1 files changed, 39 insertions, 12 deletions

diff --git a/libgo/go/net/http/pprof/pprof.go b/libgo/go/net/http/pprof/pprof.go
index 05d0890fdf3..12c7599ab0f 100644
--- a/libgo/go/net/http/pprof/pprof.go
+++ b/libgo/go/net/http/pprof/pprof.go
@@ -37,6 +37,11 @@
 //
 //	wget http://localhost:6060/debug/pprof/trace?seconds=5
 //
+// Or to look at the holders of contended mutexes, after calling
+// runtime.SetMutexProfileFraction in your program:
+//
+//	go tool pprof http://localhost:6060/debug/pprof/mutex
+//
 // To view all available profiles, open http://localhost:6060/debug/pprof/
 // in your browser.
 //
@@ -57,6 +62,7 @@ import (
 	"os"
 	"runtime"
 	"runtime/pprof"
+	"runtime/trace"
 	"strconv"
 	"strings"
 	"time"
@@ -89,6 +95,11 @@ func sleep(w http.ResponseWriter, d time.Duration) {
 	}
 }
 
+func durationExceedsWriteTimeout(r *http.Request, seconds float64) bool {
+	srv, ok := r.Context().Value(http.ServerContextKey).(*http.Server)
+	return ok && srv.WriteTimeout != 0 && seconds >= srv.WriteTimeout.Seconds()
+}
+
 // Profile responds with the pprof-formatted cpu profile.
 // The package initialization registers it as /debug/pprof/profile.
 func Profile(w http.ResponseWriter, r *http.Request) {
@@ -97,6 +108,14 @@ func Profile(w http.ResponseWriter, r *http.Request) {
 		sec = 30
 	}
 
+	if durationExceedsWriteTimeout(r, float64(sec)) {
+		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+		w.Header().Set("X-Go-Pprof", "1")
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprintln(w, "profile duration exceeds server's WriteTimeout")
+		return
+	}
+
 	// Set Content Type assuming StartCPUProfile will work,
 	// because if it does it starts writing.
 	w.Header().Set("Content-Type", "application/octet-stream")
@@ -105,6 +124,7 @@ func Profile(w http.ResponseWriter, r *http.Request) {
 		// Can change header back to text content
 		// and send error code.
 		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+		w.Header().Set("X-Go-Pprof", "1")
 		w.WriteHeader(http.StatusInternalServerError)
 		fmt.Fprintf(w, "Could not enable CPU profiling: %s\n", err)
 		return
@@ -122,20 +142,28 @@ func Trace(w http.ResponseWriter, r *http.Request) {
 		sec = 1
 	}
 
+	if durationExceedsWriteTimeout(r, sec) {
+		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+		w.Header().Set("X-Go-Pprof", "1")
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprintln(w, "profile duration exceeds server's WriteTimeout")
+		return
+	}
+
 	// Set Content Type assuming trace.Start will work,
 	// because if it does it starts writing.
 	w.Header().Set("Content-Type", "application/octet-stream")
-	w.Write([]byte("tracing not yet supported with gccgo"))
-	// if err := trace.Start(w); err != nil {
-	// 	// trace.Start failed, so no writes yet.
-	// 	// Can change header back to text content and send error code.
-	// 	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
-	// 	w.WriteHeader(http.StatusInternalServerError)
-	// 	fmt.Fprintf(w, "Could not enable tracing: %s\n", err)
-	// 	return
-	// }
-	// sleep(w, time.Duration(sec*float64(time.Second)))
-	// trace.Stop()
+	if err := trace.Start(w); err != nil {
+		// trace.Start failed, so no writes yet.
+		// Can change header back to text content and send error code.
+		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+		w.Header().Set("X-Go-Pprof", "1")
+		w.WriteHeader(http.StatusInternalServerError)
+		fmt.Fprintf(w, "Could not enable tracing: %s\n", err)
+		return
+	}
+	sleep(w, time.Duration(sec*float64(time.Second)))
+	trace.Stop()
 }
 
 // Symbol looks up the program counters listed in the request,
@@ -207,7 +235,6 @@ func (name handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		runtime.GC()
 	}
 	p.WriteTo(w, debug)
-	return
 }
 
 // Index responds with the pprof-formatted profile named by the request.