On Tue, 2009-11-17 at 16:28 -0800, Eric W. Biederman wrote: > David VomLehn <dvomlehn@xxxxxxxxx> writes: > > > On Tue, Nov 17, 2009 at 10:45:43AM -0500, Eric W. Biederman wrote: > > ... > >> Why not use the kdump hook? If you handle a kernel panic that way > >> you get enhanced reliability and full user space support. All in a hook > >> that is already present and already works. > > > > I'm a big fan of avoiding reinvention of the wheel--if I can use something > > already present, I will. However, I'm not clear about how much of the problem > > I'm addressing will be solved by using a kdump hook. If I understand > > correctly, you'd still need a pseudo-file somewhere to actually get the data > > from user space to kernel space. *Then* you could use a kdump hook to > > transfer the data to flash or some memory area that will be retained across > > boots. Is this the approach to which you were referring? If so, I have a > > couple more questions: > > > > 1. In what ways would this be better than, say, a panic_notifier? > > A couple of ways. > > - You are doing the work in a known good kernel instead of the kernel > that just paniced for some unknown reason. > - All of the control logic is in user space (not the kernel) so you can > potentially do something as simple as "date >> logfile" to get the > date. > > > 2. Where would you suggest tying in? (Particularly since not all architectures > > currently support kdump) > > No changes are needed kernel side. You just need an appropriate kernel and > initrd for your purpose. > > All of the interesting architectures support kexec, and if an > architecture doesn't it isn't hard to add. The architecture specific > part is very simple. A pain to debug initially but very simple. As much as I like kexec, it loses on memory footprint by about 100x. It's not appropriate for all use cases, especially things like consumer-grade wireless access points and phones. -- http://selenic.com : development and support for Mercurial and Linux -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
