Debug with strace and ltrace

Question

My program hung and I decided to ltrace and strace it.

strace -p pid

gives me an "infinite" printing on screen :

lseek(3, 57114624, SEEK_SET)            = 57114624
read(3, "\r\r\207\0\n\6O\0\16b\f\277\v\370\v1\ni\tm\10\245\7\335\7\25\6O\5v\5v"..., 4096) = 4096
lseek(3, 57118720, SEEK_SET)            = 57118720
read(3, "\r\1(\0\21\0`\0\0174\16l\r\246\f\336\f\26\vO\n\207\t\277\10\371\6\233\5\323\5\v"..., 4096) = 4096
...

ltrace -p pid Gives the same "infinite" printing:

memcmp(0x12efab68, 0x12eface8, 15, 0x12eface8)                                      = 0xfffffff8
memset(0x12fa48e0, '\0', 72)                                                        = 0x12fa48e0
memset(0x12fa4928, '\0', 144)                                                       = 0x12fa4928
lseek64(3, 0x2c30000, 0, 0x2c30000)                                                 = 0x2c30000
memcpy(0x12efab68, "DIRAC.HLTFarm.lhcb", 18)                                        = 0x12efab68
memcmp(0x12efab68, 0x12eface8, 15, 0x12eface8)                                      = 0xfffffff8
memcpy(0x12efab68, "DIRAC.HLTFarm.lhcb", 18^C)                                        = 0x12efab68

What conclusions based on these results I can do about what is going on with program?

Answer 1

Attach a debugger (with gdb -p pid) and obtain a backtrace (with the bt command). This will tell you in more detail where the program is spinning. You may have to install debugging information to get a useful backtrace.