Prevent dangling cat-file calls (goroutine alternative) (#19454)

If an `os/exec.Command` is passed non `*os.File` as an input/output, go
will create `os.Pipe`s and wait for their closure in `cmd.Wait()`.  If
the code following this is responsible for closing `io.Pipe`s or other
handlers then on process death from context cancellation the `Wait` can
hang.

There are two possible solutions:

1. use `os.Pipe` as the input/output as `cmd.Wait` does not wait for these.
2. create a goroutine waiting on the context cancellation that will close the inputs.

This PR provides the second option - which is a simpler change that can
be more easily backported.

Closes #19448

Signed-off-by: Andrew Thornton <art27@cantab.net>
This commit is contained in:
zeripath 2022-04-22 16:20:04 +01:00 committed by GitHub
parent 0dfc2e55ea
commit 0dcc74a8a7
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@ -57,6 +57,12 @@ func CatFileBatchCheck(ctx context.Context, repoPath string) (WriteCloserError,
<-closed
}
// Ensure cancel is called as soon as the provided context is cancelled
go func() {
<-ctx.Done()
cancel()
}()
_, filename, line, _ := runtime.Caller(2)
filename = strings.TrimPrefix(filename, callerPrefix)
@ -101,6 +107,12 @@ func CatFileBatch(ctx context.Context, repoPath string) (WriteCloserError, *bufi
<-closed
}
// Ensure cancel is called as soon as the provided context is cancelled
go func() {
<-ctx.Done()
cancel()
}()
_, filename, line, _ := runtime.Caller(2)
filename = strings.TrimPrefix(filename, callerPrefix)