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![Rusty Russell](/assets/img/avatar_default.png)
Impact: Reduce stack usage, use new cpumask API. Mainly changing cpumask_t to 'struct cpumask' and similar simple API conversion. Two conversions worth mentioning: 1) we use cpumask_any_but to avoid a temporary in kernel/softlockup.c, 2) Use cpumask_var_t in taskstats_user_cmd(). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@redhat.com>
369 lines
8.8 KiB
C
369 lines
8.8 KiB
C
/*
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* Detect Soft Lockups
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*
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* started by Ingo Molnar, Copyright (C) 2005, 2006 Red Hat, Inc.
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*
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* this code detects soft lockups: incidents in where on a CPU
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* the kernel does not reschedule for 10 seconds or more.
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*/
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#include <linux/mm.h>
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#include <linux/cpu.h>
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#include <linux/nmi.h>
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#include <linux/init.h>
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#include <linux/delay.h>
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#include <linux/freezer.h>
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#include <linux/kthread.h>
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#include <linux/lockdep.h>
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#include <linux/notifier.h>
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#include <linux/module.h>
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#include <asm/irq_regs.h>
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static DEFINE_SPINLOCK(print_lock);
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static DEFINE_PER_CPU(unsigned long, touch_timestamp);
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static DEFINE_PER_CPU(unsigned long, print_timestamp);
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static DEFINE_PER_CPU(struct task_struct *, watchdog_task);
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static int __read_mostly did_panic;
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int __read_mostly softlockup_thresh = 60;
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/*
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* Should we panic (and reboot, if panic_timeout= is set) when a
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* soft-lockup occurs:
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*/
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unsigned int __read_mostly softlockup_panic =
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CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
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static int __init softlockup_panic_setup(char *str)
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{
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softlockup_panic = simple_strtoul(str, NULL, 0);
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return 1;
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}
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__setup("softlockup_panic=", softlockup_panic_setup);
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static int
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softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)
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{
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did_panic = 1;
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return NOTIFY_DONE;
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}
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static struct notifier_block panic_block = {
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.notifier_call = softlock_panic,
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};
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/*
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* Returns seconds, approximately. We don't need nanosecond
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* resolution, and we don't need to waste time with a big divide when
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* 2^30ns == 1.074s.
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*/
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static unsigned long get_timestamp(int this_cpu)
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{
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return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */
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}
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static void __touch_softlockup_watchdog(void)
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{
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int this_cpu = raw_smp_processor_id();
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__raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu);
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}
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void touch_softlockup_watchdog(void)
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{
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__raw_get_cpu_var(touch_timestamp) = 0;
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}
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EXPORT_SYMBOL(touch_softlockup_watchdog);
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void touch_all_softlockup_watchdogs(void)
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{
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int cpu;
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/* Cause each CPU to re-update its timestamp rather than complain */
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for_each_online_cpu(cpu)
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per_cpu(touch_timestamp, cpu) = 0;
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}
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EXPORT_SYMBOL(touch_all_softlockup_watchdogs);
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/*
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* This callback runs from the timer interrupt, and checks
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* whether the watchdog thread has hung or not:
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*/
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void softlockup_tick(void)
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{
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int this_cpu = smp_processor_id();
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unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu);
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unsigned long print_timestamp;
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struct pt_regs *regs = get_irq_regs();
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unsigned long now;
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/* Is detection switched off? */
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if (!per_cpu(watchdog_task, this_cpu) || softlockup_thresh <= 0) {
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/* Be sure we don't false trigger if switched back on */
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if (touch_timestamp)
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per_cpu(touch_timestamp, this_cpu) = 0;
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return;
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}
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if (touch_timestamp == 0) {
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__touch_softlockup_watchdog();
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return;
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}
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print_timestamp = per_cpu(print_timestamp, this_cpu);
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/* report at most once a second */
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if (print_timestamp == touch_timestamp || did_panic)
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return;
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/* do not print during early bootup: */
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if (unlikely(system_state != SYSTEM_RUNNING)) {
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__touch_softlockup_watchdog();
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return;
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}
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now = get_timestamp(this_cpu);
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/*
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* Wake up the high-prio watchdog task twice per
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* threshold timespan.
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*/
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if (now > touch_timestamp + softlockup_thresh/2)
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wake_up_process(per_cpu(watchdog_task, this_cpu));
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/* Warn about unreasonable delays: */
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if (now <= (touch_timestamp + softlockup_thresh))
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return;
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per_cpu(print_timestamp, this_cpu) = touch_timestamp;
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spin_lock(&print_lock);
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printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n",
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this_cpu, now - touch_timestamp,
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current->comm, task_pid_nr(current));
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print_modules();
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print_irqtrace_events(current);
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if (regs)
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show_regs(regs);
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else
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dump_stack();
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spin_unlock(&print_lock);
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if (softlockup_panic)
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panic("softlockup: hung tasks");
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}
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/*
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* Have a reasonable limit on the number of tasks checked:
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*/
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unsigned long __read_mostly sysctl_hung_task_check_count = 1024;
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/*
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* Zero means infinite timeout - no checking done:
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*/
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unsigned long __read_mostly sysctl_hung_task_timeout_secs = 480;
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unsigned long __read_mostly sysctl_hung_task_warnings = 10;
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/*
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* Only do the hung-tasks check on one CPU:
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*/
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static int check_cpu __read_mostly = -1;
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static void check_hung_task(struct task_struct *t, unsigned long now)
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{
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unsigned long switch_count = t->nvcsw + t->nivcsw;
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if (t->flags & PF_FROZEN)
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return;
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if (switch_count != t->last_switch_count || !t->last_switch_timestamp) {
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t->last_switch_count = switch_count;
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t->last_switch_timestamp = now;
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return;
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}
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if ((long)(now - t->last_switch_timestamp) <
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sysctl_hung_task_timeout_secs)
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return;
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if (!sysctl_hung_task_warnings)
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return;
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sysctl_hung_task_warnings--;
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/*
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* Ok, the task did not get scheduled for more than 2 minutes,
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* complain:
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*/
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printk(KERN_ERR "INFO: task %s:%d blocked for more than "
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"%ld seconds.\n", t->comm, t->pid,
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sysctl_hung_task_timeout_secs);
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printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
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" disables this message.\n");
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sched_show_task(t);
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__debug_show_held_locks(t);
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t->last_switch_timestamp = now;
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touch_nmi_watchdog();
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if (softlockup_panic)
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panic("softlockup: blocked tasks");
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}
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/*
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* Check whether a TASK_UNINTERRUPTIBLE does not get woken up for
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* a really long time (120 seconds). If that happens, print out
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* a warning.
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*/
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static void check_hung_uninterruptible_tasks(int this_cpu)
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{
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int max_count = sysctl_hung_task_check_count;
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unsigned long now = get_timestamp(this_cpu);
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struct task_struct *g, *t;
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/*
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* If the system crashed already then all bets are off,
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* do not report extra hung tasks:
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*/
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if (test_taint(TAINT_DIE) || did_panic)
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return;
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read_lock(&tasklist_lock);
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do_each_thread(g, t) {
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if (!--max_count)
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goto unlock;
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/* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */
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if (t->state == TASK_UNINTERRUPTIBLE)
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check_hung_task(t, now);
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} while_each_thread(g, t);
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unlock:
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read_unlock(&tasklist_lock);
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}
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/*
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* The watchdog thread - runs every second and touches the timestamp.
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*/
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static int watchdog(void *__bind_cpu)
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{
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struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
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int this_cpu = (long)__bind_cpu;
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sched_setscheduler(current, SCHED_FIFO, ¶m);
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/* initialize timestamp */
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__touch_softlockup_watchdog();
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set_current_state(TASK_INTERRUPTIBLE);
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/*
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* Run briefly once per second to reset the softlockup timestamp.
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* If this gets delayed for more than 60 seconds then the
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* debug-printout triggers in softlockup_tick().
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*/
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while (!kthread_should_stop()) {
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__touch_softlockup_watchdog();
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schedule();
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if (kthread_should_stop())
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break;
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if (this_cpu == check_cpu) {
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if (sysctl_hung_task_timeout_secs)
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check_hung_uninterruptible_tasks(this_cpu);
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}
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set_current_state(TASK_INTERRUPTIBLE);
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}
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__set_current_state(TASK_RUNNING);
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return 0;
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}
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/*
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* Create/destroy watchdog threads as CPUs come and go:
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*/
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static int __cpuinit
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cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
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{
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int hotcpu = (unsigned long)hcpu;
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struct task_struct *p;
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switch (action) {
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case CPU_UP_PREPARE:
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case CPU_UP_PREPARE_FROZEN:
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BUG_ON(per_cpu(watchdog_task, hotcpu));
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p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu);
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if (IS_ERR(p)) {
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printk(KERN_ERR "watchdog for %i failed\n", hotcpu);
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return NOTIFY_BAD;
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}
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per_cpu(touch_timestamp, hotcpu) = 0;
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per_cpu(watchdog_task, hotcpu) = p;
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kthread_bind(p, hotcpu);
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break;
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case CPU_ONLINE:
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case CPU_ONLINE_FROZEN:
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check_cpu = cpumask_any(cpu_online_mask);
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wake_up_process(per_cpu(watchdog_task, hotcpu));
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break;
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#ifdef CONFIG_HOTPLUG_CPU
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case CPU_DOWN_PREPARE:
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case CPU_DOWN_PREPARE_FROZEN:
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if (hotcpu == check_cpu) {
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/* Pick any other online cpu. */
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check_cpu = cpumask_any_but(cpu_online_mask, hotcpu);
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}
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break;
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case CPU_UP_CANCELED:
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case CPU_UP_CANCELED_FROZEN:
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if (!per_cpu(watchdog_task, hotcpu))
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break;
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/* Unbind so it can run. Fall thru. */
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kthread_bind(per_cpu(watchdog_task, hotcpu),
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cpumask_any(cpu_online_mask));
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case CPU_DEAD:
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case CPU_DEAD_FROZEN:
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p = per_cpu(watchdog_task, hotcpu);
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per_cpu(watchdog_task, hotcpu) = NULL;
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kthread_stop(p);
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break;
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#endif /* CONFIG_HOTPLUG_CPU */
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}
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return NOTIFY_OK;
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}
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static struct notifier_block __cpuinitdata cpu_nfb = {
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.notifier_call = cpu_callback
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};
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static int __initdata nosoftlockup;
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static int __init nosoftlockup_setup(char *str)
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{
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nosoftlockup = 1;
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return 1;
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}
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__setup("nosoftlockup", nosoftlockup_setup);
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static int __init spawn_softlockup_task(void)
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{
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void *cpu = (void *)(long)smp_processor_id();
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int err;
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if (nosoftlockup)
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return 0;
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err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
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if (err == NOTIFY_BAD) {
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BUG();
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return 1;
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}
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cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
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register_cpu_notifier(&cpu_nfb);
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atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
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return 0;
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}
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early_initcall(spawn_softlockup_task);
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