There are timing issues in the use of threads in some unit test cases for futex. A potentially good solution is to check whether the thread is in the sleep state after creating it.
A file named futex_thread.h is added, in which several thread-related functions are implemented to facilitate the solution of this problem. Signed-off-by: Yuwen Chen <[email protected]> --- v6->v7: 1. Changed `static` to `static inline` for all functions to prevent compiler warnings about unused functions. 2. Added `sleep_time_us` variable with zero-guard in __wait_for_thread() to prevent tight loop when timeout_us < WAIT_THREAD_RETRIES. 3. Removed fallback usleep(100ms) from futex_wait_for_thread(); the caller is now responsible for handling errors. 4. Added return value check for pthread_barrier_init(). 5. Added pthread_barrier_destroy() cleanup on pthread_create() failure. .../selftests/futex/functional/Makefile | 3 +- .../selftests/futex/include/futex_thread.h | 114 ++++++++++++++++++ 2 files changed, 116 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/futex/include/futex_thread.h diff --git a/tools/testing/selftests/futex/functional/Makefile b/tools/testing/selftests/futex/functional/Makefile index 5c1c824f97400..724e8216e41b1 100644 --- a/tools/testing/selftests/futex/functional/Makefile +++ b/tools/testing/selftests/futex/functional/Makefile @@ -11,7 +11,8 @@ endif LOCAL_HDRS := \ ../include/futextest.h \ - ../include/atomic.h + ../include/atomic.h \ + ../include/futex_thread.h TEST_GEN_PROGS := \ futex_wait_timeout \ futex_wait_wouldblock \ diff --git a/tools/testing/selftests/futex/include/futex_thread.h b/tools/testing/selftests/futex/include/futex_thread.h new file mode 100644 index 0000000000000..49ae687012fe5 --- /dev/null +++ b/tools/testing/selftests/futex/include/futex_thread.h @@ -0,0 +1,114 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ + +#ifndef _FUTEX_THREAD_H +#define _FUTEX_THREAD_H +#include <stdio.h> +#include <string.h> +#include <errno.h> +#include <pthread.h> +#include <unistd.h> + +#define USEC_PER_SEC 1000000L +#define WAIT_THREAD_RETRIES 100 + +struct futex_thread { + pthread_t thread; + pthread_barrier_t barrier; + pid_t tid; + int (*threadfn)(void *arg); + void *arg; + int retval; +}; + +static inline int __wait_for_thread(FILE *fp, int timeout_us) +{ + char buf[80] = ""; + int i; + int sleep_time_us = timeout_us / WAIT_THREAD_RETRIES; + + if (sleep_time_us <= 0) + sleep_time_us = 1; + + for (i = 0; i < WAIT_THREAD_RETRIES; i++) { + if (!fgets(buf, sizeof(buf), fp)) + return -EIO; + if (!strncmp(buf, "futex", 5)) + return 0; + usleep(sleep_time_us); + rewind(fp); + } + return -ETIMEDOUT; +} + +static void *__futex_thread_fn(void *arg) +{ + struct futex_thread *t = arg; + + t->tid = gettid(); + pthread_barrier_wait(&t->barrier); + t->retval = t->threadfn(t->arg); + return NULL; +} + +/** + * futex_wait_for_thread - Wait for the child thread to sleep in the futex context + * @t: Thread handle. + * @timeout_us: The timeout for waiting for the thread to enter the sleep state. + */ +static inline int futex_wait_for_thread(struct futex_thread *t, int timeout_us) +{ + char fname[80]; + FILE *fp; + int res; + + snprintf(fname, sizeof(fname), "/proc/%d/wchan", t->tid); + fp = fopen(fname, "r"); + if (!fp) { + return -EIO; + } + + res = __wait_for_thread(fp, timeout_us); + fclose(fp); + return res; +} + +/** + * futex_thread_create - Create a new thread for testing. + * @t: The handle of the newly created thread. + * @threadfn: The new thread starts execution by invoking threadfn + * @arg: The parameters passed to threadfn. + */ +static inline int futex_thread_create(struct futex_thread *t, int (*threadfn)(void *), void *arg) +{ + int ret; + + ret = pthread_barrier_init(&t->barrier, NULL, 2); + if (ret) + return ret; + + t->tid = 0; + t->threadfn = threadfn; + t->arg = arg; + + ret = pthread_create(&t->thread, NULL, __futex_thread_fn, t); + if (ret) { + pthread_barrier_destroy(&t->barrier); + return ret; + } + + pthread_barrier_wait(&t->barrier); + return 0; +} + +/** + * futex_thread_destroy - Wait for and reclaim the resources of the thread. + * @t: Thread handle. + */ +static inline int futex_thread_destroy(struct futex_thread *t) +{ + pthread_join(t->thread, NULL); + pthread_barrier_destroy(&t->barrier); + return t->retval; +} + +#endif -- 2.34.1
