1 // SPDX-License-Identifier: GPL-2.0
3  * Detect hard and soft lockups on a system
9  * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
63  * Should we panic when a soft-lockup or hard-lockup occurs:
205 		 * Prevent multiple hard-lockup reports if one cpu is already  in watchdog_hardlockup_check()
261  * watchdog_hardlockup_enable/disable can be implemented to start and stop when
262  * softlockup watchdog start and stop. The detector must select the
270  * Watchdog-detector specific API.
278 	return -ENODEV;  in watchdog_hardlockup_probe()
282  * watchdog_hardlockup_stop - Stop the watchdog for reconfiguration
292  * watchdog_hardlockup_start - Start the watchdog after reconfiguration
298  * - watchdog_enabled
299  * - watchdog_thresh
300  * - watchdog_cpumask
305  * lockup_detector_update_enable - Update the sysctl enable bit
450 		util = DIV_ROUND_UP(100 * (new_stat - old_stat), sample_period_16);  in update_cpustat()
452 		 * Since we use 16-bit precision, the raw data will undergo  in update_cpustat()
517  * would be useful to start interrupt counting.
524 	tail = (tail + NUM_HARDIRQ_REPORT - 1) % NUM_HARDIRQ_REPORT;  in need_counting_irqs()
546 		{-1, 0}, {-1, 0}, {-1, 0}, {-1, 0}, {-1, 0}  in print_irq_counts()
564 			if (irq_counts_sorted[i].irq == -1)  in print_irq_counts()
567 			printk(KERN_CRIT "\t#%u: %-10u\tirq#%d\n",  in print_irq_counts()
595  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
597  * want a higher threshold for soft lockups than for hard lockups. So we couple
598  * the thresholds with a factor: we make the soft threshold twice the amount of
621 	 * or three with the current relation between the soft  in set_sample_period()
642  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
645  * preventing the watchdog task from executing - e.g. the scheduler
671 	 * from (soft)interrupt context, so the access to  in touch_all_softlockup_watchdogs()
708 		 * A poorly behaving BPF scheduler can live-lock the system into  in is_softlockup()
709 		 * soft lockups. Tell sched_ext to try ejecting the BPF  in is_softlockup()
710 		 * scheduler when close to a soft lockup.  in is_softlockup()
713 			scx_softlockup(now - touch_ts);  in is_softlockup()
717 			return now - touch_ts;  in is_softlockup()
727  * The watchdog feed function - touches the timestamp.
731  * for more than 2*watchdog_thresh seconds then the debug-printout
782 	 * the watchdog like a soft lockup. This function touches the watchdog.  in watchdog_timer_fn()
818 		 * Prevent multiple soft-lockup reports if one cpu is already  in watchdog_timer_fn()
826 		/* Start period for the next softlockup warning. */  in watchdog_timer_fn()
830 		pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",  in watchdog_timer_fn()
832 			current->comm, task_pid_nr(current));  in watchdog_timer_fn()
867 	 * Start the timer first to prevent the hardlockup watchdog triggering  in watchdog_enable()
1018  * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
1041  * caller             | table->data points to            | 'which'
1042  * -------------------|----------------------------------|-------------------------------
1045  * -------------------|----------------------------------|-------------------------------
1047  * -------------------|----------------------------------|-------------------------------
1053 	int err, old, *param = table->data;  in proc_watchdog_common()
1093 		return -ENOTSUPP;  in proc_nmi_watchdog()
1273 		if (ret == -ENODEV)  in lockup_detector_delay_init()
1288  * lockup_detector_retry_init - retry init lockup detector if possible.