...
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f0235ade9d0) = 8680
close(5)                                = 0
rt_sigprocmask(SIG_BLOCK, [PIPE], [], 8) = 0
rt_sigaction(SIGPIPE, {SIG_DFL, [], SA_RESTORER, 0x7f02351d2150}, {SIG_IGN, [], SA_RESTORER, 0x7f02351d2150}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigaction(SIGCHLD, {SIG_DFL, [], SA_RESTORER, 0x7f02351d2150}, {SIG_IGN, [], SA_RESTORER|SA_NOCLDWAIT, 0x7f02351d2150}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
write(1, "My child vpid: 20032376\n", 24My child vpid: 20032376
) = 24
write(1, "Single-threaded execution\n", 26Single-threaded execution
) = 26
brk(0x15f4000)                          = 0x15f4000
brk(0x15ea000)                          = 0x15ea000
select(8, [4], [4], [4], NULL)          = 1 (out [4])
select(8, [4], [4], [4], NULL)          = 1 (out [4])
write(4, "\0\0\0*\4\t\01012345678\4\10\10\10\2\4\0\0\0\10\200\n\0102003"..., 46) = 46
select(8, [4], NULL, [4], NULL8680 - Hi there!
)         = 1 (in [4])
read(4, "\0\0\0000\4\t\01012345678\4\10\10\10\2\4\0\0\0\6x\2531\1\0\0\0"..., 16384) = 52
write(1, "8679 - My child 8680 said hi\n", 298679 - My child 8680 said hi
) = 29
write(1, "Threaded execution\n", 19Threaded execution
)    = 19
rt_sigprocmask(SIG_BLOCK, ~[ILL BUS SEGV RTMIN RT_1], [], 8) = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
lseek(0, 0, SEEK_CUR)                   = -1 ESPIPE (Illegal seek)
ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
lseek(1, 0, SEEK_CUR)                   = -1 ESPIPE (Illegal seek)
ioctl(2, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
lseek(2, 0, SEEK_CUR)                   = -1 ESPIPE (Illegal seek)
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7fff55890df8) = -1 ENOTTY (Inappropriate ioctl for device)
lseek(3, 0, SEEK_CUR)                   = 700
ioctl(4, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7fff55890df8) = -1 ENOTTY (Inappropriate ioctl for device)
lseek(4, 0, SEEK_CUR)                   = -1 ESPIPE (Illegal seek)
ioctl(4, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7fff55890df8) = -1 ENOTTY (Inappropriate ioctl for device)
lseek(4, 0, SEEK_CUR)                   = -1 ESPIPE (Illegal seek)
brk(0x160b000)                          = 0x160b000
brk(0x162c000)                          = 0x162c000
brk(0x164d000)                          = 0x164d000
brk(0x166e000)                          = 0x166e000
brk(0x168f000)                          = 0x168f000
brk(0x16b1000)                          = 0x16b1000
brk(0x16d2000)                          = 0x16d2000
mmap(NULL, 135168, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f0235933000
brk(0x16f3000)                          = 0x16f3000
brk(0x1714000)                          = 0x1714000
brk(0x1735000)                          = 0x1735000
brk(0x1756000)                          = 0x1756000
brk(0x1777000)                          = 0x1777000
brk(0x1798000)                          = 0x1798000
munmap(0x7f0235933000, 135168)          = 0
mmap(NULL, 8392704, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7f0233404000
mprotect(0x7f0233404000, 4096, PROT_NONE) = 0
clone(child_stack=0x7f0233c03ff0, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x7f0233c049d0, tls=0x7f0233c04700, child_tidptr=0x7f0233c049d0) = 8681
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
futex(0x7f0233c049d0, FUTEX_WAIT, 8681, NULL<_HANGS_HERE_>