blob: e7fc77f64b41218237a4b35cd7586938f0447a7e [file] [log] [blame]
// Copyright 2019 The ChromiumOS Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <errno.h>
#include <sched.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
// Amount of time to spin before returning.
const int kSpinNs = 1e9; // 1 second
// Number of recursive calls to make.
const int kRecursionDepth = 8;
// Returns the monotonically-increasing time as nanoseconds since the epoch.
int64_t GetTimeNs() {
struct timespec ts = {0};
if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0) {
fprintf(stderr, "clock_gettime: %s", strerror(errno));
exit(1);
}
return 1e9 * ts.tv_sec + ts.tv_nsec;
}
// Calls itself n times. The innermost call spins for a short period of time
// before returning.
__attribute__((noinline)) void Recurse(int n) {
if (n > 0) {
Recurse(n-1);
return;
}
const int64_t start = GetTimeNs();
while (1) {
if (GetTimeNs() - start >= kSpinNs) {
break;
}
sched_yield();
}
}
int main() {
Recurse(kRecursionDepth);
return 0;
}