Removed duplicate threading topics #8164
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I'm sorry that it took me so long to get to this, @pkulikov. Thanks for doing this, as well as for all of the work you've done on improving and consolidating the threading docs. This looks very good. I thought, though, that two paragraphs from both the C# and the VB top-level topic were worthwhile to incorporate in the .NET Guide's overview topic. Let me know what you think, or whether I've simply overlooked a comparable discussion in the .NET Guide.
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| - Threads share the application's resources. For more information, see [Using Threads and Threading](../../../../../docs/standard/threading/using-threads-and-threading.md). | ||
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| By default, a C# program has one thread. However, auxiliary threads can be created and used to execute code in parallel with the primary thread. These threads are often called *worker threads*. |
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It seems to me that this and the next paragraph provide useful context but do not seem to appear in the overview at https://docs.microsoft.com/dotnet/standard/threading/threads-and-threading. I think that that topic could benefit from having these two paragraphs added, and also could be broken up into sections. Currently, there's only "When to use multiple threads". This could go first ("Threads and worker threads"), followed by "Threads, application domains, and processes", followed by the multiple threads topic.
A bit of rewording and rewriting would also be needed to make the topic flow smoothly.
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@rpetrusha I agree, I'll use the opportunity and take a look on how to improve the linked article.
…m/pkulikov/docs into remove-threading-duplicate-topics
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@rpetrusha I've traveled some rabbit holes, so the article update has taken a while. First, I've rewritten the "Threads and threading" article trying to keep the original message passed. My intent was to keep the content as general as possible, so I've removed the details that can be found in the referenced articles. The new Processes and threads section is based on the Windows docs When I've worked on the When to use multiple threads, I've realized that the Number of processors section in the "Managed threading best practices" article doesn't add a lot to the best practices. Instead, I've highlighted the difference between single/multi core systems in the new version of the "Threads and threading" article. One more reason why I've removed the "Number of processors" section is that it goes into too much technical details, which do not help a lot to write multithreading code. Moreover, when one is developing code, one usually doesn't know the number of processors on the target machine, and frankly, should not rely on it. This PR is ready for another review. I might have missed or removed some important bits. If that's the case, please let me know. |
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ping @rpetrusha |
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| Race conditions can also occur when you synchronize the activities of multiple threads. Whenever you write a line of code, you must consider what might happen if a thread were preempted before executing the line (or before any of the individual machine instructions that make up the line), and another thread overtook it. | ||
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| ## Number of Processors |
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I think that this content is much less important than it once was, but it still can be important. It's worth adding a short Number of processors section after the Static members section that says something like, "Whether there are multiple processors or only one processor available on a system can influence multithreaded architecture. For more information, see [Number of Processors](https://docs.microsoft.com/en-us/previous-versions/dotnet/netframework-1.1/1c9txz50(v%3dvs.71)#number-of-processors). You can determine the number of processors available at runtime by retrieving the value of the <xref:System.Environment.ProcessorCount?displayProperty=nameWithType> property.
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The link to the ProcessorCount property is a good addition. Thanks!
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| > In the .NET Framework versions 1.0 and 1.1, the common language runtime silently traps some exceptions, for example in thread pool threads. This may corrupt application state and eventually cause applications to hang, which might be very difficult to debug. | ||
| > The .NET Framework provides a way to isolate applications within a process with the use of *application domains*. For more information, see the [Application domains and threads](../../framework/app-domains/application-domains.md#application-domains-and-threads) section of the [Application domains](../../framework/app-domains/application-domains.md) article. |
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I wonder if the fact that app domains are only available on .NET Framework needs to be made clearer, perhaps by adding "(Application domains are not available on .NET Core>)" after the first sentence?
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| ## Processes and threads | ||
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| A *process* is an executing program. An operating system uses processes to separate the applications that are being executed. A *thread* is the basic unit to which an operating system allocates processor time. Multiple threads can run in the context of a process. All threads of a process share its virtual address space. A thread can execute any part of the program code, including parts currently being executed by another thread. |
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I think some of the basic information on what a thread is should be added back before the "Multiple threads..." sentence. Particularly: "Each thread maintains exception handlers, a scheduling priority, and a set of structures the system uses to save the thread context until it is scheduled. The thread context includes all the information the thread needs to seamlessly resume execution, including the thread's set of CPU registers and stack, in the address space of the thread's host process."
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@rpetrusha I've put those sentences back, rephrased and with some information dropped. However, I hope that the essence is there. Please let me know, if it's not true and I'll come up with better phrasing.
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@rpetrusha I've addressed your feedback. Please check the latest commit and the comments I've left. Thanks for review! |
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I think that this looks really good, @pkulikov. Thanks for the last set of revisions, as well as for your patience. I'll merge now. |
This PR removes the last bits of the duplicate threading guides:
https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/threading/
https://docs.microsoft.com/en-us/dotnet/visual-basic/programming-guide/concepts/threading/
and redirects them to the .NET threading guide:
https://docs.microsoft.com/en-us/dotnet/standard/threading/
Fixes #6180
@rpetrusha please review.