Fix deadlock if an MSBuild task is writing to stdout #78927
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CyrusNajmabadi
approved these changes
Jun 12, 2025
JoeRobich
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Jun 12, 2025
When we switched over to communicating over a named pipe rather than stdin/stdout, we were still redirecting stdin and stdout. This had the side effect that if a build task was directly writing to standard out, the build would eventually deadlock since we weren't reading from the other side. I thought about simply not redirecting stdin/stdout, but I could imagine other problems might come up if we were to have multiple build hosts trying to share stdin/stdout. So now we'll log stdout the same way we log stderr, and explicitly close stdin so readers won't deadlock waiting for input. Fixes dotnet#78766
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This was referenced Jun 14, 2025
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When we switched over to communicating over a named pipe rather than stdin/stdout, we were still redirecting stdin and stdout. This had the side effect that if a build task was directly writing to standard out, the build would eventually deadlock since we weren't reading from the other side.
I thought about simply not redirecting stdin/stdout, but I could imagine other problems might come up if we were to have multiple build hosts trying to share stdin/stdout. So now we'll log stdout the same way we log stderr, and explicitly close stdin so readers won't deadlock waiting for input.
Fixes #78766