On Mon, 21 Mar 2022 11:45:57 -0700 (PDT) Jeremy Drake wrote: > This issue was reported to MSYS2 as a hang when trying to build libxml2 in > a Windows docker container. Another user was able to come up with a > simple reproducer and a reasonable theory as to why it happens. The msys2 > issue is https://github.com/msys2/msys2-runtime/issues/77, and I will > quote the reproducer and analysis here: > > I am having the same issue when building mingw. I managed to reduce the > issue to the following shell script: > > #!/bin/sh > seq 1 99999 > big_file > eval '$(eval cmd.exe /c "type big_file" | : )' > > When running as a normal user this completes immediately, but when run as > a system service it hangs forever. The issue appears to be that when > running under the SYSTEM account, the third sh process holds open the read > end of the pipe. Since cmd has too much output to write all at once, it > waits until the pipe's buffer has room to write more, but since sh isn't > actually reading from the pipe, this hangs forever. When running as a > normal user the read end of the pipe is not kept open, and so cmd.exe gets > an error when attempting to write and exits immediately. > > My suspicion is that this is caused by f79a461 (which keeps the read end > of the pipe open) and b531d6b (which changes the behavior depending on > whether or not the program is running as a service).
Thanks for the report. This is expected problem as mentioned in b531d6b commit message. However, I could not imagin the situation that the service has multiple writer for the pipe and one of them is a non-cygwin app. Question is: Does the docker invoke the command using SYSTEM account? Or is the processes in docker determined as running as a service? -- Takashi Yano <takashi.y...@nifty.ne.jp> -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
