forked from Minki/linux
554ec06398
The spin_lock_debug/rcu_cpu_stall detector uses
trigger_all_cpu_backtrace() to dump cpu backtrace.
Therefore it is possible that trigger_all_cpu_backtrace()
could be called at the same time on different CPUs, which
triggers and 'unknown reason NMI' warning. The following case
illustrates the problem:
CPU1 CPU2 ... CPU N
trigger_all_cpu_backtrace()
set "backtrace_mask" to cpu mask
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generate NMI interrupts generate NMI interrupts ...
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The "backtrace_mask" will be cleaned by the first NMI interrupt
at nmi_watchdog_tick(), then the following NMI interrupts
generated by other cpus's arch_trigger_all_cpu_backtrace() will
be taken as unknown reason NMI interrupts.
This patch uses a test_and_set to avoid the problem, and stop
the arch_trigger_all_cpu_backtrace() from calling to avoid
dumping a double cpu backtrace info when there is already a
trigger_all_cpu_backtrace() in progress.
Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>
Reviewed-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Cc: fweisbec@gmail.com
LKML-Reference: <1294198689-15447-2-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Don Zickus <dzickus@redhat.com>
109 lines
2.4 KiB
C
109 lines
2.4 KiB
C
/*
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* HW NMI watchdog support
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*
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* started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
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*
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* Arch specific calls to support NMI watchdog
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*
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* Bits copied from original nmi.c file
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*
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*/
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#include <asm/apic.h>
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#include <linux/cpumask.h>
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#include <linux/kdebug.h>
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#include <linux/notifier.h>
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#include <linux/kprobes.h>
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#include <linux/nmi.h>
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#include <linux/module.h>
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#ifdef CONFIG_HARDLOCKUP_DETECTOR
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u64 hw_nmi_get_sample_period(void)
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{
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return (u64)(cpu_khz) * 1000 * 60;
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}
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#endif
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#ifdef arch_trigger_all_cpu_backtrace
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/* For reliability, we're prepared to waste bits here. */
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static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
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/* "in progress" flag of arch_trigger_all_cpu_backtrace */
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static unsigned long backtrace_flag;
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void arch_trigger_all_cpu_backtrace(void)
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{
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int i;
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if (test_and_set_bit(0, &backtrace_flag))
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/*
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* If there is already a trigger_all_cpu_backtrace() in progress
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* (backtrace_flag == 1), don't output double cpu dump infos.
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*/
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return;
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cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask);
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printk(KERN_INFO "sending NMI to all CPUs:\n");
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apic->send_IPI_all(NMI_VECTOR);
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/* Wait for up to 10 seconds for all CPUs to do the backtrace */
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for (i = 0; i < 10 * 1000; i++) {
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if (cpumask_empty(to_cpumask(backtrace_mask)))
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break;
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mdelay(1);
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}
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clear_bit(0, &backtrace_flag);
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smp_mb__after_clear_bit();
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}
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static int __kprobes
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arch_trigger_all_cpu_backtrace_handler(struct notifier_block *self,
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unsigned long cmd, void *__args)
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{
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struct die_args *args = __args;
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struct pt_regs *regs;
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int cpu;
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switch (cmd) {
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case DIE_NMI:
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case DIE_NMI_IPI:
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break;
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default:
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return NOTIFY_DONE;
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}
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regs = args->regs;
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cpu = smp_processor_id();
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if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
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static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED;
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arch_spin_lock(&lock);
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printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
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show_regs(regs);
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dump_stack();
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arch_spin_unlock(&lock);
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cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
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return NOTIFY_STOP;
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}
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return NOTIFY_DONE;
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}
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static __read_mostly struct notifier_block backtrace_notifier = {
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.notifier_call = arch_trigger_all_cpu_backtrace_handler,
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.next = NULL,
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.priority = 1
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};
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static int __init register_trigger_all_cpu_backtrace(void)
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{
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register_die_notifier(&backtrace_notifier);
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return 0;
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}
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early_initcall(register_trigger_all_cpu_backtrace);
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#endif
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