[linuxkernelnewbies] Linux kernel: Triggering crash dumps on non-responsive systems using NMI

[Peter Teoh]

http://publib.boulder.ibm.com/infocenter/lnxinfo/v3r0m0/index.jsp?topic=/liaai/crashdump/liaaicrashdumptrignmi.htm ux on IBM systems > Configuring Remote Crash Dump on Linux Systems > Setting up additional conditions to trigger crash dumps Send feedback Triggering crash dumps on non-responsive systems using NMI The previous section describes how the Magic SysRq keys can be used to trigger a crash dump. However, they only work if the system still responds to console input. In failures where the system hangs and normal interrupts are disabled, you can use non maskable interrupts (NMIs) to trigger a panic and hence a crash dump. There are two ways to do it and they are incompatible. Only one of them can be enabled at a time: Using the NMI Watchdog to detect hangs This mechanism works on most hardware. When the NMI watchdog is enabled, the system hardware is programmed to periodically generate an NMI. Each NMI invokes a handler in the Linux kernel to check the count of certain interrupts. If the handler detects that this count has not increased over a certain period of time, it assumes the system is hung. It then invokes the panic routine. If Kdump is enabled, the routine also saves a crash dump. Generating a NMI manually when hang An alternative to the NMI watchdog is to generate a NMI manually. This section describes how to configure the Linux kernel to call the panic routine when it receives an NMI with an unknown code. In many cases it is possible to generate such an NMI on a hung system to cause a panic and hence a crash dump. Parent topic: Setting up additional conditions to trigger crash dumps