cmd/compile: fix deadlock on syntax error

Fixes golang#52127

Change-Id: I6523c83350cb9263d23e3e8b472fe63a5cc99c2e
Reviewed-on: https://go-review.googlesource.com/c/go/+/398014
Reviewed-by: Matthew Dempsky <[email protected]>
Run-TryBot: Matthew Dempsky <[email protected]>
Auto-Submit: Matthew Dempsky <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Trust: Cherry Mui <[email protected]>

Author: hopehook

src/cmd/compile/internal/noder/noder.go

@@ -33,29 +33,34 @@ func LoadPackage(filenames []string) {
 	sem := make(chan struct{}, runtime.GOMAXPROCS(0)+10)
 
 	noders := make([]*noder, len(filenames))
-	for i, filename := range filenames {
+	for i := range noders {
 		p := noder{
 			err: make(chan syntax.Error),
 		}
 		noders[i] = &p
+	}
 
-		filename := filename
-		go func() {
+	go func() {
+		for i, filename := range filenames {
+			filename := filename
+			p := noders[i]
 			sem <- struct{}{}
-			defer func() { <-sem }()
-			defer close(p.err)
-			fbase := syntax.NewFileBase(filename)
-
-			f, err := os.Open(filename)
-			if err != nil {
-				p.error(syntax.Error{Msg: err.Error()})
-				return
-			}
-			defer f.Close()
+			go func() {
+				defer func() { <-sem }()
+				defer close(p.err)
+				fbase := syntax.NewFileBase(filename)
+
+				f, err := os.Open(filename)
+				if err != nil {
+					p.error(syntax.Error{Msg: err.Error()})
+					return
+				}
+				defer f.Close()
 
-			p.file, _ = syntax.Parse(fbase, f, p.error, p.pragma, mode) // errors are tracked via p.error
-		}()
-	}
+				p.file, _ = syntax.Parse(fbase, f, p.error, p.pragma, mode) // errors are tracked via p.error
+			}()
+		}
+	}()
 
 	var lines uint
 	for _, p := range noders {