gdb調試之---當update時第一個持有的Latch是什麼Latch鎖？

1、查出目前會話所對應的系統程序号：SPID=7376，如下語句（在第一個視窗執行）

gyj@OCM> select spid from v$session s,v$process p where s.paddr=p.addr and sid in(select distinct sid from v$mystat);

SPID
------------------------
7376           

2、 通過系統程序号7376打開gdb程式（在第二個視窗執行）

[oracle@mydb ~]$ gdb $ORACLE_HOME/bin/oracle 7376
GNU gdb Fedora (6.8-27.el5)
Copyright (C) 2008 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu"...
(no debugging symbols found)
Attaching to program: /u01/app/oracle/product/11.2.0/bin/oracle, process 7376
Reading symbols from /u01/app/oracle/product/11.2.0/lib/libodm11.so...(no debugging symbols found)...done.
Loaded symbols for /u01/app/oracle/product/11.2.0/lib/libodm11.so
Reading symbols from /u01/app/oracle/product/11.2.0/lib/libcell11.so...done.
Loaded symbols for /u01/app/oracle/product/11.2.0/lib/libcell11.so
Reading symbols from /u01/app/oracle/product/11.2.0/lib/libskgxp11.so...done.
Loaded symbols for /u01/app/oracle/product/11.2.0/lib/libskgxp11.so
Reading symbols from /lib64/librt.so.1...done.
Loaded symbols for /lib64/librt.so.1
Reading symbols from /u01/app/oracle/product/11.2.0/lib/libnnz11.so...done.
Loaded symbols for /u01/app/oracle/product/11.2.0/lib/libnnz11.so
Reading symbols from /u01/app/oracle/product/11.2.0/lib/libclsra11.so...done.
Loaded symbols for /u01/app/oracle/product/11.2.0/lib/libclsra11.so
Reading symbols from /u01/app/oracle/product/11.2.0/lib/libdbcfg11.so...done.
Loaded symbols for /u01/app/oracle/product/11.2.0/lib/libdbcfg11.so
Reading symbols from /u01/app/oracle/product/11.2.0/lib/libhasgen11.so...done.
Loaded symbols for /u01/app/oracle/product/11.2.0/lib/libhasgen11.so
Reading symbols from /u01/app/oracle/product/11.2.0/lib/libskgxn2.so...done.
Loaded symbols for /u01/app/oracle/product/11.2.0/lib/libskgxn2.so
Reading symbols from /u01/app/oracle/product/11.2.0/lib/libocr11.so...done.
Loaded symbols for /u01/app/oracle/product/11.2.0/lib/libocr11.so
Reading symbols from /u01/app/oracle/product/11.2.0/lib/libocrb11.so...done.
Loaded symbols for /u01/app/oracle/product/11.2.0/lib/libocrb11.so
Reading symbols from /u01/app/oracle/product/11.2.0/lib/libocrutl11.so...done.
Loaded symbols for /u01/app/oracle/product/11.2.0/lib/libocrutl11.so
Reading symbols from /usr/lib64/libaio.so.1...done.
Loaded symbols for /usr/lib64/libaio.so.1
Reading symbols from /lib64/libdl.so.2...done.
Loaded symbols for /lib64/libdl.so.2
Reading symbols from /lib64/libm.so.6...done.
Loaded symbols for /lib64/libm.so.6
Reading symbols from /lib64/libpthread.so.0...done.
[Thread debugging using libthread_db enabled]
[New Thread 0x2b0b8fef0910 (LWP 7376)]
Loaded symbols for /lib64/libpthread.so.0
Reading symbols from /lib64/libnsl.so.1...done.
Loaded symbols for /lib64/libnsl.so.1
Reading symbols from /lib64/libc.so.6...done.
Loaded symbols for /lib64/libc.so.6
Reading symbols from /lib64/ld-linux-x86-64.so.2...done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
Reading symbols from /usr/lib64/libnuma.so.1...done.
Loaded symbols for /usr/lib64/libnuma.so.1
Reading symbols from /lib64/libnss_files.so.2...done.
Loaded symbols for /lib64/libnss_files.so.2
Reading symbols from /u01/app/oracle/product/11.2.0/lib/libnque11.so...done.
Loaded symbols for /u01/app/oracle/product/11.2.0/lib/libnque11.so
0x0000003f0d40d290 in __read_nocancel () from /lib64/libpthread.so.0
(gdb)           

3、設一個斷點，持有第一個Latch鎖(預先知道函數kslgetl就是持有Latch的函數)，并運作（c指令，即

`

js

(gdb) b kslgetl

Breakpoint 1 at 0x8f96376

(gdb) c

Continuing.

4、執行一個update語句，觸發斷點的操作，此時update被阻塞了（在第一個視窗執行）           

gyj@OCM> update gyj_test set name='AAAAA' where id=1;

5、一執行updater操作，斷點就停在這兒了（在第二個視窗執行）           

Breakpoint 1, 0x0000000008f96376 in kslgetl ()

(gdb)

6、我們先來看update時持有第一個Latch鎖所對應函數kslgetl ()的第一個參數是什麼？用指令info all-register顯示寄存器（在第二個視窗執行）           

(gdb) info all-register

rax 0x0 0

rbx 0x2000 8192

rcx 0xf27 3879

rdx 0x0 0

rsi 0x1 1

rdi 0x601082f0 1611694832

rbp 0x7fff1c5754d0 0x7fff1c5754d0

rsp 0x7fff1c5754d0 0x7fff1c5754d0

r8 0xf27 3879

r9 0xbaf3fa0 196034464

r10 0x0 0

r11 0xf27 3879

r12 0x927db800 2457712640

r13 0x601082f0 1611694832

r14 0x1 1

r15 0x1 1

rip 0x8f96376 0x8f96376 <kslgetl+4>

eflags 0x246 [ PF ZF IF ]

cs 0x33 51

ss 0x2b 43

ds 0x0 0

es 0x0 0

fs 0x0 0

gs 0x0 0

st0 0 (raw 0x00000000000000000000)

---Type to continue, or q to quit---

st1 0 (raw 0x00000000000000000000)

st2 0 (raw 0x00000000000000000000)

st3 0 (raw 0x00000000000000000000)

st4 0 (raw 0x00000000000000000000)

st5 0 (raw 0x00000000000000000000)

st6 333296 (raw 0x4011a2be000000000000)

st7 300384 (raw 0x401192ac000000000000)

fctrl 0x27f 639

fstat 0x0 0

ftag 0xffff 65535

fiseg 0x0 0

fioff 0x9394e95 154750613

foseg 0x7fff 32767

fooff 0x1c573f50 475479888

fop 0x0 0

xmm0 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x0 }, v8_int16 = {0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0}, uint128 = 0x00000000000000000000000000000000}           

xmm1 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x0 }, v8_int16 = {0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0}, uint128 = 0x00000000000000000000000000000000}           

xmm2 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x0 }, v8_int16 = {0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0}, uint128 = 0x00000000000000000000000000000000}           

xmm3 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x8000000000000000, 0x8000000000000000}, v16_int8 = {0xfe, 0xff, 0xff, 0xff,

0xff, 0xff, 0xff, 0xff, 0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}, v8_int16 = {0xfffe, 0xffff, 0xffff, 0xffff, 0xfffe, 0xffff,
0xffff, 0xffff}, v4_int32 = {0xfffffffe, 0xffffffff, 0xfffffffe, 0xffffffff}, v2_int64 = {0xfffffffffffffffe, 0xfffffffffffffffe},           

uint128 = 0xfffffffffffffffefffffffffffffffe}

xmm4 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x0 }, v8_int16 = {0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0}, uint128 = 0x00000000000000000000000000000000}           

xmm5 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x32, 0xa3, 0xd7, 0x2, 0x0 },

v8_int16 = {0xa332, 0x2d7, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x2d7a332, 0x0, 0x0, 0x0}, v2_int64 = {0x2d7a332, 0x0},

uint128 = 0x00000000000000000000000002d7a332}

xmm6 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x0 }, v8_int16 = {0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0}, uint128 = 0x00000000000000000000000000000000}           

xmm7 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0xda, 0x87, 0xd7, 0x2, 0x0 },

v8_int16 = {0x87da, 0x2d7, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x2d787da, 0x0, 0x0, 0x0}, v2_int64 = {0x2d787da, 0x0},

uint128 = 0x00000000000000000000000002d787da}

xmm8 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x0 }, v8_int16 = {0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0}, uint128 = 0x00000000000000000000000000000000}           

xmm9 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x0 }, v8_int16 = {0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0}, uint128 = 0x00000000000000000000000000000000}           

xmm10 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x0 }, v8_int16 = {0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0}, uint128 = 0x00000000000000000000000000000000}           

xmm11 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x0 }, v8_int16 = {0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0}, uint128 = 0x00000000000000000000000000000000}           

xmm12 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x18, 0xe, 0x73, 0x90, 0xb, 0x2b, 0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0, 0x0, 0x0}, v8_int16 = {0xe18, 0x9073, 0x2b0b, 0x0, 0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x90730e18, 0x2b0b, 0x0, 0x0},           

v2_int64 = {0x2b0b90730e18, 0x0}, uint128 = 0x000000000000000000002b0b90730e18}

xmm13 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x0 }, v8_int16 = {0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0}, uint128 = 0x00000000000000000000000000000000}           

xmm14 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x0 }, v8_int16 = {0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0}, uint128 = 0x00000000000000000000000000000000}           

xmm15 {v4_float = {0x0, 0x0, 0x0, 0x0}, v2_double = {0x0, 0x0}, v16_int8 = {0x0 }, v8_int16 = {0x0, 0x0, 0x0, 0x0,

0x0, 0x0, 0x0, 0x0}, v4_int32 = {0x0, 0x0, 0x0, 0x0}, v2_int64 = {0x0, 0x0}, uint128 = 0x00000000000000000000000000000000}           

mxcsr 0x1fa1 [ IE PE IM DM ZM OM UM PM ]

7、rdi/edi是第一個參數， rsi/esi是第二個參數，貼出info all-register指令所顯示函數kslgetl ()的兩個參數，如下
rsi            0x1      1                   ----第二個參數
rdi            0x601082f0       1611694832  ----第一個參數

8、找到第一個參數0x601082f0,注意因我的OS是64位，前面要補8個0，在v$latch_children視圖中位址的字母要大寫,
即0x601082f0要寫為00000000601082F0

9、通過視圖v$latch_children找Latch鎖（在第三個視窗執行）           

sys@OCM> select name from v$latch_children where addr='00000000601082F0';

NAME

shared pool