Hi Vivek, (2014/04/15 4:31), Vivek Goyal wrote: > On Mon, Apr 14, 2014 at 01:51:58PM +0900, Masami Hiramatsu wrote: >> Add a "late_kdump" option to run kdump after running panic >> notifiers and dump kmsg. This can help rare situations which >> kdump drops in failure because of unstable crashed kernel >> or hardware failure (memory corruption on critical data/code), >> or the 2nd kernel is broken by the 1st kernel (it's a broken >> behavior, but who can guarantee that the "crashed" kernel >> works correctly?). >> >> Usage: add "late_kdump" to kernel boot option. That's all. >> >> Note that this actually increases risks of the failure of >> kdump. This option should be set only if you worry about >> the rare case of kdump failure rather than increasing the >> chance of success. >> > > Masami, > > So what's the alternative to kdump which is more reliable? IOW, what > action you are planning to take through kmsg_dump() or through > panic_notifiers? > > I have seen that many a times developers have tried to make the case > to save kernel buffers to NVRAM. Does it work well? Has it been proven > to be more reliable than kdump?
Yeah, one possible option is the NVRAM, but even with the serial, there are other reasons to kick the notifiers, e.g. - dump to ipmi which has a very small amount of non-volatile memory - ftrace_dump() to dump "flight recorder" log to serial - pvpanic notifies panic to the host. Anyway, I think the most important reason for linux developers is that we have a chance to improve such horrible notifiers to safer, or at least to clarify what notifier or behavior makes kdump unstable. :-) Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
