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Re: fg/bg on FreeBSD.



In article <1000506170828.ZM2063@xxxxxxxxxxxxxxxxxxxxxxx>,
  "Bart Schaefer" <schaefer@xxxxxxxxxxxxxxxxxxxxxxx> writes:

> Why is the PGID of sleep different on FreeBSD?  Did it change after the
> sleep was started because the echo exited?

Possibly.  But NetBSD has no problem...

| Z:akr@dhcp21% ktrace -i zsh -f              
| dhcp21% echo|sleep 10
| ^Z
| zsh: done       echo | 
| zsh: suspended  sleep 10
| dhcp21% jobs -l
| [1]  + 29257 done       echo | 
|        29258 suspended  sleep 10
| dhcp21% ps j29258
| USER   PID  PPID  PGID   SESS JOBC STAT  TT       TIME COMMAND
| akr  29258 29256 29258 94d480    1 T     p3    0:00.00 sleep 10
| dhcp21% bg
| [1]  + done       echo | 
|        continued  sleep 10
| dhcp21% ps j29258
| USER   PID  PPID  PGID   SESS JOBC STAT  TT       TIME COMMAND
| akr  29258 29256 29258 94d480    1 T     p3    0:00.00 sleep 10
| dhcp21% kill -9 29258
| [1]  + done       echo | 
|        killed     sleep 10
| dhcp21% exit
| Z:akr@dhcp21% kdump|egrep 'kill|fork|exit|setpgid'
|  29256 zsh      CALL  fork                    # zsh: fork for echo
|  29256 zsh      RET   fork 29257/0x7249
|  29257 zsh      RET   fork 0
|  29257 zsh      CALL  setpgid(0,0x7249)       # echo: setpgid(0,29257)
|  29257 zsh      RET   setpgid 0
|  29256 zsh      CALL  fork                    # zsh: fork for sleep
|  29256 zsh      RET   fork 29258/0x724a
|  29257 zsh      CALL  exit(0)                 # echo: exit(0)
|  29258 zsh      RET   fork 0
|  29258 zsh      CALL  kill(0xffff8db7,0)
|  29258 zsh      RET   kill -1 errno 3 No such process
|  29258 zsh      CALL  setpgid(0,0x724a)       # sleep: setpgid(0,29258)

Hm.  The process to be sleep command set its PGID itself.

|  29258 zsh      RET   setpgid 0
|  29256 zsh      CALL  kill(0xffff8db6,0)
|  29256 zsh      RET   kill 0
|  29256 zsh      CALL  fork                    # zsh: fork for ps
|  29256 zsh      RET   fork 29259/0x724b
|  29259 zsh      RET   fork 0
|  29259 zsh      CALL  setpgid(0,0x724b)
|  29259 zsh      RET   setpgid 0
|  29259 ps       CALL  exit(0)
|  29256 zsh      CALL  kill(0xfffe7960,0)
|  29256 zsh      RET   kill -1 errno 3 No such process
|  29256 zsh      CALL  kill(0xffff8db7,0x13)   # zsh: kill(-29257,SIGCONT)
|  29256 zsh      RET   kill -1 errno 3 No such process
|  29256 zsh      CALL  fork                    # zsh: fork for ps
|  29256 zsh      RET   fork 29260/0x724c
|  29260 zsh      RET   fork 0
|  29260 zsh      CALL  setpgid(0,0x724c)
|  29260 zsh      RET   setpgid 0
|  29260 ps       CALL  exit(0)
|  29256 zsh      CALL  kill(0xfffe7960,0)
|  29256 zsh      RET   kill -1 errno 3 No such process
|  29256 zsh      CALL  kill(0x724a,0x9)
|  29256 zsh      RET   kill 0
|                killed     sleep 10
|  29256 zsh      CALL  exit(0)
| Z:akr@dhcp21% 

> Please try the same test, but replace "echo" with "sleep 9" so that you
> can stop both jobs before either one of them exits.  Then see what the
> PGID of the second sleep is.

OK.

| Z:akr@dhcp21% ktrace -i zsh -f
| dhcp21% sleep 100|sleep 200
| ^Z
| zsh: suspended  sleep 100 | sleep 200

9 seconds are too short to check it...

| dhcp21% jobs -l
| [1]  + 29245 suspended  sleep 100 | 
|        29246 suspended  sleep 200
| dhcp21% ps j29245; ps j29246 
| USER   PID  PPID  PGID   SESS JOBC STAT  TT       TIME COMMAND
| akr  29245 29244 29245 94d480    2 T     p3    0:00.00 sleep 100
| USER   PID  PPID  PGID   SESS JOBC STAT  TT       TIME COMMAND
| akr  29246 29244 29245 94d480    2 T     p3    0:00.00 sleep 200

PGID is first sleep's PID.  It's good.

| dhcp21% bg
| [1]  + continued  sleep 100 | sleep 200
| dhcp21% ps j29245; ps j29246 
| USER   PID  PPID  PGID   SESS JOBC STAT  TT       TIME COMMAND
| akr  29245 29244 29245 94d480    2 I     p3    0:00.00 sleep 100
| USER   PID  PPID  PGID   SESS JOBC STAT  TT       TIME COMMAND
| akr  29246 29244 29245 94d480    2 I     p3    0:00.00 sleep 200

It's successfully resumed.

| dhcp21% kill %1
| [1]  + terminated  sleep 100 | sleep 200
| dhcp21% exit
| Z:akr@dhcp21% 

Note that this is the result of similar test on NetBSD.

| Z:akr@netbsd% ktrace -i zsh -f
| netbsd% echo|sleep 100
| ^Z
| zsh: done       echo | 
| zsh: suspended  sleep 100
| netbsd% jobs -l
| [1]  + 16520 done       echo | 
|        16521 suspended  sleep 100
| netbsd% ps j16521
| USER       PID  PPID  PGID   SESS JOBC STAT TT       TIME COMMAND
| akr      16521 16519 16520 c09fae40    1 T    p1    0:00.01 sleep 100 
| netbsd% bg
| [1]  + done       echo | 
|        continued  sleep 100
| netbsd% ps j16521
| USER       PID  PPID  PGID   SESS JOBC STAT TT       TIME COMMAND
| akr      16521 16519 16520 c09fae40    1 S    p1    0:00.01 sleep 100 
| netbsd% kill %1
| [1]  + done        echo | 
|        terminated  sleep 100
| netbsd% exit
| Z:akr@netbsd% kdump|egrep 'kill|fork|exit|setpgid'
|  16519 zsh      CALL  fork                    # zsh: fork for echo
|  16519 zsh      RET   fork 16520/0x4088
|  16520 zsh      RET   fork 0
|  16520 zsh      CALL  setpgid(0,0x4088)
|  16520 zsh      RET   setpgid 0
|  16520 zsh      CALL  exit(0)                 # echo: exit(0)
|  16519 zsh      CALL  fork                    # zsh: fork for sleep
|  16519 zsh      RET   fork 16521/0x4089
|  16521 zsh      RET   fork 0
|  16521 zsh      CALL  kill(0xffffbf78,0)
|  16521 zsh      RET   kill 0
|  16521 zsh      CALL  setpgid(0,0x4088)       # sleep: setpgid(0,16520)

It setpgid itself to 16520(echo's PID) correctly.

|  16521 zsh      RET   setpgid 0
|  16519 zsh      CALL  fork
|  16519 zsh      RET   fork 16522/0x408a
|  16522 zsh      RET   fork 0
|  16522 zsh      CALL  setpgid(0,0x408a)
|  16522 zsh      RET   setpgid 0
|  16519 zsh      CALL  kill(0xffff8acf,0)
|  16519 zsh      RET   kill -1 errno 3 No such process
|  16519 zsh      CALL  kill(0xffffbf78,0x13)
|  16519 zsh      RET   kill 0
|  16519 zsh      CALL  fork
|  16519 zsh      RET   fork 16523/0x408b
|  16523 zsh      RET   fork 0
|  16523 zsh      CALL  setpgid(0,0x408b)
|  16523 zsh      RET   setpgid 0
|  16519 zsh      CALL  kill(0xffff8acf,0)
|  16519 zsh      RET   kill -1 errno 3 No such process
|  16519 zsh      CALL  kill(0xffffbf78,0xf)
|  16519 zsh      RET   kill 0
|  16519 zsh      CALL  exit(0)
| Z:akr@netbsd% 
-- 
Tanaka Akira



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