在msm8610里，有一个debug选项LOCKUP_DETECTOR。之前有过说明。 在msm8916里，又多了CONFIG_MSM_WATCHDOG_V2 和CONFIG_HARDLOCKUP_DETECTOR_OTHER_CPU两个宏。 **CONFIG_MSM_WATCHDOG_V2后面再说，先说一下LOCKUP_DETECTOR和CONFIG_HARDLOCKUP_DETECTOR_OTHER_CPU。
下面来分析一下代码，然后看一下系统怎么检测soft lockup和hard lockup。
接下来我们从具体代码入手分析linux（3.10）是如何实现这两种lockup的探测的：
在初始化的时候会调用watchdog_enable()
static void watchdog_enable(unsigned int cpu){ struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer); /* kick off the timer for the hardlockup detector */ hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); hrtimer->function = watchdog_timer_fn; if (!watchdog_enabled) { kthread_park(current); return; } /* Enable the perf event */ watchdog_nmi_enable(cpu); /* done here because hrtimer_start can only pin to smp_processor_id() */ //每个cpu在启动的时候都会调用一次watchdog_enable()，然后每4秒就会调用一次watchdog_timer_fn hrtimer_start(hrtimer, ns_to_ktime(sample_period), HRTIMER_MODE_REL_PINNED); /* initialize timestamp */ watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1); __touch_watchdog();}然后第一次watchdog_enable运行之后，过4秒就会调用watchdog_timer_fn()。
static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer){ unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);//watchdog_touch_ts每次在 //__touch_watchdog里边会赋值成get_timestamp()，get_timestamp()函数在 //watchdog.c文件里边的定义，返回值是秒数！ //但touch_ts的值绝大多数时间都是0，因为touch_softlockup_watchdog()函数和 //touch_nmi_watchdog()频繁被调用，把watchdog_touch_ts的值赋值为0 //没有仔细看touch_softlockup_watchdog和touch_nmi_watchdog的调用点，但好像都是在 //调度的时候调用这两个函数去把watchdog_touch_ts清零的。 //如果这里发现touch_ts不是0，那表明上次watchdog被唤醒，一直到现在都没有调度，应该是有问题的。 //那怎么判断是否是真的有问题呢？继续往下看 struct pt_regs *regs = get_irq_regs(); int duration; pr_info("watchdog_timer_fn started/n"); /* kick the hardlockup detector */ watchdog_interrupt_count(); /* test for hardlockups on the next cpu */ watchdog_check_hardlockup_other_cpu();//这个先不管，后面再说明怎么检测其他cpu上是否有hardlock的 /* kick the softlockup detector */ wake_up_process(__this_cpu_read(softlockup_watchdog));//唤醒watchdog进程 //前面说过softlockup_watchdog这里保存watchdog相关的task_struct指针的指针， //所以这里用来唤醒watchdog的task。 /* .. and repeat */ hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));//延长当前hrtimer到期的时间！！ //使用这个函数，下一次hrtimer到期的时间是现在的时间加上ns_to_ktime(sample_period)这个时间！！ if (touch_ts == 0) { if (unlikely(__this_cpu_read(softlockup_touch_sync))) { /* * If the time stamp was touched atomically * make sure the scheduler tick is up to date. */ __this_cpu_write(softlockup_touch_sync, false); sched_clock_tick(); } /* Clear the guest paused flag on watchdog reset */ kvm_check_and_clear_guest_paused(); __touch_watchdog(); return HRTIMER_RESTART; } /* check for a softlockup * This is done by making sure a high priority task is * being scheduled. The task touches the watchdog to * indicate it is getting cpu time. If it hasn't then * this is a good indication some task is hogging the cpu */ //能跑到这里，像上面说的，上次watchdog进程被唤醒之后，到现在一直是没有调度的。 //但是怎么判断现在已经有问题呢?下面is_softlockup()函数判断，上次watchdog被唤醒到现在这段时间，是否大于20秒 //如果大于20秒，那就进入下面的if语句了，表明系统有问题。但具体是hardlock还是softlock还得判断一下 duration = is_softlockup(touch_ts); if (unlikely(duration)) { /* * If a virtual machine is stopped by the host it can look to * the watchdog like a soft lockup, check to see if the host * stopped the vm before we issue the warning */ if (kvm_check_and_clear_guest_paused()) return HRTIMER_RESTART; /* only warn once */ if (__this_cpu_read(soft_watchdog_warn) == true) return HRTIMER_RESTART; printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]/n", smp_processor_id(), duration, current->comm, task_pid_nr(current)); print_modules(); print_irqtrace_events(current); if (regs) show_regs(regs); else dump_stack(); if (softlockup_panic) panic("softlockup: hung tasks"); __this_cpu_write(soft_watchdog_warn, true); } else __this_cpu_write(soft_watchdog_warn, false); return HRTIMER_RESTART;//重新开始hrtimer！！和上面的 //hrtimer_forward_now函数配合，可以重新 //开始hrtimer并设置下一次运行的时间！！}新闻热点
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