Date: Tue, 28 Nov 2000 16:54:07 -0400 (AST) From: The Hermit Hacker <scrappy@hub.org> To: John Baldwin <jhb@FreeBSD.org> Cc: freebsd-current@FreeBSD.org Subject: RE: -current kernel hangs machine solid ... Message-ID: <Pine.BSF.4.21.0011281653240.323-100000@thelab.hub.org> In-Reply-To: <XFMail.001128124310.jhb@FreeBSD.org>
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gah ... okay, first "problem" is coming up with a serial console, as I only have the one machine ... but, am going to search one out and save this email ... will come back to it once I get it setup that far ... thanks ... On Tue, 28 Nov 2000, John Baldwin wrote: > > On 28-Nov-00 The Hermit Hacker wrote: > > > > Just tried to build a kernel based on sources from today, to enable > > BREAK_TO_DEBUGGER so that I can try and get in and see where its hanging > > ... the compile hung the machine solid. Even hitting the > > 'numlock'/'capslock' on my keyboard generated no results ... > > It is spinning with interrupts disabled, probably due to holding a spinlock for > far too long. Debugging this is not all that fun. :-P If you can rig up an > NMI switch, you can use that to drop into ddb and then use 'x' to see who owns > various mutexes (sched_lock and callout_mtx being the primary spin mutexes of > concern). If you compile your kernel with WITNESS and MUTEX_DEBUG, then you > can use 'x' to look at the sched_lock and callout_mtx mutex structures, find > the pointer to the mtx_debug structure, and examine that to find the mtxd_file > and mtxd_line members. Then you can look at those (x/s to look at the filename > as a string) to find the filename and line number when the mutex was last > acquired. Grr, except that this is broken for spin mutexes. If you are > patient, you can try rigging up a serial console, compile KTR into your kernel > as so: > > options KTR > options KTR_EXTEND > options KTR_COMPILE=(KTR_LOCK|KTR_PROC|KTR_INTR) > > Then when the machine has booted, log in via ssh or a tty other than the serial > console and type the following: > > # sysctl -w debug.ktr_mask=0x1208 > # sysctl -w debug.ktr_verbose=2 > # while (1) do > > make -j 16 buildworld > > end > > Unfortunately, there is a chance the machine will die before it hangs due to > exceeding the stack space. In that case, you can _try_ bumping UPAGES, but > that didn't help on my test machines. :-/ However, if your machine doesn't > blow up and die, then when it hangs, the KTR output dumped to the serial console > (which you should probably log to a file via script or somesuch) will show what > mutex was acquired and where it was acquired that is causing the hang. > > -- > > John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/ > PGP Key: http://www.baldwin.cx/~john/pgpkey.asc > "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ > Marc G. Fournier ICQ#7615664 IRC Nick: Scrappy Systems Administrator @ hub.org primary: scrappy@hub.org secondary: scrappy@{freebsd|postgresql}.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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