commandserver: add new forking server implemented without using SocketServer
SocketServer.ForkingMixIn of Python 2.x has a couple of issues, such as:
- race condition that leads to 100% CPU usage (Python 2.6)
https://bugs.python.org/
issue21491
- can't wait for children belonging to different process groups (Python 2.6)
- leaves at least one zombie process (Python 2.6, 2.7)
https://bugs.python.org/
issue11109
The first two are critical because we do setpgid(0, 0) in child process to
isolate terminal signals. The last one isn't, but ForkingMixIn seems to be
doing silly. So there are two choices:
a) backport and maintain SocketServer until we can drop support for Python 2.x
b) replace SocketServer by simpler one and eliminate glue codes
I chose (b) because it's great time for getting rid of utterly complicated
SocketServer stuff, and preparing for future move towards prefork service.
New unixforkingservice is implemented loosely based on chg
531f8ef64be6. It
is monolithic but much simpler than SocketServer. unixservicehandler provides
customizing points for chg, and it will be shared with future prefork service.
Old unixservice class is still used by chgserver. It will be removed later.
Thanks to Jun Wu for investigating these issues.
commandserver: extract function that serves for the current connection
This will be used by new server implementation.
commandserver: manually create file objects from socket
Prepares for moving away from SocketServer. See the subsequent patches for
why.
bdiff: use ssize_t in favor of Py_ssize_t in cpython-unaware locations
This function and struct will be exposed via cffi, so we need to
remove the cpython API dependency they currently have.
hgweb: enumerate lines in loop header, not before
Doing this will allow access to the lines in arbitrary order (because the
result of enumerate() is an iterator), and that will help calculating rowspan
for annotate blocks.