On Tue, May 02, 2006 at 07:12:31AM +0200, Andi Kleen wrote: > > > > Ok if the goal is to force the subsystems to rely on die notifier chain > > instead of nmi_callback and getting rid of set_nmi_callback() interfaces, > > then it spells some problems for kdump, as kdump is different for other > > subsystems. You rightly pointed out that what if chain is corrupted > > or if some die notifier funciton hangs. > > All NMI handlers think they are different and more special than everybody > else. Otherwise they wouldn't be NMI. kdump is really in no way special. > > > > > Looks like that notifiers are called in increasing priority order. Looking > > at the code, it looks like notifier with priority 0x7fffffff will be called > > first. But still there is no gurantee. People registering first with > > this priority will be called first. Kdump registers in then end hence > > will be called last, so liable to fail. > > Sorry, but that's just a dumb argument. All kernel code needs to cooperate > with others - if there is a problem it's just fixed. But having multiple > callbacks just because you don't trust someone else doesn't make sense. >
I agree that normally all the parts of subsystem are supposed to co-operate and if there are bugs they need to be fixed. Proabably above apporach works most of the time. Its all about that small possibility when die chain is corrupted or there is a bug in registered notifier handler which went unnoticed. I am not advocating multiple callbacks. Probably once we have decided that system has crashed and we need to reboot into capture kernel, then we can replace the NMI interrupt handler altogether (at IDT level). Thanks Vivek
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