
	328	* actor is interfering with our allowed affinity while this
	329	* test is running).
	330	*/
a91728e0	331	ok(sum == expected_sum, "percpu_list - sum (%" PRIu64 " == %" PRIu64 ")", sum, expected_sum);
b848736e MD	332	}
	333
	334	int main(void)
	335	{
544cdc88 MJ	336	plan_tests(NR_TESTS);
544cdc88 MJ	337
8b34114a	338	if (!rseq_available(RSEQ_AVAILABLE_QUERY_KERNEL)) {
d1cdec98 MJ	339	skip(NR_TESTS, "The rseq syscall is unavailable");
	340	goto end;
	341	}
	342
b848736e	343	if (rseq_register_current_thread()) {
d1cdec98	344	fail("rseq_register_current_thread(...) failed(%d): %s\n",
b848736e	345	errno, strerror(errno));
d1cdec98 MJ	346	goto end;
	347	} else {
	348	pass("Registered current thread with rseq");
b848736e	349	}
40293a78 MD	350	if (!rseq_validate_cpu_id()) {
	351	skip(NR_TESTS, "Error: cpu id getter unavailable");
	352	goto end;
	353	}
b848736e	354	test_percpu_spinlock();
b848736e	355	test_percpu_list();
544cdc88	356
b848736e	357	if (rseq_unregister_current_thread()) {
d1cdec98	358	fail("rseq_unregister_current_thread(...) failed(%d): %s\n",
b848736e	359	errno, strerror(errno));
d1cdec98 MJ	360	goto end;
	361	} else {
	362	pass("Unregistered current thread with rseq");
b848736e	363	}
d1cdec98 MJ	364	end:
d1cdec98 MJ	365	exit(exit_status());
b848736e	366	}