I have several core dumps that need debugged. All are the same problem.
The debugging problem is when I fire up kgdb, I have to backtrace even
though the kernel message buffer contains a back trace. If I try to set
the frame with "frame 0xffffff8020bddb30" I get an error "Cannot access
memory at address 0x0". All I have to debug with are these two pieces
of information. How do I get more information?
jri.homeunix.com dumped core - see /var/crash/vmcore.29
Sun Mar 24 10:49:52 CDT 2013
FreeBSD jri.homeunix.com 10.0-CURRENT FreeBSD 10.0-CURRENT #0 r248680M: Sun Mar
24 07:13:16 CDT 2013 r
panic: kdb_switch: did not reenter debugger
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This GDB was configured as "amd64-marcel-freebsd"...
Unread portion of the kernel message buffer:
witness_warn() at witness_warn+0x4a8/frame 0xffffff8020bdd690
trap_pfault() at trap_pfault+0x5a/frame 0xffffff8020bdd740
trap() at trap+0x659/frame 0xffffff8020bdd950
calltrap() at calltrap+0x8/frame 0xffffff8020bdd950
--- trap 0xc, rip = 0xffffffff8133519e, rsp = 0xffffff8020bdda10, rbp =
0xffffff8020bddb30 ---
ath_edma_tx_processq() at ath_edma_tx_processq+0x18e/frame 0xffffff8020bddb30
taskqueue_run_locked() at taskqueue_run_locked+0xf0/frame 0xffffff8020bddb80
taskqueue_thread_loop() at taskqueue_thread_loop+0x9b/frame 0xffffff8020bddbb0
fork_exit() at fork_exit+0x84/frame 0xffffff8020bddbf0
fork_trampoline() at fork_trampoline+0xe/frame 0xffffff8020bddbf0
--- trap 0, rip = 0, rsp = 0xffffff8020bddcb0, rbp = 0 ---
Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address = 0x0
fault code = supervisor read data, page not present
instruction pointer = 0x20:0xffffffff8133519e
stack pointer = 0x28:0xffffff8020bdda10
frame pointer = 0x28:0xffffff8020bddb30
code segment = base 0x0, limit 0xfffff, type 0x1b
= DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags = interrupt enabled, resume, IOPL = 0
current process = 0 (ath0 taskq)
Uptime: 2m19s
Dumping 261 out of 1771 MB:..7%..13%..25%..31%..43%..56%..62%..74%..86%..92%
(kgdb) list *(0xffffffff8133519e)
0xffffffff8133519e is in ath_edma_tx_processq
(/root/ATH/head/sys/modules/ath/../../dev/ath/if_ath_tx_edma.c:552).
547 bf->bf_descid);
548 }
549 #endif
550
551 /* This removes the buffer and decrements the queue
depth */
552 ATH_TXQ_REMOVE(txq, bf, bf_list);
553 if (bf->bf_state.bfs_aggr)
554 txq->axq_aggr_depth--;
555 txq->axq_fifo_depth --;
556 /* XXX assert FIFO depth >= 0 */
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