Re: [PATCH v4 09/12] unix-socket: disallow chdir() when creating unix domain sockets

Jeff Hostetler [off-list ref] writes:

The original problem was that chdir() is not safe in a multi-threaded
process because one thread calling chdir() will affect any concurrent
file operations (open(), mkdir(), etc.) that use relative paths.

I think Adding a fork() at this layer would just create new types of
problems.  For example, if another thread was concurrently writing to
a socket while we were setting up this new socket, we would suddenly
have 1 thread in each process now writing to that socket and the
receiver would get a mixture of output from both processes.  Right?

cf. https://pubs.opengroup.org/onlinepubs/9699919799/functions/fork.html

The fork() function shall create a new process. The new process
(child process) shall be an exact copy of the calling process
(parent process) except as detailed below:

...

 * A process shall be created with a single thread. If a
   multi-threaded process calls fork(), the new process shall
   contain a replica of the calling thread and its entire address
   space, possibly including the states of mutexes and other
   resources. Consequently, to avoid errors, the child process may
   only execute async-signal-safe operations until such time as one
   of the exec functions is called.

So, probably not.