5efa92f754
There is not that much use for it on a single CPU, however, deadlock between kernel and system task can be delected. Or a runaway loop. If a kernel gets locked up the timer interrupts don't occure (as all interrupts are disabled in kernel mode). The only chance is to interrupt the kernel by a non-maskable interrupt. This patch generates NMIs using performance counters. It uses the most widely available performace counters. As the performance counters are highly model-specific this patch is not guaranteed to work on every machine. Unfortunately this is also true for KVM :-/ On the other hand adding this feature for other models is not extremely difficult and the framework makes it hopefully easy enough. Depending on the frequency of the CPU an NMI is generated at most about every 0.5s If the cpu's speed is less then 2Ghz it is generated at most every 1s. In general an NMI is generated much less often as the performance counter counts down only if the cpu is not idle. Therefore the overhead of this feature is fairly minimal even if the load is high. Uppon detecting that the kernel is locked up the kernel dumps the state of the kernel registers and panics. Local APIC must be enabled for the watchdog to work. The code is _always_ compiled in, however, it is only enabled if watchdog=<non-zero> is set in the boot monitor. One corner case is serial console debugging. As dumping a lot of stuff to the serial link may take a lot of time, the watchdog does not detect lockups during this time!!! as it would result in too many false positives. 10 nmi have to be handled before the lockup is detected. This means something between ~5s to 10s. Another corner case is that the watchdog is enabled only after the paging is enabled as it would be pure madness to try to get it right.
56 lines
2 KiB
C
56 lines
2 KiB
C
#ifndef KERNEL_H
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#define KERNEL_H
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/* APIC is turned on by default */
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#define CONFIG_APIC
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/* boot verbose */
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#define CONFIG_BOOT_VERBOSE
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/*
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* compile in the nmi watchdog by default. It is not enabled until watchdog=1
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* (non-zero) is set in monitor
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*/
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#define CONFIG_WATCHDOG
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/* We only support 1 cpu now */
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#define CONFIG_MAX_CPUS 1
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#define cpuid 0
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/* measure cumulative idle timestamp counter ticks */
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#undef CONFIG_IDLE_TSC
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/* This is the master header for the kernel. It includes some other files
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* and defines the principal constants.
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*/
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#define _POSIX_SOURCE 1 /* tell headers to include POSIX stuff */
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#define _MINIX 1 /* tell headers to include MINIX stuff */
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#define _SYSTEM 1 /* tell headers that this is the kernel */
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/*
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* we need the defines above in assembly files to configure the kernel
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* correctly. However we don't need the rest
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*/
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#ifndef __ASSEMBLY__
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/* The following are so basic, all the *.c files get them automatically. */
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#include <minix/config.h> /* global configuration, MUST be first */
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#include <ansi.h> /* C style: ANSI or K&R, MUST be second */
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#include <sys/types.h> /* general system types */
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#include <minix/const.h> /* MINIX specific constants */
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#include <minix/type.h> /* MINIX specific types, e.g. message */
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#include <minix/ipc.h> /* MINIX run-time system */
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#include <minix/sysutil.h> /* MINIX utility library functions */
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#include <timers.h> /* watchdog timer management */
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#include <errno.h> /* return codes and error numbers */
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/* Important kernel header files. */
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#include "config.h" /* configuration, MUST be first */
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#include "const.h" /* constants, MUST be second */
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#include "type.h" /* type definitions, MUST be third */
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#include "proto.h" /* function prototypes */
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#include "glo.h" /* global variables */
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#include "ipc.h" /* IPC constants */
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#include "profile.h" /* system profiling */
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#include "debug.h" /* debugging, MUST be last kernel header */
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#endif /* __ASSEMBLY__ */
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#endif /* KERNEL_H */
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