Syscalls traced by truss.


Parent process:

 1436: unlink("fifo_5950861521")                 ERR#2 'No such file or directory'
 1436: open("fifo_5950861521",O_WRONLY|O_CLOEXEC,00) ERR#4 'Interrupted system call'
 1436: open("fifo_5950861521",O_WRONLY|O_CLOEXEC,00) ERR#4 'Interrupted system call'
 ...
 1436: open("fifo_5950861521",O_WRONLY|O_CLOEXEC,00) ERR#4 'Interrupted system call'


Child process:

 2689: open("fifo_5950861521",O_CLOEXEC,00)      = 3 (0x3)
 2689: close(3)                                  ERR#4 'Interrupted system call'


Hum, it looks like the child process gets signals, many syscalls are interrupted by signals. In my simple test, 7 syscalls were interrupted by signals in the child process. I didn't expect "setitimer" to be inherited by subprocess.Popen.

The suspicious thing is that close() fails with EINTR in the child process and it is not retried.