#include #include #include #include #include #include #include #include #include #include #include /* * Usage: rw_seq_cst_vs_drop_caches /mnt/lustre/file0 /mnt/lustre2/file0 * Race reads of the same file on two client mounts vs writes and drop * caches to detect sequential consistency violations. Run * indefinately. all abort() if a consistency violation is found in * which case the wait status ($?) will be 134. */ #define handle_error(msg) \ do { perror(msg); exit(EXIT_FAILURE); } while (0) static int fd[2] = { -1, -1 }; /* u_max is total number of writes, which are time consumg because they are * contending with constant reads */ static uint64_t u, u_max = UINT64_MAX / 2; static uint64_t v[2]; static void *access_thread_start(void *unused) { ssize_t rc; int i; do { for (i = 0; i < 2; i++) { rc = pread(fd[i], &v[i], sizeof(v[i]), 0); if (rc < 0 || rc != sizeof(v[i])) handle_error("pread"); } } while (v[0] <= v[1]); fprintf(stderr, "error: u = %"PRIu64", v = %"PRIu64", %"PRIu64"\n", u, v[0], v[1]); abort(); } static char stderr_buf[4096]; int main(int argc, char *argv[]) { int drop_caches_fd = -1; pthread_t access_thread; struct stat st[2]; ssize_t rc; int i; setvbuf(stderr, stderr_buf, _IOLBF, sizeof(stderr_buf)); if (argc != 3) { fprintf(stderr, "Usage: %s /mnt/lustre/file0 /mnt/lustre2/file0\n", argv[0]); exit(EXIT_FAILURE); } drop_caches_fd = open("/proc/sys/vm/drop_caches", O_WRONLY); assert(!(drop_caches_fd < 0)); for (i = 0; i < 2; i++) { fd[i] = open(argv[i + 1], O_RDWR|O_CREAT|O_TRUNC, 0666); if (fd[i] < 0) handle_error("open"); rc = fstat(fd[i], &st[i]); if (rc < 0) handle_error("fstat"); } /* file0 and file1 should be the same file on two different * client mount points. */ if (st[0].st_dev != st[1].st_dev || st[0].st_ino != st[1].st_ino) { fprintf(stderr, "file mismatch\n"); exit(EXIT_FAILURE); } rc = pwrite(fd[0], &u, sizeof(u), 0); if (rc < 0 || rc != sizeof(u)) handle_error("pwrite"); rc = pthread_create(&access_thread, NULL, &access_thread_start, NULL); if (rc != 0) handle_error("pthread_create"); for (u = 1; u <= u_max; u++) { rc = pwrite(fd[0], &u, sizeof(u), 0); if (rc < 0 || rc != sizeof(u)) handle_error("pwrite"); rc = write(drop_caches_fd, "3\n", 2); if (rc < 0 || rc != 2) handle_error("drop caches"); } rc = pthread_cancel(access_thread); if (rc != 0) handle_error("pthread_cancel"); rc = pthread_join(access_thread, NULL); if (rc != 0) handle_error("pthread_join"); return 0; }