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x86/nmi: Remove irq_work from the long duration NMI handler
First, printk() is NMI-context safe now since the safe printk() has been implemented and it already has an irq_work to make NMI-context safe. Second, this NMI irq_work actually does not work if a NMI handler causes panic by watchdog timeout. It has no chance to run in such case, while the safe printk() will flush its per-cpu buffers before panicking. While at it, repurpose the irq_work callback into a function which concentrates the NMI duration checking and makes the code easier to follow. [ bp: Massage. ] Signed-off-by: Changbin Du <changbin.du@gmail.com> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20200111125427.15662-1-changbin.du@gmail.com
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parent
36209766ce
commit
248ed51048
2 changed files with 9 additions and 12 deletions
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@ -41,7 +41,6 @@ struct nmiaction {
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struct list_head list;
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nmi_handler_t handler;
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u64 max_duration;
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struct irq_work irq_work;
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unsigned long flags;
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const char *name;
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};
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@ -104,18 +104,22 @@ static int __init nmi_warning_debugfs(void)
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}
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fs_initcall(nmi_warning_debugfs);
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static void nmi_max_handler(struct irq_work *w)
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static void nmi_check_duration(struct nmiaction *action, u64 duration)
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{
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struct nmiaction *a = container_of(w, struct nmiaction, irq_work);
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u64 whole_msecs = READ_ONCE(action->max_duration);
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int remainder_ns, decimal_msecs;
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u64 whole_msecs = READ_ONCE(a->max_duration);
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if (duration < nmi_longest_ns || duration < action->max_duration)
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return;
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action->max_duration = duration;
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remainder_ns = do_div(whole_msecs, (1000 * 1000));
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decimal_msecs = remainder_ns / 1000;
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printk_ratelimited(KERN_INFO
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"INFO: NMI handler (%ps) took too long to run: %lld.%03d msecs\n",
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a->handler, whole_msecs, decimal_msecs);
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action->handler, whole_msecs, decimal_msecs);
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}
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static int nmi_handle(unsigned int type, struct pt_regs *regs)
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@ -142,11 +146,7 @@ static int nmi_handle(unsigned int type, struct pt_regs *regs)
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delta = sched_clock() - delta;
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trace_nmi_handler(a->handler, (int)delta, thishandled);
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if (delta < nmi_longest_ns || delta < a->max_duration)
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continue;
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a->max_duration = delta;
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irq_work_queue(&a->irq_work);
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nmi_check_duration(a, delta);
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}
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rcu_read_unlock();
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@ -164,8 +164,6 @@ int __register_nmi_handler(unsigned int type, struct nmiaction *action)
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if (!action->handler)
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return -EINVAL;
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init_irq_work(&action->irq_work, nmi_max_handler);
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raw_spin_lock_irqsave(&desc->lock, flags);
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/*
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