[20190401]跟蹤dbms_lock.sleep調用.txt

--//自己在semtimedop函數調用理解錯誤,加深理解,跟蹤dbms_lock.sleep調用的情況.

1.環境:
SCOTT@book> @ ver1
PORT_STRING??????????????????? VERSION??????? BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx??????????? 11.2.0.4.0???? Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

grant EXECUTE ON? dbms_lock to scott;

SCOTT@book> @ spid
?????? SID??? SERIAL# PROCESS????????????????? SERVER??? SPID?????? PID? P_SERIAL# C50
---------- ---------- ------------------------ --------- ------ ------- ---------- --------------------------------------------------
??????? 51????????? 7 60257??????????????????? DEDICATED 60258?????? 27??????? 123 alter system kill session '51,7' immediate;

?$ strace -fTr -e semtimedop -p 60258
Process 60258 attached - interrupt to quit

--//僅僅跟蹤semtimedop.

2.測試:
SCOTT@book> exec dbms_lock.sleep(5.3)
PL/SQL procedure successfully completed.

$ strace -fTr -e semtimedop -p 60258
Process 60258 attached - interrupt to quit
???? 0.000000 semtimedop(309821440, 0x7fffe52f9ac0, 1, {5, 300000000}) = -1 EAGAIN (Resource temporarily unavailable) <5.300886>
--//可以發現實際上執行dbms_lock.sleep(5.3),調用函數是semtimedop,睡眠5.3秒.

SCOTT@book> exec dbms_lock.sleep(10.3)
PL/SQL procedure successfully completed.

$ strace -fTr -e semtimedop -p 60258
..
??? 65.217301 semtimedop(309821440, 0x7fffe52f9ac0, 1, {3, 0}) = -1 EAGAIN (Resource temporarily unavailable) <3.000460>
???? 3.000610 semtimedop(309821440, 0x7fffe52f9ac0, 1, {3, 0}) = -1 EAGAIN (Resource temporarily unavailable) <3.000960>
???? 3.001073 semtimedop(309821440, 0x7fffe52f9ac0, 1, {4, 300000000}) = -1 EAGAIN (Resource temporarily unavailable) <4.300934>

--//你可以基本看出執行dbms_lock.sleep大致算法,oracle許多東西都與3秒有關.
--//分成多個3秒,開始調用semtimedop 3秒,剩下部分小于2*3秒時,調用剩余的部分.

--//再次測試,在執行的過程中打開新終端窗口,執行kill -1 60258.
SCOTT@book> exec dbms_lock.sleep(10.3)
--//中間執行:
$ kill -1 60258

PL/SQL procedure successfully completed.

--//注:kill -1 并不會殺死進程,僅僅掛起.可以通過kill -l了解一些細節.
?$ kill -l
?1) SIGHUP?????? 2) SIGINT?????? 3) SIGQUIT????? 4) SIGILL
?5) SIGTRAP????? 6) SIGABRT????? 7) SIGBUS?????? 8) SIGFPE
?9) SIGKILL???? 10) SIGUSR1???? 11) SIGSEGV???? 12) SIGUSR2
13) SIGPIPE???? 14) SIGALRM???? 15) SIGTERM???? 16) SIGSTKFLT
17) SIGCHLD???? 18) SIGCONT???? 19) SIGSTOP???? 20) SIGTSTP
21) SIGTTIN???? 22) SIGTTOU???? 23) SIGURG????? 24) SIGXCPU
25) SIGXFSZ???? 26) SIGVTALRM?? 27) SIGPROF???? 28) SIGWINCH
29) SIGIO?????? 30) SIGPWR????? 31) SIGSYS????? 34) SIGRTMIN
35) SIGRTMIN+1? 36) SIGRTMIN+2? 37) SIGRTMIN+3? 38) SIGRTMIN+4
39) SIGRTMIN+5? 40) SIGRTMIN+6? 41) SIGRTMIN+7? 42) SIGRTMIN+8
43) SIGRTMIN+9? 44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12
47) SIGRTMIN+13 48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14
51) SIGRTMAX-13 52) SIGRTMAX-12 53) SIGRTMAX-11 54) SIGRTMAX-10
55) SIGRTMAX-9? 56) SIGRTMAX-8? 57) SIGRTMAX-7? 58) SIGRTMAX-6
59) SIGRTMAX-5? 60) SIGRTMAX-4? 61) SIGRTMAX-3? 62) SIGRTMAX-2
63) SIGRTMAX-1? 64) SIGRTMAX

$ strace -fTr -e semtimedop -p 60258
..
?? 154.662451 semtimedop(309821440, 0x7fffe52f9ac0, 1, {3, 0}) = -1 EAGAIN (Resource temporarily unavailable) <3.000463>
???? 3.000651 semtimedop(309821440, 0x7fffe52f9ac0, 1, {3, 0}) = -1 EINTR (Interrupted system call) <1.573761>
???? 1.573876 --- SIGHUP (Hangup) @ 0 (0) ---
???? 0.000203 semtimedop(309821440, 0x7fffe52f9ac0, 1, {5, 730000000}) = -1 EAGAIN (Resource temporarily unavailable) <5.730875>
--//在第2個3秒中發出了中斷,僅僅執行1.57秒.最后1次調用執行 4.3+1.43 = 5.73秒.

--//再次測試,中間按ctrl+c看看:
SCOTT@book> exec dbms_lock.sleep(10.3)
BEGIN dbms_lock.sleep(10.3); END;

*
ERROR at line 1:
ORA-01013: user requested cancel of current operation
ORA-06512: at "SYS.DBMS_LOCK", line 205
ORA-06512: at line 1

$ strace -fTr -e semtimedop -p 60258
..
??? 14.543729 semtimedop(309821440, 0x7fffe52f9ac0, 1, {3, 0}) = -1 EINTR (Interrupted system call) <2.880053>
???? 2.880177 --- SIGURG (Urgent I/O condition) @ 0 (0) ---
--//中斷不再繼續執行.

--//再次測試,中間執行kill -19 60258, 19表示SIGSTOP,暫停執行.
$ strace -fTr -e semtimedop -p 60258
..

?? 172.564623 semtimedop(309821440, 0x7fffe52f9ac0, 1, {3, 0}) = -1 EINTR (Interrupted system call) <2.343982>
???? 2.344113 --- SIGSTOP (Stopped (signal)) @ 0 (0) ---
???? 0.000071 --- SIGSTOP (Stopped (signal)) @ 0 (0) ---
???? 0.000326 semtimedop(309821440, 0x7fffe52f9ac0, 1, {3, 0}) = -1 EAGAIN (Resource temporarily unavailable) <3.000768>
???? 3.000904 semtimedop(309821440, 0x7fffe52f9ac0, 1, {4, 960000000}) = -1 EAGAIN (Resource temporarily unavailable) <4.960862>

--//可以發現僅僅暫停第1個3秒的執行.總的sleep時間是不變的.
--//2.343982+3.000768+4.960862 = 10.305612
--//后續的sql語句并不影響執行.

--//做這些測試僅僅是加強理解..^_^.

--//順便說一下linux sleep調用的是nanosleep.
$ strace sleep 10.3
...
brk(0x1d63000)????????????????????????? = 0x1d63000
nanosleep({10, 300000001}, NULL)??????? = 0
close(1)??????????????????????????????? = 0
exit_group(0)?????????????????????????? = ?

轉載于:https://www.cnblogs.com/lfree/p/10637471.html

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