Messages in this thread Patch in this message | | | From | Peter Oskolkov <> | Subject | [PATCH for 5.9 v2 4/4] selftests/futex: add futex_swap selftest | Date | Mon, 3 Aug 2020 15:15:10 -0700 |
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From: Peter Oskolkov <posk@google.com>
This is the final patch in FUTEX_SWAP patchset. It adds a test/benchmark to validate the behavior and compare the performance of a new FUTEX_SWAP futex operation to a pair of FUTEX_WAKE/FUTEX_WAIT calls.
Detailed API design and behavior considerations are provided in the commit messages of the previous patches.
Signed-off-by: Peter Oskolkov <posk@google.com> --- .../selftests/futex/functional/.gitignore | 1 + .../selftests/futex/functional/Makefile | 1 + .../selftests/futex/functional/futex_swap.c | 209 ++++++++++++++++++ .../selftests/futex/include/futextest.h | 19 ++ 4 files changed, 230 insertions(+) create mode 100644 tools/testing/selftests/futex/functional/futex_swap.c
diff --git a/tools/testing/selftests/futex/functional/.gitignore b/tools/testing/selftests/futex/functional/.gitignore index 0efcd494daab..d661ef0946cc 100644 --- a/tools/testing/selftests/futex/functional/.gitignore +++ b/tools/testing/selftests/futex/functional/.gitignore @@ -2,6 +2,7 @@ futex_requeue_pi futex_requeue_pi_mismatched_ops futex_requeue_pi_signal_restart +futex_swap futex_wait_private_mapped_file futex_wait_timeout futex_wait_uninitialized_heap diff --git a/tools/testing/selftests/futex/functional/Makefile b/tools/testing/selftests/futex/functional/Makefile index 23207829ec75..6992fac38b15 100644 --- a/tools/testing/selftests/futex/functional/Makefile +++ b/tools/testing/selftests/futex/functional/Makefile @@ -13,6 +13,7 @@ TEST_GEN_FILES := \ futex_requeue_pi \ futex_requeue_pi_signal_restart \ futex_requeue_pi_mismatched_ops \ + futex_swap \ futex_wait_uninitialized_heap \ futex_wait_private_mapped_file diff --git a/tools/testing/selftests/futex/functional/futex_swap.c b/tools/testing/selftests/futex/functional/futex_swap.c new file mode 100644 index 000000000000..9034d04372d3 --- /dev/null +++ b/tools/testing/selftests/futex/functional/futex_swap.c @@ -0,0 +1,209 @@ +// SPDX-License-Identifier: GPL-2.0-or-later + +#include <errno.h> +#include <getopt.h> +#include <pthread.h> +#include <stdint.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <time.h> +#include "atomic.h" +#include "futextest.h" + +/* The futex the main thread waits on. */ +futex_t futex_main = FUTEX_INITIALIZER; +/* The futex the other thread wats on. */ +futex_t futex_other = FUTEX_INITIALIZER; + +/* The number of iterations to run (>1 => run benchmarks. */ +static int cfg_iterations = 1; + +/* If != 0, print diagnostic messages. */ +static int cfg_verbose; + +/* If == 0, do not use validation_counter. Useful for benchmarking. */ +static int cfg_validate = 1; + +/* How to swap threads. */ +#define SWAP_WAKE_WAIT 1 +#define SWAP_SWAP 2 + +/* Futex values. */ +#define FUTEX_WAITING 0 +#define FUTEX_WAKEUP 1 + +/* An atomic counter used to validate proper swapping. */ +static atomic_t validation_counter; + +void futex_swap_op(int mode, futex_t *futex_this, futex_t *futex_that) +{ + int ret; + + switch (mode) { + case SWAP_WAKE_WAIT: + futex_set(futex_this, FUTEX_WAITING); + futex_set(futex_that, FUTEX_WAKEUP); + futex_wake(futex_that, 1, FUTEX_PRIVATE_FLAG); + futex_wait(futex_this, FUTEX_WAITING, NULL, FUTEX_PRIVATE_FLAG); + if (*futex_this != FUTEX_WAKEUP) { + fprintf(stderr, "unexpected futex_this value on wakeup\n"); + exit(1); + } + break; + + case SWAP_SWAP: + futex_set(futex_this, FUTEX_WAITING); + futex_set(futex_that, FUTEX_WAKEUP); + ret = futex_swap(futex_this, FUTEX_WAITING, NULL, + futex_that, FUTEX_PRIVATE_FLAG); + if (ret < 0 && errno == ENOSYS) { + /* futex_swap not implemented */ + perror("futex_swap"); + exit(1); + } + if (*futex_this != FUTEX_WAKEUP) { + fprintf(stderr, "unexpected futex_this value on wakeup\n"); + exit(1); + } + break; + + default: + fprintf(stderr, "unknown mode in %s\n", __func__); + exit(1); + } +} + +void *other_thread(void *arg) +{ + int mode = *((int *)arg); + int counter; + + if (cfg_verbose) + printf("%s started\n", __func__); + + futex_wait(&futex_other, 0, NULL, FUTEX_PRIVATE_FLAG); + + for (counter = 0; counter < cfg_iterations; ++counter) { + if (cfg_validate) { + int prev = 2 * counter + 1; + + if (prev != atomic_cmpxchg(&validation_counter, prev, + prev + 1)) { + fprintf(stderr, "swap validation failed\n"); + exit(1); + } + } + futex_swap_op(mode, &futex_other, &futex_main); + } + + if (cfg_verbose) + printf("%s finished: %d iteration(s)\n", __func__, counter); + + return NULL; +} + +void run_test(int mode) +{ + struct timespec start, stop; + int ret, counter; + pthread_t thread; + uint64_t duration; + + futex_set(&futex_other, FUTEX_WAITING); + atomic_set(&validation_counter, 0); + ret = pthread_create(&thread, NULL, &other_thread, &mode); + if (ret) { + perror("pthread_create"); + exit(1); + } + + ret = clock_gettime(CLOCK_MONOTONIC, &start); + if (ret) { + perror("clock_gettime"); + exit(1); + } + + for (counter = 0; counter < cfg_iterations; ++counter) { + if (cfg_validate) { + int prev = 2 * counter; + + if (prev != atomic_cmpxchg(&validation_counter, prev, + prev + 1)) { + fprintf(stderr, "swap validation failed\n"); + exit(1); + } + } + futex_swap_op(mode, &futex_main, &futex_other); + } + if (cfg_validate && validation_counter.val != 2 * cfg_iterations) { + fprintf(stderr, "final swap validation failed\n"); + exit(1); + } + + ret = clock_gettime(CLOCK_MONOTONIC, &stop); + if (ret) { + perror("clock_gettime"); + exit(1); + } + + duration = (stop.tv_sec - start.tv_sec) * 1000000000LL + + stop.tv_nsec - start.tv_nsec; + if (cfg_verbose || cfg_iterations > 1) { + printf("completed %d swap and back iterations in %lu ns: %lu ns per swap\n", + cfg_iterations, duration, + duration / (cfg_iterations * 2)); + } + + /* The remote thread is blocked; send it the final wake. */ + futex_set(&futex_other, FUTEX_WAKEUP); + futex_wake(&futex_other, 1, FUTEX_PRIVATE_FLAG); + if (pthread_join(thread, NULL)) { + perror("pthread_join"); + exit(1); + } +} + +void usage(char *prog) +{ + printf("Usage: %s\n", prog); + printf(" -h Display this help message\n"); + printf(" -i N Use N iterations to benchmark\n"); + printf(" -n Do not validate swapping correctness\n"); + printf(" -v Print diagnostic messages\n"); +} + +int main(int argc, char *argv[]) +{ + int c; + + while ((c = getopt(argc, argv, "hi:nv")) != -1) { + switch (c) { + case 'h': + usage(basename(argv[0])); + exit(0); + case 'i': + cfg_iterations = atoi(optarg); + break; + case 'n': + cfg_validate = 0; + break; + case 'v': + cfg_verbose = 1; + break; + default: + usage(basename(argv[0])); + exit(1); + } + } + + printf("\n\n------- running SWAP_WAKE_WAIT -----------\n\n"); + run_test(SWAP_WAKE_WAIT); + printf("PASS\n"); + + printf("\n\n------- running SWAP_SWAP -----------\n\n"); + run_test(SWAP_SWAP); + printf("PASS\n"); + + return 0; +} diff --git a/tools/testing/selftests/futex/include/futextest.h b/tools/testing/selftests/futex/include/futextest.h index ddbcfc9b7bac..4d6a0a18445a 100644 --- a/tools/testing/selftests/futex/include/futextest.h +++ b/tools/testing/selftests/futex/include/futextest.h @@ -38,6 +38,9 @@ typedef volatile u_int32_t futex_t; #ifndef FUTEX_CMP_REQUEUE_PI #define FUTEX_CMP_REQUEUE_PI 12 #endif +#ifndef FUTEX_SWAP +#define FUTEX_SWAP 13 +#endif #ifndef FUTEX_WAIT_REQUEUE_PI_PRIVATE #define FUTEX_WAIT_REQUEUE_PI_PRIVATE (FUTEX_WAIT_REQUEUE_PI | \ FUTEX_PRIVATE_FLAG) @@ -46,6 +49,9 @@ typedef volatile u_int32_t futex_t; #define FUTEX_CMP_REQUEUE_PI_PRIVATE (FUTEX_CMP_REQUEUE_PI | \ FUTEX_PRIVATE_FLAG) #endif +#ifndef FUTEX_SWAP_PRIVATE +#define FUTEX_SWAP_PRIVATE (FUTEX_WAIT_WAKE | FUTEX_PRIVATE_FLAG) +#endif /** * futex() - SYS_futex syscall wrapper @@ -204,6 +210,19 @@ futex_cmp_requeue_pi(futex_t *uaddr, futex_t val, futex_t *uaddr2, int nr_wake, val, opflags); } +/** + * futex_swap() - block on uaddr and wake one task blocked on uaddr2. + * @uaddr: futex to block the current task on + * @timeout: relative timeout for the current task block + * @uaddr2: futex to wake tasks at (can be the same as uaddr) + */ +static inline int +futex_swap(futex_t *uaddr, futex_t val, struct timespec *timeout, + futex_t *uaddr2, int opflags) +{ + return futex(uaddr, FUTEX_SWAP, val, timeout, uaddr2, 0, opflags); +} + /** * futex_cmpxchg() - atomic compare and exchange * @uaddr: The address of the futex to be modified -- 2.25.1
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