Re: [patch] serial console vs NMI watchdog

From: Andrew Morton (andrewm@uow.edu.au)
Date: Fri Mar 09 2001 - 21:41:15 EST

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    Ion Badulescu wrote:
    >
    > On Sat, 10 Mar 2001 01:21:25 +1100, Andrew Morton <andrewm@uow.edu.au> wrote:
    >
    > > +/**
    > > + * enable_nmi_watchdog - enables/disables NMI watchdog checking.
    > > + * @yes: If zero, disable
    >
    > Ugh. I have a feeling that your chances to get Linus to accept this are
    > extremely slim.
    >
    > Just have two functions, enable_nmi_watchdog and disable_nmi_watchdog.
    > You can make them inline, or even macros...

    You're right.

    --- linux-2.4.2-ac16/include/linux/irq.h Fri Mar 9 17:11:17 2001
    +++ linux-ac/include/linux/irq.h Sat Mar 10 13:34:22 2001
    @@ -56,6 +56,21 @@
     
     #include <asm/hw_irq.h> /* the arch dependent stuff */
     
    +/**
    + * nmi_watchdog_disable - disable NMI watchdog checking.
    + *
    + * If the architecture supports the NMI watchdog, nmi_watchdog_disable() may be used
    + * to temporarily disable it. Use nmi_watchdog_enable() later on. It is implemented
    + * via an up/down counter, so you must keep the calls balanced.
    + */
    +#ifdef ARCH_HAS_NMI_WATCHDOG
    +extern void nmi_watchdog_disable(void);
    +extern void nmi_watchdog_enable(void);
    +#else
    +#define nmi_watchdog_disable() do{} while(0)
    +#define nmi_watchdog_enable() do{} while(0)
    +#endif
    +
     extern int handle_IRQ_event(unsigned int, struct pt_regs *, struct irqaction *);
     extern int setup_irq(unsigned int , struct irqaction * );
     
    --- linux-2.4.2-ac16/include/asm-i386/irq.h Fri Oct 8 03:17:09 1999
    +++ linux-ac/include/asm-i386/irq.h Sat Mar 10 02:17:47 2001
    @@ -32,4 +32,8 @@
     extern void disable_irq_nosync(unsigned int);
     extern void enable_irq(unsigned int);
     
    +#ifdef CONFIG_X86_LOCAL_APIC
    +#define ARCH_HAS_NMI_WATCHDOG /* See include/linux/irq.h */
    +#endif
    +
     #endif /* _ASM_IRQ_H */
    --- linux-2.4.2-ac16/drivers/char/sysrq.c Sun Feb 25 17:37:04 2001
    +++ linux-ac/drivers/char/sysrq.c Sat Mar 10 13:07:46 2001
    @@ -23,6 +23,7 @@
     #include <linux/quotaops.h>
     #include <linux/smp_lock.h>
     #include <linux/module.h>
    +#include <linux/irq.h>
     
     #include <asm/ptrace.h>
     
    @@ -69,6 +70,11 @@
             if (!key)
                     return;
     
    + /*
    + * Interrupts are disabled, and serial consoles are slow. So
    + * Let's suspend the NMI watchdog.
    + */
    + nmi_watchdog_disable();
             console_loglevel = 7;
             printk(KERN_INFO "SysRq: ");
             switch (key) {
    @@ -152,6 +158,7 @@
                     /* Don't use 'A' as it's handled specially on the Sparc */
             }
     
    + nmi_watchdog_enable();
             console_loglevel = orig_log_level;
     }
     
    --- linux-2.4.2-ac16/arch/i386/kernel/nmi.c Fri Mar 9 17:10:51 2001
    +++ linux-ac/arch/i386/kernel/nmi.c Sat Mar 10 13:21:59 2001
    @@ -226,6 +226,17 @@
     }
     
     static spinlock_t nmi_print_lock = SPIN_LOCK_UNLOCKED;
    +static atomic_t nmi_watchdog_disabled = ATOMIC_INIT(0);
    +
    +void nmi_watchdog_disable(void)
    +{
    + atomic_inc(&nmi_watchdog_disabled);
    +}
    +
    +void nmi_watchdog_enable(void)
    +{
    + atomic_dec(&nmi_watchdog_disabled);
    +}
     
     void nmi_watchdog_tick (struct pt_regs * regs)
     {
    @@ -255,7 +266,7 @@
     
             sum = apic_timer_irqs[cpu];
     
    - if (last_irq_sums[cpu] == sum) {
    + if (last_irq_sums[cpu] == sum && atomic_read(&nmi_watchdog_disabled) == 0) {
                     /*
                      * Ayiee, looks like this CPU is stuck ...
                      * wait a few IRQs (5 seconds) before doing the oops ...
    -
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