// SPDX-License-Identifier: GPL-2.0-only/* * hangcheck-timer.c * * Driver for a little io fencing timer. * * Copyright (C) 2002, 2003 Oracle.  All rights reserved. * * Author: Joel Becker <joel.becker@oracle.com> */ /* * The hangcheck-timer driver uses the TSC to catch delays that * jiffies does not notice.  A timer is set.  When the timer fires, it * checks whether it was delayed and if that delay exceeds a given * margin of error.  The hangcheck_tick module parameter takes the timer * duration in seconds.  The hangcheck_margin parameter defines the * margin of error, in seconds.  The defaults are 60 seconds for the * timer and 180 seconds for the margin of error.  IOW, a timer is set * for 60 seconds.  When the timer fires, the callback checks the * actual duration that the timer waited.  If the duration exceeds the * allotted time and margin (here 60 + 180, or 240 seconds), the machine * is restarted.  A healthy machine will have the duration match the * expected timeout very closely. */ #include <linux/module.h>#include <linux/moduleparam.h>#include <linux/types.h>#include <linux/kernel.h>#include <linux/fs.h>#include <linux/mm.h>#include <linux/reboot.h>#include <linux/init.h>#include <linux/delay.h>#include <linux/uaccess.h>#include <linux/sysrq.h>#include <linux/timer.h>#include <linux/hrtimer.h> #define VERSION_STR "0.9.1" #define DEFAULT_IOFENCE_MARGIN 60	/* Default fudge factor, in seconds */#define DEFAULT_IOFENCE_TICK 180	/* Default timer timeout, in seconds */ static int hangcheck_tick = DEFAULT_IOFENCE_TICK;static int hangcheck_margin = DEFAULT_IOFENCE_MARGIN;static int hangcheck_reboot;  /* Defaults to not reboot */static int hangcheck_dump_tasks;  /* Defaults to not dumping SysRQ T */ /* options - modular */module_param(hangcheck_tick, int, 0);MODULE_PARM_DESC(hangcheck_tick, "Timer delay.");module_param(hangcheck_margin, int, 0);MODULE_PARM_DESC(hangcheck_margin, "If the hangcheck timer has been delayed more than hangcheck_margin seconds, the driver will fire.");module_param(hangcheck_reboot, int, 0);MODULE_PARM_DESC(hangcheck_reboot, "If nonzero, the machine will reboot when the timer margin is exceeded.");module_param(hangcheck_dump_tasks, int, 0);MODULE_PARM_DESC(hangcheck_dump_tasks, "If nonzero, the machine will dump the system task state when the timer margin is exceeded."); MODULE_AUTHOR("Oracle");MODULE_DESCRIPTION("Hangcheck-timer detects when the system has gone out to lunch past a certain margin.");MODULE_LICENSE("GPL");MODULE_VERSION(VERSION_STR); /* options - nonmodular */#ifndef MODULE static int __init hangcheck_parse_tick(char *str){	int par; 	if (get_option(&str, &par))		hangcheck_tick = par;	return 1;} static int __init hangcheck_parse_margin(char *str){	int par; 	if (get_option(&str, &par))		hangcheck_margin = par;	return 1;} static int __init hangcheck_parse_reboot(char *str){	int par; 	if (get_option(&str, &par))		hangcheck_reboot = par;	return 1;} static int __init hangcheck_parse_dump_tasks(char *str){	int par; 	if (get_option(&str, &par))		hangcheck_dump_tasks = par;	return 1;} __setup("hcheck_tick", hangcheck_parse_tick);__setup("hcheck_margin", hangcheck_parse_margin);__setup("hcheck_reboot", hangcheck_parse_reboot);__setup("hcheck_dump_tasks", hangcheck_parse_dump_tasks);#endif /* not MODULE */ #define TIMER_FREQ 1000000000ULL /* Last time scheduled */static unsigned long long hangcheck_tsc, hangcheck_tsc_margin; static void hangcheck_fire(struct timer_list *); static DEFINE_TIMER(hangcheck_ticktock, hangcheck_fire); static void hangcheck_fire(struct timer_list *unused){	unsigned long long cur_tsc, tsc_diff; 	cur_tsc = ktime_get_ns(); 	if (cur_tsc > hangcheck_tsc)		tsc_diff = cur_tsc - hangcheck_tsc;	else		tsc_diff = (cur_tsc + (~0ULL - hangcheck_tsc)); /* or something */ 	if (tsc_diff > hangcheck_tsc_margin) {		if (hangcheck_dump_tasks) {			pr_crit("Hangcheck: Task state:\n");#ifdef CONFIG_MAGIC_SYSRQ			handle_sysrq('t');#endif  /* CONFIG_MAGIC_SYSRQ */		}		if (hangcheck_reboot) {			pr_crit("Hangcheck: hangcheck is restarting the machine.\n");			emergency_restart();		} else {			pr_crit("Hangcheck: hangcheck value past margin!\n");		}	}#if 0	/*	 * Enable to investigate delays in detail	 */	pr_debug("Hangcheck: called %lld ns since last time (%lld ns overshoot)\n",			tsc_diff, tsc_diff - hangcheck_tick*TIMER_FREQ);#endif	mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ));	hangcheck_tsc = ktime_get_ns();}  static int __init hangcheck_init(void){	pr_debug("Hangcheck: starting hangcheck timer %s (tick is %d seconds, margin is %d seconds).\n",	       VERSION_STR, hangcheck_tick, hangcheck_margin);	hangcheck_tsc_margin =		(unsigned long long)hangcheck_margin + hangcheck_tick;	hangcheck_tsc_margin *= TIMER_FREQ; 	hangcheck_tsc = ktime_get_ns();	mod_timer(&hangcheck_ticktock, jiffies + (hangcheck_tick*HZ)); 	return 0;}  static void __exit hangcheck_exit(void){	timer_delete_sync(&hangcheck_ticktock);	pr_debug("Hangcheck: Stopped hangcheck timer.\n");} module_init(hangcheck_init);module_exit(hangcheck_exit);