Here is what I don't understand from what you said. "The child process is created with a single thread—the one that called fork()." To me that implies that the thread that called fork() is the same thread as the child process. I guess you're talking about the distinction between logical threads and physical threads.
But the main issue is your suggestion that I should call fork-execv from the thread that runs the main C program, not from a separate physical pthread. That would certainly eliminate the overhead of creating a new pthread. I am working now to finish this, and I will try your suggestion of calling fork-execv from the "main" thread. When I reply back next I can give you a complete picture of what I'm doing. Your comments, and those of Peter Holzer and Chris Angelico, are most appreciated. Dec 6, 2021, 10:37 by ba...@barrys-emacs.org: > > >> On 6 Dec 2021, at 17:09, Jen Kris via Python-list <python-list@python.org> >> wrote: >> >> I can't find any support for your comment that "Fork creates a new >> process and therefore also a new thread." From the Linux man pages >> https://www.man7.org/linux/man-pages/man2/fork.2.html, "The child process is >> created with a single thread—the one that called fork()." >> > > You just quoted the evidence! > > All new processes on unix (may all OS) only ever have one thread when they > start. > The thread-id of the first thread is the same as the process-id and referred > to as the main thread. > >> >> I have a one-core one-thread instance at Digital Ocean available running >> Ubuntu 18.04. I can fork and create a new process on it, but it doesn't >> create a new thread because it doesn't have one available. >> > > > By that logic it can only run one process... > > It has one hardware core that support one hardware thread. > Linux can create as many software threads as it likes. > >> You may also want to see "Forking vs Threading" >> (https://www.geekride.com/fork-forking-vs-threading-thread-linux-kernel), >> "Fork vs Thread" >> (https://medium.com/obscure-system/fork-vs-thread-38e09ec099e2), and "Linux >> process and thread" (https://zliu.org/post/linux-process-and-thread) ("This >> means that to create a normal process fork() is used that further calls >> clone() with appropriate arguments while to create a thread or LWP, a >> function from pthread library calls clone() with relvant flags. So, the main >> difference is generated by using different flags that can be passed to >> clone() funciton(to be exact, it is a system call"). >> >> You may be confused by the fact that threads are called light-weight >> processes. >> > > No Peter and I are not confused. > >> >> Or maybe I'm confused :) >> > > Yes you are confused. > >> >> If you have other information, please let me know. Thanks. >> > > Please get the book I recommended, or another that covers systems programming > on unix, and have a read. > > Barry > >> >> Jen >> >> >> Dec 5, 2021, 18:08 by hjp-pyt...@hjp.at: >> >>> On 2021-12-06 00:51:13 +0100, Jen Kris via Python-list wrote: >>> >>>> The C program creates two threads (using pthreads), one for itself and >>>> one for the child process. On creation, the second pthread is pointed >>>> to a C program that calls fork-execv to run the Python program. That >>>> way Python runs on a separate thread. >>>> >>> >>> I think you have the relationship between processes and threads >>> backwards. A process consists of one or more threads. Fork creates a new >>> process and therefore also a new thread. >>> >>> hp >>> >>> -- >>> _ | Peter J. Holzer | Story must make more sense than reality. >>> |_|_) | | >>> | | | h...@hjp.at | -- Charles Stross, "Creative writing >>> __/ | http://www.hjp.at/ | challenge!" >>> >> >> -- >> https://mail.python.org/mailman/listinfo/python-list >> -- https://mail.python.org/mailman/listinfo/python-list
