Date: Wed, 6 Oct 2004 16:24:38 -0700 (PDT) From: Don Lewis <truckman@FreeBSD.org> To: rik@cronyx.ru Cc: hackers@FreeBSD.org Subject: Re: Printing from kernel Message-ID: <200410062324.i96NOc4b056930@gw.catspoiler.org> In-Reply-To: <41645625.3020209@cronyx.ru>
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On 7 Oct, Roman Kurakin wrote: > Hi, > > I have some problems with printing from kernel. > At first I think that my problems was cause I use printf, > but changed all of them to log cause it safe to use from > interrupt handlers. The situation become better but I still > observe system lockup in case I output some debug information > from my driver. > > Also I have some problems with system console via com > port. Instead of messages from kernel I see the first letter > of the month name. This is a bug in syslogd related to non-blocking I/O that bde and I discussed quite a while back, though we never figured out a proper fix. I recently made the interesting discovery that the same problem isn't present on sparc64. I think it'll start working again if you restart syslogd. > Could anybody comment my observation? Does anybody > saw anything like this? > > Oh, I forget to say I observe that with both Current > and Releng5, SMP. Also I can't trigger NMI so I can't see the > point of lockup. I generally use printf for this sort of thing, and I was going to suggest that you take a look at the KTR stuff, but that won't help if the machine totally locks up so that you can't get to the KTR buffer. I think you'll have trouble getting close to the bug if you use log because of the log latency from the generation of the message, passing it through syslogd, and back to the kernel to be printed.
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