At 10/21/2011 03:11 PM, Jan Kiszka Write: > On 2011-10-20 12:03, Wen Congyang wrote: >> At 10/20/2011 05:41 PM, Jan Kiszka Write: >>> On 2011-10-20 03:22, Wen Congyang wrote: >>>>>> I didn't read full story but 'crash' is used for investigating kernel >>>>>> core generated >>>>>> by kdump for several years. Considering support service guys, virsh dump >>>>>> should support >>>>>> a format for crash because they can't work well at investigating vmcore >>>>>> by gdb. >>>>>> >>>>>> crash has several functionality useful for them as 'show kerne log', >>>>>> 'focus on a cpu' >>>>>> 'for-each-task', 'for-each-vma', 'extract ftrace log' etc. >>>>>> >>>>>> Anyway, if a man, who is not developper of qemu/kvm, should learn 2 >>>>>> tools for >>>>>> investigating kernel dump, it sounds harmful. >>>>> >>>>> Right, that's why everything (live debugging & crash analysis) should be >>>>> consolidated on the long run over gdb. crash is architecturally obsolete >>>>> today - not saying it is useless! >>>> >>>> I do not know why crash is obsoleted today. Is there a new better tool to >>>> instead >>>> crash? >>> >>> I'm not aware of equally powerful (python) scripts for gdb as >>> replacement, but I think it's worth starting a porting effort at some point. >>> >>>> >>>> At least, I always use crash to live debugging & crash analysis. >>> >>> Then you may answer some questions to me: >>> - Can you attach to a remote target (kgdb, qemu, etc.) and how? >> >> No. crash's live debugging only can work the kernel is live. I can use it get >> some var's value, or some other information from kernel. If kernel panics, >> we can use gdb to attach to a remote target as you said. But on end user >> machine, >> we can not do it, we should dump the memory into a file and analyze it in >> another >> machine while the end user's guest can be restart. >> >>> - Can you use it with latest gdb versions or is the gdb functionality >>> hard-wired due to an embedded gdb core in crash (that's how I >>> understood Christoph's reply to this topic) >> >> If I use crash, I can not use latest gdb versions. Do we always need to use >> the latest gdb versions? Currently, gdb-7.0 is embedded into crash, and it >> is enough to me. If the gdb embedded into crash cannot anaylze the vmcore, I >> think we can update it and rebuild crash. > > crash is simply designed the wrong way around (from today's > perspective): it should augment upstream gdb instead of forking it.
Cc Dave Anderson. He knows how crash uses gdb. I think that crash does not fork a task to execute gdb, and gdb is a part of crash. Thanks Wen Congyang > > Jan >
