From 6cb107452a5a5551a04baf6bc4ff0b8299dfb596 Mon Sep 17 00:00:00 2001 From: Keith Randall Date: Tue, 24 Sep 2024 15:11:54 -0700 Subject: [PATCH] runtime: print fatal messages without interleaving Grab the print lock around the set of prints we use to report fatal errors. This ensures that each fatal error gets reported atomically instead of interleaved with other fatal errors. Fixes #69447 Change-Id: Ib3569f0c8210fd7e19a7d8ef4bc114f07469f317 Reviewed-on: https://go-review.googlesource.com/c/go/+/615655 Auto-Submit: Keith Randall Reviewed-by: Michael Pratt Reviewed-by: Keith Randall LUCI-TryBot-Result: Go LUCI --- src/runtime/crash_test.go | 30 +++++++++++++++++++++++++++--- src/runtime/panic.go | 2 ++ 2 files changed, 29 insertions(+), 3 deletions(-) diff --git a/src/runtime/crash_test.go b/src/runtime/crash_test.go index 69e1034ff8..52d33b8f58 100644 --- a/src/runtime/crash_test.go +++ b/src/runtime/crash_test.go @@ -621,7 +621,7 @@ func TestConcurrentMapWrites(t *testing.T) { } testenv.MustHaveGoRun(t) output := runTestProg(t, "testprog", "concurrentMapWrites") - want := "fatal error: concurrent map writes" + want := "fatal error: concurrent map writes\n" if !strings.HasPrefix(output, want) { t.Fatalf("output does not start with %q:\n%s", want, output) } @@ -632,7 +632,7 @@ func TestConcurrentMapReadWrite(t *testing.T) { } testenv.MustHaveGoRun(t) output := runTestProg(t, "testprog", "concurrentMapReadWrite") - want := "fatal error: concurrent map read and map write" + want := "fatal error: concurrent map read and map write\n" if !strings.HasPrefix(output, want) { t.Fatalf("output does not start with %q:\n%s", want, output) } @@ -643,12 +643,36 @@ func TestConcurrentMapIterateWrite(t *testing.T) { } testenv.MustHaveGoRun(t) output := runTestProg(t, "testprog", "concurrentMapIterateWrite") - want := "fatal error: concurrent map iteration and map write" + want := "fatal error: concurrent map iteration and map write\n" if !strings.HasPrefix(output, want) { t.Fatalf("output does not start with %q:\n%s", want, output) } } +func TestConcurrentMapWritesIssue69447(t *testing.T) { + testenv.MustHaveGoRun(t) + exe, err := buildTestProg(t, "testprog") + if err != nil { + t.Fatal(err) + } + for i := 0; i < 200; i++ { + output := runBuiltTestProg(t, exe, "concurrentMapWrites") + if output == "" { + // If we didn't detect an error, that's ok. + // This case makes this test not flaky like + // the other ones above. + // (More correctly, this case makes this test flaky + // in the other direction, in that it might not + // detect a problem even if there is one.) + continue + } + want := "fatal error: concurrent map writes\n" + if !strings.HasPrefix(output, want) { + t.Fatalf("output does not start with %q:\n%s", want, output) + } + } +} + type point struct { x, y *int } diff --git a/src/runtime/panic.go b/src/runtime/panic.go index 5b62e019d9..d70d567912 100644 --- a/src/runtime/panic.go +++ b/src/runtime/panic.go @@ -1081,6 +1081,7 @@ func throw(s string) { func fatal(s string) { // Everything fatal does should be recursively nosplit so it // can be called even when it's unsafe to grow the stack. + printlock() // Prevent multiple interleaved fatal reports. See issue 69447. systemstack(func() { print("fatal error: ") printindented(s) // logically printpanicval(s), but avoids convTstring write barrier @@ -1088,6 +1089,7 @@ func fatal(s string) { }) fatalthrow(throwTypeUser) + printunlock() } // runningPanicDefers is non-zero while running deferred functions for panic. -- 2.48.1