Re: Process generating its own stack trace

On May 17, 5:48 pm, Paul Pluzhnikov <ppluzhnikov-...@xxxxxxxxx> wrote:
Wind <umesh_wagh...@xxxxxxxxx> writes:
My application goes into hung state when pstack child process is
started. When I try to attach GDB to this hung process, its gives
error "ptrace: operation not permitted"

The /proc/<pid>/task/<taskid>status for all threads is as below
Name:   myapplcation
State:  T (tracing stop)

This indicates that gdb successfully attached to your process.

It is likely that this gdb process is now waiting for something,
though I can't imagine what for. Possibly it tries to print something
to tty (possibly some warning), and gets itself SIGSTOPped?

Can you attach a new instance of gdb the the apparently-hung
pstack/gdb process?

What is the State in /proc/<pstack-pid>/status ?

Cheers,
--
In order to understand recursion you must first understand recursion.
Remove /-nsp/ for email.

Hi Paul,

Thanks for the reply.
Following are few more details

ps -a
====
3088 29440 0 15:45 pts/5 00:00:00 /bin/sh /usr/bin/pstack 29440
3097 3088 0 15:45 pts/5 00:00:00 sed -n -e s/^(gdb) // -e /^#/p -
e /^Thread/p
29440 15781 0 May15 pts/5 00:00:01 ./myapplication
3096 3088 1 15:45 pts/5 00:00:07 gdb --quiet --readnever -nx /
proc/29440/exe 29440


Stack trace of gdb
#0 0x005a47a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
#1 0x00678dd3 in __write_nocancel () from /lib/tls/libc.so.6
#2 0x0061e89f in _IO_new_file_write () from /lib/tls/libc.so.6
#3 0x0061d31b in _IO_new_do_write () from /lib/tls/libc.so.6
#4 0x0061dfa2 in _IO_new_file_sync () from /lib/tls/libc.so.6
#5 0x006136bc in fflush () from /lib/tls/libc.so.6
#6 0x080fe16e in print_frame_info ()
#7 0x080ff5eb in parse_frame_specification ()
#8 0x0807ef6d in throw_exception ()
#9 0x0807f112 in catch_errors ()
#10 0x080ff307 in parse_frame_specification ()
#11 0x0807f52c in execute_command ()
#12 0x08101302 in save_infrun_state ()
#13 0x0807f52c in execute_command ()
#14 0x08104e40 in async_disable_stdin ()
#15 0x0810538e in async_disable_stdin ()
#16 0x081040ad in delete_file_handler ()
#17 0x08103bbb in standard_macro_lookup ()
#18 0x08104352 in gdb_do_one_event ()
#19 0x0807ef6d in throw_exception ()
#20 0x0807f112 in catch_errors ()
#21 0x080b9707 in _initialize_tui_hooks ()
#22 0x00000000 in ?? ()

/proc/<pstack-pid>/status
Name: pstack
State: S (sleeping)
SleepAVG: 68%
Tgid: 3088
Pid: 3088
PPid: 29440
TracerPid: 0
Uid: 5827 5827 5827 5827
Gid: 1000 1000 1000 1000
FDSize: 256
Groups: 1000
VmSize: 5472 kB
VmLck: 0 kB
VmRSS: 996 kB
VmData: 168 kB
VmStk: 1324 kB
VmExe: 577 kB
VmLib: 1271 kB
StaBrk: 080e3000 kB
Brk: 0972f000 kB
StaStk: bfeb8960 kB
ExecLim: 080d8000
Threads: 1
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000416203
SigIgn: 0000000000001005
SigCgt: 0000000000010002
CapInh: 0000000000000000
CapPrm: 0000000000000000
CapEff: 0000000000000000


/proc/<gdb-pid>/status

Name: gdb
State: S (sleeping)
SleepAVG: 88%
Tgid: 3096
Pid: 3096
PPid: 3088
TracerPid: 0
Uid: 5827 5827 5827 5827
Gid: 1000 1000 1000 1000
FDSize: 256
Groups: 1000
VmSize: 174804 kB
VmLck: 0 kB
VmRSS: 170508 kB
VmData: 168356 kB
VmStk: 472 kB
VmExe: 2124 kB
VmLib: 1648 kB
StaBrk: 08281000 kB
Brk: 0be9b000 kB
StaStk: bff92cb0 kB
ExecLim: 0825b000
Threads: 1
SigPnd: 0000000000000000
ShdPnd: 0000000000010000
SigBlk: 0000000000416203
SigIgn: 0000000000001000
SigCgt: 0000000000030087
CapInh: 0000000000000000
CapPrm: 0000000000000000
CapEff: 0000000000000000

/proc/<sed-pid>/status
Name: sed
State: S (sleeping)
SleepAVG: 90%
Tgid: 3097
Pid: 3097
PPid: 3088
TracerPid: 0
Uid: 5827 5827 5827 5827
Gid: 1000 1000 1000 1000
FDSize: 256
Groups: 1000
VmSize: 4816 kB
VmLck: 0 kB
VmRSS: 640 kB
VmData: 172 kB
VmStk: 1252 kB
VmExe: 40 kB
VmLib: 1252 kB
StaBrk: 08058000 kB
Brk: 08803000 kB
StaStk: bfecd130 kB
ExecLim: 08052000
Threads: 1
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000406203
SigIgn: 0000000000001001
SigCgt: 0000000000000000
CapInh: 0000000000000000
CapPrm: 0000000000000000
CapEff: 0000000000000000

Regards,
Umesh
.

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