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From: Martin Blapp <mb@imp.ch>
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Subject: GDB broken for some backtraces
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Hi all,

I wonder if this problem has already been adressed by someone:

http://lists.freebsd.org/pipermail/freebsd-arch/2005-July/004055.html

>It seems worse than that -- the gdb backtrace might show unknown or
>completely bogus frames as a result.  For example, we've run across
>the tty locking issue (discussed on -stable), and backtraces often
>look like:
>
>#6  0xa0723d8a in calltrap () at /usr/src/sys/i386/i386/exception.s:202
>#7  0xc7f10018 in ?? ()
>#8  0xa05b0010 in power_profile_set_state (state=0)
>    at /usr/src/sys/kern/subr_power.c:110
>#9  0xa05c942c in ttwakeup (tp=0xa23fdc00) at /usr/src/sys/kern/tty.c:2370
>#10 0xa05c7d71 in ttymodem (tp=0xa23fdc00, flag=0)
>    at /usr/src/sys/kern/tty.c:1625

A ddb trace is still readable then, but kgdb doesn't show a backtrace
and tells me it's hosed. All frames before frame 6 are corrupt in kgdb.

Any idea how to fix kgdb ?

Martin

Martin Blapp, <mb@imp.ch> <mbr@FreeBSD.org>
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