1 // SPDX-License-Identifier: GPL-2.0
3 #include <linux/cpu.h>
7 #include <linux/percpu-defs.h>
11 static unsigned int watchdog_next_cpu(unsigned int cpu)  in watchdog_next_cpu()  argument
15 	next_cpu = cpumask_next(cpu, &watchdog_cpus);  in watchdog_next_cpu()
19 	if (next_cpu == cpu)  in watchdog_next_cpu()
30 void watchdog_hardlockup_enable(unsigned int cpu)  in watchdog_hardlockup_enable()  argument
35 	 * The new CPU will be marked online before the hrtimer interrupt  in watchdog_hardlockup_enable()
36 	 * gets a chance to run on it. If another CPU tests for a  in watchdog_hardlockup_enable()
37 	 * hardlockup on the new CPU before it has run its the hrtimer  in watchdog_hardlockup_enable()
39 	 * the new CPU to delay the check for at least 3 sampling periods  in watchdog_hardlockup_enable()
40 	 * to guarantee one hrtimer has run on the new CPU.  in watchdog_hardlockup_enable()
42 	watchdog_hardlockup_touch_cpu(cpu);  in watchdog_hardlockup_enable()
45 	 * We are going to check the next CPU. Our watchdog_hrtimer  in watchdog_hardlockup_enable()
46 	 * need not be zero if the CPU has already been online earlier.  in watchdog_hardlockup_enable()
47 	 * Touch the watchdog on the next CPU to avoid false positive  in watchdog_hardlockup_enable()
48 	 * if we try to check it in less then 3 interrupts.  in watchdog_hardlockup_enable()
50 	next_cpu = watchdog_next_cpu(cpu);  in watchdog_hardlockup_enable()
55 	 * Makes sure that watchdog is touched on this CPU before  in watchdog_hardlockup_enable()
61 	cpumask_set_cpu(cpu, &watchdog_cpus);  in watchdog_hardlockup_enable()
64 void watchdog_hardlockup_disable(unsigned int cpu)  in watchdog_hardlockup_disable()  argument
66 	unsigned int next_cpu = watchdog_next_cpu(cpu);  in watchdog_hardlockup_disable()
69 	 * Offlining this CPU will cause the CPU before this one to start  in watchdog_hardlockup_disable()
70 	 * checking the one after this one. If this CPU just finished checking  in watchdog_hardlockup_disable()
71 	 * the next CPU and updating hrtimer_interrupts_saved, and then the  in watchdog_hardlockup_disable()
72 	 * previous CPU checks it within one sample period, it will trigger a  in watchdog_hardlockup_disable()
73 	 * false positive. Touch the watchdog on the next CPU to prevent it.  in watchdog_hardlockup_disable()
79 	 * Makes sure that watchdog is touched on the next CPU before  in watchdog_hardlockup_disable()
80 	 * this CPU disappear in watchdog_cpus. The counter part is in  in watchdog_hardlockup_disable()
85 	cpumask_clear_cpu(cpu, &watchdog_cpus);  in watchdog_hardlockup_disable()
93 	 * Test for hardlockups every 3 samples. The sample period is  in watchdog_buddy_check_hardlockup()
94 	 *  watchdog_thresh * 2 / 5, so 3 samples gets us back to slightly over  in watchdog_buddy_check_hardlockup()
97 	if (hrtimer_interrupts % 3 != 0)  in watchdog_buddy_check_hardlockup()
100 	/* check for a hardlockup on the next CPU */  in watchdog_buddy_check_hardlockup()
106 	 * Make sure that the watchdog was touched on next CPU when  in watchdog_buddy_check_hardlockup()