1*1253b9b8SPaul E. McKenney // SPDX-License-Identifier: GPL-2.0+ 2*1253b9b8SPaul E. McKenney /* 3*1253b9b8SPaul E. McKenney * Unit test for the clocksource watchdog. 4*1253b9b8SPaul E. McKenney * 5*1253b9b8SPaul E. McKenney * Copyright (C) 2021 Facebook, Inc. 6*1253b9b8SPaul E. McKenney * 7*1253b9b8SPaul E. McKenney * Author: Paul E. McKenney <paulmck@kernel.org> 8*1253b9b8SPaul E. McKenney */ 9*1253b9b8SPaul E. McKenney #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 10*1253b9b8SPaul E. McKenney 11*1253b9b8SPaul E. McKenney #include <linux/device.h> 12*1253b9b8SPaul E. McKenney #include <linux/clocksource.h> 13*1253b9b8SPaul E. McKenney #include <linux/init.h> 14*1253b9b8SPaul E. McKenney #include <linux/module.h> 15*1253b9b8SPaul E. McKenney #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */ 16*1253b9b8SPaul E. McKenney #include <linux/tick.h> 17*1253b9b8SPaul E. McKenney #include <linux/kthread.h> 18*1253b9b8SPaul E. McKenney #include <linux/delay.h> 19*1253b9b8SPaul E. McKenney #include <linux/prandom.h> 20*1253b9b8SPaul E. McKenney #include <linux/cpu.h> 21*1253b9b8SPaul E. McKenney 22*1253b9b8SPaul E. McKenney MODULE_LICENSE("GPL"); 23*1253b9b8SPaul E. McKenney MODULE_AUTHOR("Paul E. McKenney <paulmck@kernel.org>"); 24*1253b9b8SPaul E. McKenney 25*1253b9b8SPaul E. McKenney static int holdoff = IS_BUILTIN(CONFIG_TEST_CLOCKSOURCE_WATCHDOG) ? 10 : 0; 26*1253b9b8SPaul E. McKenney module_param(holdoff, int, 0444); 27*1253b9b8SPaul E. McKenney MODULE_PARM_DESC(holdoff, "Time to wait to start test (s)."); 28*1253b9b8SPaul E. McKenney 29*1253b9b8SPaul E. McKenney /* Watchdog kthread's task_struct pointer for debug purposes. */ 30*1253b9b8SPaul E. McKenney static struct task_struct *wdtest_task; 31*1253b9b8SPaul E. McKenney 32*1253b9b8SPaul E. McKenney static u64 wdtest_jiffies_read(struct clocksource *cs) 33*1253b9b8SPaul E. McKenney { 34*1253b9b8SPaul E. McKenney return (u64)jiffies; 35*1253b9b8SPaul E. McKenney } 36*1253b9b8SPaul E. McKenney 37*1253b9b8SPaul E. McKenney /* Assume HZ > 100. */ 38*1253b9b8SPaul E. McKenney #define JIFFIES_SHIFT 8 39*1253b9b8SPaul E. McKenney 40*1253b9b8SPaul E. McKenney static struct clocksource clocksource_wdtest_jiffies = { 41*1253b9b8SPaul E. McKenney .name = "wdtest-jiffies", 42*1253b9b8SPaul E. McKenney .rating = 1, /* lowest valid rating*/ 43*1253b9b8SPaul E. McKenney .uncertainty_margin = TICK_NSEC, 44*1253b9b8SPaul E. McKenney .read = wdtest_jiffies_read, 45*1253b9b8SPaul E. McKenney .mask = CLOCKSOURCE_MASK(32), 46*1253b9b8SPaul E. McKenney .flags = CLOCK_SOURCE_MUST_VERIFY, 47*1253b9b8SPaul E. McKenney .mult = TICK_NSEC << JIFFIES_SHIFT, /* details above */ 48*1253b9b8SPaul E. McKenney .shift = JIFFIES_SHIFT, 49*1253b9b8SPaul E. McKenney .max_cycles = 10, 50*1253b9b8SPaul E. McKenney }; 51*1253b9b8SPaul E. McKenney 52*1253b9b8SPaul E. McKenney static int wdtest_ktime_read_ndelays; 53*1253b9b8SPaul E. McKenney static bool wdtest_ktime_read_fuzz; 54*1253b9b8SPaul E. McKenney 55*1253b9b8SPaul E. McKenney static u64 wdtest_ktime_read(struct clocksource *cs) 56*1253b9b8SPaul E. McKenney { 57*1253b9b8SPaul E. McKenney int wkrn = READ_ONCE(wdtest_ktime_read_ndelays); 58*1253b9b8SPaul E. McKenney static int sign = 1; 59*1253b9b8SPaul E. McKenney u64 ret; 60*1253b9b8SPaul E. McKenney 61*1253b9b8SPaul E. McKenney if (wkrn) { 62*1253b9b8SPaul E. McKenney udelay(cs->uncertainty_margin / 250); 63*1253b9b8SPaul E. McKenney WRITE_ONCE(wdtest_ktime_read_ndelays, wkrn - 1); 64*1253b9b8SPaul E. McKenney } 65*1253b9b8SPaul E. McKenney ret = ktime_get_real_fast_ns(); 66*1253b9b8SPaul E. McKenney if (READ_ONCE(wdtest_ktime_read_fuzz)) { 67*1253b9b8SPaul E. McKenney sign = -sign; 68*1253b9b8SPaul E. McKenney ret = ret + sign * 100 * NSEC_PER_MSEC; 69*1253b9b8SPaul E. McKenney } 70*1253b9b8SPaul E. McKenney return ret; 71*1253b9b8SPaul E. McKenney } 72*1253b9b8SPaul E. McKenney 73*1253b9b8SPaul E. McKenney static void wdtest_ktime_cs_mark_unstable(struct clocksource *cs) 74*1253b9b8SPaul E. McKenney { 75*1253b9b8SPaul E. McKenney pr_info("--- Marking %s unstable due to clocksource watchdog.\n", cs->name); 76*1253b9b8SPaul E. McKenney } 77*1253b9b8SPaul E. McKenney 78*1253b9b8SPaul E. McKenney #define KTIME_FLAGS (CLOCK_SOURCE_IS_CONTINUOUS | \ 79*1253b9b8SPaul E. McKenney CLOCK_SOURCE_VALID_FOR_HRES | \ 80*1253b9b8SPaul E. McKenney CLOCK_SOURCE_MUST_VERIFY | \ 81*1253b9b8SPaul E. McKenney CLOCK_SOURCE_VERIFY_PERCPU) 82*1253b9b8SPaul E. McKenney 83*1253b9b8SPaul E. McKenney static struct clocksource clocksource_wdtest_ktime = { 84*1253b9b8SPaul E. McKenney .name = "wdtest-ktime", 85*1253b9b8SPaul E. McKenney .rating = 300, 86*1253b9b8SPaul E. McKenney .read = wdtest_ktime_read, 87*1253b9b8SPaul E. McKenney .mask = CLOCKSOURCE_MASK(64), 88*1253b9b8SPaul E. McKenney .flags = KTIME_FLAGS, 89*1253b9b8SPaul E. McKenney .mark_unstable = wdtest_ktime_cs_mark_unstable, 90*1253b9b8SPaul E. McKenney .list = LIST_HEAD_INIT(clocksource_wdtest_ktime.list), 91*1253b9b8SPaul E. McKenney }; 92*1253b9b8SPaul E. McKenney 93*1253b9b8SPaul E. McKenney /* Reset the clocksource if needed. */ 94*1253b9b8SPaul E. McKenney static void wdtest_ktime_clocksource_reset(void) 95*1253b9b8SPaul E. McKenney { 96*1253b9b8SPaul E. McKenney if (clocksource_wdtest_ktime.flags & CLOCK_SOURCE_UNSTABLE) { 97*1253b9b8SPaul E. McKenney clocksource_unregister(&clocksource_wdtest_ktime); 98*1253b9b8SPaul E. McKenney clocksource_wdtest_ktime.flags = KTIME_FLAGS; 99*1253b9b8SPaul E. McKenney schedule_timeout_uninterruptible(HZ / 10); 100*1253b9b8SPaul E. McKenney clocksource_register_khz(&clocksource_wdtest_ktime, 1000 * 1000); 101*1253b9b8SPaul E. McKenney } 102*1253b9b8SPaul E. McKenney } 103*1253b9b8SPaul E. McKenney 104*1253b9b8SPaul E. McKenney /* Run the specified series of watchdog tests. */ 105*1253b9b8SPaul E. McKenney static int wdtest_func(void *arg) 106*1253b9b8SPaul E. McKenney { 107*1253b9b8SPaul E. McKenney unsigned long j1, j2; 108*1253b9b8SPaul E. McKenney char *s; 109*1253b9b8SPaul E. McKenney int i; 110*1253b9b8SPaul E. McKenney 111*1253b9b8SPaul E. McKenney schedule_timeout_uninterruptible(holdoff * HZ); 112*1253b9b8SPaul E. McKenney 113*1253b9b8SPaul E. McKenney /* 114*1253b9b8SPaul E. McKenney * Verify that jiffies-like clocksources get the manually 115*1253b9b8SPaul E. McKenney * specified uncertainty margin. 116*1253b9b8SPaul E. McKenney */ 117*1253b9b8SPaul E. McKenney pr_info("--- Verify jiffies-like uncertainty margin.\n"); 118*1253b9b8SPaul E. McKenney __clocksource_register(&clocksource_wdtest_jiffies); 119*1253b9b8SPaul E. McKenney WARN_ON_ONCE(clocksource_wdtest_jiffies.uncertainty_margin != TICK_NSEC); 120*1253b9b8SPaul E. McKenney 121*1253b9b8SPaul E. McKenney j1 = clocksource_wdtest_jiffies.read(&clocksource_wdtest_jiffies); 122*1253b9b8SPaul E. McKenney schedule_timeout_uninterruptible(HZ); 123*1253b9b8SPaul E. McKenney j2 = clocksource_wdtest_jiffies.read(&clocksource_wdtest_jiffies); 124*1253b9b8SPaul E. McKenney WARN_ON_ONCE(j1 == j2); 125*1253b9b8SPaul E. McKenney 126*1253b9b8SPaul E. McKenney clocksource_unregister(&clocksource_wdtest_jiffies); 127*1253b9b8SPaul E. McKenney 128*1253b9b8SPaul E. McKenney /* 129*1253b9b8SPaul E. McKenney * Verify that tsc-like clocksources are assigned a reasonable 130*1253b9b8SPaul E. McKenney * uncertainty margin. 131*1253b9b8SPaul E. McKenney */ 132*1253b9b8SPaul E. McKenney pr_info("--- Verify tsc-like uncertainty margin.\n"); 133*1253b9b8SPaul E. McKenney clocksource_register_khz(&clocksource_wdtest_ktime, 1000 * 1000); 134*1253b9b8SPaul E. McKenney WARN_ON_ONCE(clocksource_wdtest_ktime.uncertainty_margin < NSEC_PER_USEC); 135*1253b9b8SPaul E. McKenney 136*1253b9b8SPaul E. McKenney j1 = clocksource_wdtest_ktime.read(&clocksource_wdtest_ktime); 137*1253b9b8SPaul E. McKenney udelay(1); 138*1253b9b8SPaul E. McKenney j2 = clocksource_wdtest_ktime.read(&clocksource_wdtest_ktime); 139*1253b9b8SPaul E. McKenney pr_info("--- tsc-like times: %lu - %lu = %lu.\n", j2, j1, j2 - j1); 140*1253b9b8SPaul E. McKenney WARN_ON_ONCE(time_before(j2, j1 + NSEC_PER_USEC)); 141*1253b9b8SPaul E. McKenney 142*1253b9b8SPaul E. McKenney /* Verify tsc-like stability with various numbers of errors injected. */ 143*1253b9b8SPaul E. McKenney for (i = 0; i <= max_cswd_read_retries + 1; i++) { 144*1253b9b8SPaul E. McKenney if (i <= 1 && i < max_cswd_read_retries) 145*1253b9b8SPaul E. McKenney s = ""; 146*1253b9b8SPaul E. McKenney else if (i <= max_cswd_read_retries) 147*1253b9b8SPaul E. McKenney s = ", expect message"; 148*1253b9b8SPaul E. McKenney else 149*1253b9b8SPaul E. McKenney s = ", expect clock skew"; 150*1253b9b8SPaul E. McKenney pr_info("--- Watchdog with %dx error injection, %lu retries%s.\n", i, max_cswd_read_retries, s); 151*1253b9b8SPaul E. McKenney WRITE_ONCE(wdtest_ktime_read_ndelays, i); 152*1253b9b8SPaul E. McKenney schedule_timeout_uninterruptible(2 * HZ); 153*1253b9b8SPaul E. McKenney WARN_ON_ONCE(READ_ONCE(wdtest_ktime_read_ndelays)); 154*1253b9b8SPaul E. McKenney WARN_ON_ONCE((i <= max_cswd_read_retries) != 155*1253b9b8SPaul E. McKenney !(clocksource_wdtest_ktime.flags & CLOCK_SOURCE_UNSTABLE)); 156*1253b9b8SPaul E. McKenney wdtest_ktime_clocksource_reset(); 157*1253b9b8SPaul E. McKenney } 158*1253b9b8SPaul E. McKenney 159*1253b9b8SPaul E. McKenney /* Verify tsc-like stability with clock-value-fuzz error injection. */ 160*1253b9b8SPaul E. McKenney pr_info("--- Watchdog clock-value-fuzz error injection, expect clock skew and per-CPU mismatches.\n"); 161*1253b9b8SPaul E. McKenney WRITE_ONCE(wdtest_ktime_read_fuzz, true); 162*1253b9b8SPaul E. McKenney schedule_timeout_uninterruptible(2 * HZ); 163*1253b9b8SPaul E. McKenney WARN_ON_ONCE(!(clocksource_wdtest_ktime.flags & CLOCK_SOURCE_UNSTABLE)); 164*1253b9b8SPaul E. McKenney clocksource_verify_percpu(&clocksource_wdtest_ktime); 165*1253b9b8SPaul E. McKenney WRITE_ONCE(wdtest_ktime_read_fuzz, false); 166*1253b9b8SPaul E. McKenney 167*1253b9b8SPaul E. McKenney clocksource_unregister(&clocksource_wdtest_ktime); 168*1253b9b8SPaul E. McKenney 169*1253b9b8SPaul E. McKenney pr_info("--- Done with test.\n"); 170*1253b9b8SPaul E. McKenney return 0; 171*1253b9b8SPaul E. McKenney } 172*1253b9b8SPaul E. McKenney 173*1253b9b8SPaul E. McKenney static void wdtest_print_module_parms(void) 174*1253b9b8SPaul E. McKenney { 175*1253b9b8SPaul E. McKenney pr_alert("--- holdoff=%d\n", holdoff); 176*1253b9b8SPaul E. McKenney } 177*1253b9b8SPaul E. McKenney 178*1253b9b8SPaul E. McKenney /* Cleanup function. */ 179*1253b9b8SPaul E. McKenney static void clocksource_wdtest_cleanup(void) 180*1253b9b8SPaul E. McKenney { 181*1253b9b8SPaul E. McKenney } 182*1253b9b8SPaul E. McKenney 183*1253b9b8SPaul E. McKenney static int __init clocksource_wdtest_init(void) 184*1253b9b8SPaul E. McKenney { 185*1253b9b8SPaul E. McKenney int ret = 0; 186*1253b9b8SPaul E. McKenney 187*1253b9b8SPaul E. McKenney wdtest_print_module_parms(); 188*1253b9b8SPaul E. McKenney 189*1253b9b8SPaul E. McKenney /* Create watchdog-test task. */ 190*1253b9b8SPaul E. McKenney wdtest_task = kthread_run(wdtest_func, NULL, "wdtest"); 191*1253b9b8SPaul E. McKenney if (IS_ERR(wdtest_task)) { 192*1253b9b8SPaul E. McKenney ret = PTR_ERR(wdtest_task); 193*1253b9b8SPaul E. McKenney pr_warn("%s: Failed to create wdtest kthread.\n", __func__); 194*1253b9b8SPaul E. McKenney wdtest_task = NULL; 195*1253b9b8SPaul E. McKenney return ret; 196*1253b9b8SPaul E. McKenney } 197*1253b9b8SPaul E. McKenney 198*1253b9b8SPaul E. McKenney return 0; 199*1253b9b8SPaul E. McKenney } 200*1253b9b8SPaul E. McKenney 201*1253b9b8SPaul E. McKenney module_init(clocksource_wdtest_init); 202*1253b9b8SPaul E. McKenney module_exit(clocksource_wdtest_cleanup); 203