panic: stable/10 with Debugging enabled in kern_cons.c:500

[Sean Bruno]

On Sat, 2014-01-11 at 14:12 -0800, Sean Bruno wrote:
> I can't imagine that I'm the first person to run with the following
> debug options enabled:
> 
> http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug-deadlocks.html
> 
> But, I can't get stable/10 to post on a plain old supermicro box with
> those debugging symbols enabled.  
> 
> 
> random: unblocking device.
> panic: mtx_lock_spin: recursed on non-recursive mutex cnputs_mtx
> @ /usr/src/sys/kern/kern_cons.c:500
> 
> cpuid = 0
> KDB: stack backtrace:
> db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame
> 0xfffffe1764e681b0
> kdb_backtrace() at kdb_backtrace+0x39/frame 0xfffffe1764e68260
> vpanic() at vpanic+0x126/frame 0xfffffe1764e682a0
> kassert_panic() at kassert_panic+0x136/frame 0xfffffe1764e68310
> __mtx_lock_spin_flags() at __mtx_lock_spin_flags+0x166/frame
> 0xfffffe1764e68350
> cnputs() at cnputs+0x32/frame 0xfffffe1764e68370
> putchar() at putchar+0x13a/frame 0xfffffe1764e683f0
> kvprintf() at kvprintf+0xda/frame 0xfffffe1764e684f0
> vprintf() at vprintf+0x87/frame 0xfffffe1764e685c0
> printf() at printf+0x43/frame 0xfffffe1764e68620
> witness_checkorder() at witness_checkorder+0xa99/frame
> 0xfffffe1764e686b0
> __mtx_lock_spin_flags() at __mtx_lock_spin_flags+0x95/frame
> 0xfffffe1764e686f0
> uart_cnputc() at uart_cnputc+0x3b/frame 0xfffffe1764e68710
> cnputc() at cnputc+0x7f/frame 0xfffffe1764e68740
> cnputs() at cnputs+0x58/frame 0xfffffe1764e68760
> putchar() at putchar+0x13a/frame 0xfffffe1764e687e0
> kvprintf() at kvprintf+0xda/frame 0xfffffe1764e688e0
> vprintf() at vprintf+0x87/frame 0xfffffe1764e689b0
> printf() at printf+0x43/frame 0xfffffe1764e68a10
> witness_checkorder() at witness_checkorder+0xa99/frame
> 0xfffffe1764e68aa0
> __mtx_lock_spin_flags() at __mtx_lock_spin_flags+0x95/frame
> 0xfffffe1764e68ae0
> msleep_spin_sbt() at msleep_spin_sbt+0x90/frame 0xfffffe1764e68b70
> random_kthread() at random_kthread+0x1d0/frame 0xfffffe1764e68bb0
> fork_exit() at fork_exit+0x84/frame 0xfffffe1764e68bf0
> fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe1764e68bf0
> --- trap 0, rip = 0, rsp = 0xfffffe1764e68cb0, rbp = 0 ---
> KDB: enter: panic
> [ thread pid 14 tid 100057 ]
> Stopped at      kdb_enter+0x3e: movq    $0,kdb_why


Witness induced.  Removed the witness option and this doesn't happen
(obviously).  Can I get someone familiar with console code to look into
this?  Kind of crappy when I'm investigating a resource starvation
issue.

sean