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4.4 Finding a Panic String in a Thread Other Than the
Current Thread
The dbx and kdbx debuggers have the concept of the current thread. In
many cases, when you invoke one of the debuggers to analyze a crash
dump, the panic string is in the current thread. At times, however, the
current thread contains no panic string and so is probably not the thread
that caused the crash.
The following example shows a method for stepping through kernel threads
to identify the events that lead to the crash:
# dbx -k ./vmunix.2 ./vmzcore.2
dbx version 5.0
Type ’help’ for help.
thread 0x8d431c68 stopped at [thread_block:1305 +0x114,0xfffffc000033961c] \
Source not available
(dbx) p panicstr
1
0xfffffc000048a0c8 = "kernel memory fault"
(dbx) t
2
> 0 thread_block() ["../../../../src/kernel/kern/sched_prim.c":1305, 0xfffffc0\
e
00033961c]
1 mpsleep(chan = 0xffffffff8d4ef450 = , pri = 282, wmesg = 0xfffffc000046f\
290 = "network", timo = 0, lockp = (nil), flags = 0) ["../../../../src/kernel/\
bsd/kern_synch.c":267, 0xfffffc00002b772c]
2 sosleep(so = 0xffffffff8d4ef408, addr = 0xffffffff906cfcf4 = "^P", pri = 2 \
82,tmo = 0) ["../../../../src/kernel/bsd/uipc_socket2.c":612, 0xfffffc00002d3784]
3 accept1(p = 0xffffffff8f8bfde8, args = 0xffffffff906cfe50, retval = 0xffff \
ffff906cfe40, compat_43 = 1) ["../../../../src/kernel/bsd/uipc_syscalls.c":300 \
, 0xfffffc00002d4c74]
4 oaccept(p = 0xffffffff8d431c68, args = 0xffffffff906cfe50, retval = 0xffff \
ffff906cfe40) ["../../../../src/kernel/bsd/uipc_syscalls.c":250, 0xfffffc00002d\
4b0c]
5 syscall(ep = 0xffffffff906cfef8, code = 99, sr = 1) ["../../../../src/kern \
el/arch/alpha/syscall_trap.c":499, 0xfffffc00003ec18c]
6 _Xsyscall() ["../../../../src/kernel/arch/alpha/locore.s":675, 0xfffffc000\
03df96c]
(dbx) tlist
3
thread 0x8d431a60 stopped at [thread_block:1305 +0x114,0xfffffc000033961c] \
Source not available
thread 0x8d431858 stopped at [thread_block:1289 +0x18,0xfffffc00003394b8] \
Source not available
thread 0x8d431650 stopped at [thread_block:1289 +0x18,0xfffffc00003394b8] \
Source not available
thread 0x8d431448 stopped at [thread_block:1305 +0x114,0xfffffc000033961c] \
Source not available
thread 0x8d431240 stopped at [thread_block:1305 +0x114,0xfffffc000033961c] \
Source not available
.
.
.
thread 0x8d42f5d0 stopped at [boot:696 ,0xfffffc00003e119c] Source not
\
available
thread 0x8d42f3c8 stopped at [thread_block:1289 +0x18,0xfffffc00003394b8] \
Source not available
thread 0x8d42f1c0 stopped at [thread_block:1289 +0x18,0xfffffc00003394b8] \
Source not available
thread 0x8d42efb8 stopped at [thread_block:1289 +0x18,0xfffffc00003394b8] \
4–8 Crash Analysis Examples