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Because that OS best practices is to use threads. Traditionally Windows applications that create processes all the time come from UNIX heritage. Contrary to U
by pjmlp 5mo ago
Because that OS best practices is to use threads.
Traditionally Windows applications that create processes all the time come from UNIX heritage.
Contrary to UNIX, Windows NT was designed with threads first mentality, from the get go.
While on UNIX they were added after fact, and to this day there are gotchas mixing posix threads with signals, fork and exec.
- zozbot234 5mo agoWindows was designed with threads-first mentality because on pre-386 machines you don't have viable process memory protection, so your tasks share memory by necessity. This is not a great argument.
- JdeBP 5mo agoWindows NT was never designed with pre-386 machines in mind. That was the territory of the old DOS+Windows. Windows NT from the get-go was for machines with page-based virtual memory. * https://computernewb.com/~lily/files/Documents/NTDesignWorkbook/vm.pdf https://computernewb.com/~lily/files/Documents/NTDesignWorkb...
- pstuart 5mo agoWinNT 3.5 was a solid offering.
- epcoa 5mo agoThis is not true. NT never had fork, was always based on the assumption of an MMU and Dave Cutler was a well known fork hater in the 80s long before this paper came out and made it cool to be so. By the time Windows 95 was out, the baseline was 386 with an MMU. CreateThread was initially designed for NT in 1993 though (which didn’t support pre-386 CPUs).
- JdeBP 5mo agoAs mentioned elsewhere on this page, Windows NT had fork from the start. Vide NtCreateProcess and what happens if an image file is not explicitly supplied. * https://computernewb.com/~lily/files/Documents/NTDesignWorkbook/proc.pdf https://computernewb.com/~lily/files/Documents/NTDesignWorkb...
- dcrazy 5mo agoNtCreateProcess doesn’t accept an image file parameter.
- JdeBP 5mo agoYou haven't read the doco. I did point to some. The image file is supplied (or not) via the section object. Think it through. Windows NT supported fork from the start in its POSIX subsystem, that subsystem was layered on top of the Native API, and this is the Native API mechanism that the POSIX subsystem employed. Although it took until Gary Nebbett for someone to publicly show how, even though people knew informally back in 1993.
- epcoa 5mo agoNtCreateProcess was not a public Windows API. NT was flexible, that’s not what was being discussed, which should have been clear from the context.
- keitmo 5mo agoNT performed unnatural acts to implement fork semantics for the POSIX subsystem.
- deleted 5mo ago[deleted]
- pjmlp 5mo agoWindows NT! Misread on purpose to make a point?
- dcrazy 5mo agoNT was designed to be platform-agnostic, and its original target was the DEC Alpha. Its process model owes nothing to pre-386 CPUs. The WinAPI CreateProcess function is a layer atop NtCreateProcess, so that is where the pre-386 heritage lives. But even the WinAPI process model changed significantly with 32-bit Windows.
- peterfirefly 5mo agoNo. https://en.wikipedia.org/wiki/Windows_NT#Development https://en.wikipedia.org/wiki/Windows_NT#Development Windows NT was developed on various different CPUs before the Alpha was a thing. When it was released in 1993, it was released for three CPUs: IA-32, MIPS, and Alpha.
- dcrazy 5mo agoSorry, I had conflated Windows NT development with development of 64-bit Windows as told by Raymond Chen: https://learn.microsoft.com/en-us/previous-versions/technet-magazine/cc718978(v=msdn.10) https://learn.microsoft.com/en-us/previous-versions/technet-... Raymond also says elsewhere that most WinNT engineers did development on i386, but doesn’t explicitly say what time period he is describing: https://devblogs.microsoft.com/oldnewthing/20250513-00/?p=111176 https://devblogs.microsoft.com/oldnewthing/20250513-00/?p=11...
- PaulDavisThe1st 5mo agoA more accurate way to describe this is that Windows' (NT onward) core execution context model is a bunch of threads that by default share memory, whereas Unixen have a core task context model of a bunch of threads that by default do not share memory. Both systems are implemented using threads as the execution context, but in Unix, the history means that that you fork+exec most of the time, resulting in a two tasks that do not share memory any more. By contrast, on Windows (NT onward) the common case when creating a new execution context is to create a thread that shares memory with others in its process. Both systems allow the easy use of the other's core abstraction. On Unix, you can either code like its 1986 and use fork without exec, or use clone(3) or any of its higher level abstractions like pthreads. You're right that POSIX semantics get tangled when using threads.
- snozolli 5mo agowhereas Unixen have a core task context model of a bunch of threads that by default do not share memory. How are those not simply child processes? I don't understand your use of the word 'threads' here. Does the Unix world not distinguish between threads and processes? In Win32, threads exist within processes, and you can create new threads or child processes.
- pjmlp 5mo agoActually on Windows a process is a thread with additional information. The unit of execution is the thread. On the UNIX world it depends on which UNIX you are talking about. Linux has a similar model to Windows NT nowadays, hence clone() as key primitive. Other UNIXes have different approaches.
- PaulDavisThe1st 5mo agoI worked on the kernel of DEC Ultrix, Mach/BSD and a couple of other early Unixen. The approach in all the ones I worked on was broadly the same.
- trumpdong 5mo ago
- knome 5mo agothe only difference between a thread and a process on linux is how many structures they share. the function is identical.
- pjmlp 5mo agoAgreed, however not all UNIXes are like Linux.
- sunshowers 5mo agoThe problem is that threads are not fault boundaries but processes are. So they're not interchangeable when you care about resilience and misbehaving code.
- pjmlp 5mo agoTrue, but on Windows the approach is then to use COM servers, which have a faster IPC model, and can even serve multiple clients, depending on how the appartement space is configured.
- mort96 5mo ago"Faster IPC model" than what? Faster than writing to and reading from a pipe? Faster than POSIX shared memory?
- pjmlp 5mo agoThan UNIX fork/exec model, or calling into Create Process all the time. Windows has a more rich set of IPC stuff than POSIX, especially since it has a microkernel like design. If you are going to say it is everything on the same memory space anyway, it isn't. Optional on Windows 10, and enforced on Windows 11, Hyper-V is always running, and several components including kernel and driver modules are sandboxed into their little worlds. Several additional sandboxing changes were announced at BUILD.
- nine_k 5mo agoPOSIX threads having problems with signals is, imho, mostly the problem with signals in general. They are pretty poorly designed: https://lwn.net/Articles/414618/ https://lwn.net/Articles/414618/