[release-branch.go1.10] runtime: don't check for String/Error methods in printany

They have either already been called by preprintpanics, or they can
not be called safely because of the various conditions checked at the
start of gopanic.

Fixes #24059

Change-Id: I4a6233d12c9f7aaaee72f343257ea108bae79241
Reviewed-on: https://go-review.googlesource.com/96755
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-on: https://go-review.googlesource.com/102781
Run-TryBot: Andrew Bonventre <andybons@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/runtime/error.go b/src/runtime/error.go
index 6048272e75d40ca83ae182bc3a6ebf8b81f0f32a..e1291e15435d53fc79b95f34c0e52065bc2f020d 100644 (file)
--- a/src/runtime/error.go
+++ b/src/runtime/error.go
@@ -73,14 +73,12 @@ func typestring(x interface{}) string {
 }
 
 // printany prints an argument passed to panic.
+// If panic is called with a value that has a String or Error method,
+// it has already been converted into a string by preprintpanics.
 func printany(i interface{}) {
        switch v := i.(type) {
        case nil:
                print("nil")
-       case stringer:
-               print(v.String())
-       case error:
-               print(v.Error())
        case bool:
                print(v)
        case int:

diff --git a/src/runtime/iface.go b/src/runtime/iface.go
index 7c5d3a05b25c97d63b06ee6a243fbc6d514fe944..bd6bc282f4eec3789e14220d5a83ca5b599cc047 100644 (file)
--- a/src/runtime/iface.go
+++ b/src/runtime/iface.go
@@ -113,6 +113,14 @@ func (t *itabTableType) find(inter *interfacetype, typ *_type) *itab {
 // itabAdd adds the given itab to the itab hash table.
 // itabLock must be held.
 func itabAdd(m *itab) {
+       // Bugs can lead to calling this while mallocing is set,
+       // typically because this is called while panicing.
+       // Crash reliably, rather than only when we need to grow
+       // the hash table.
+       if getg().m.mallocing != 0 {
+               throw("malloc deadlock")
+       }
+
        t := itabTable
        if t.count >= 3*(t.size/4) { // 75% load factor
                // Grow hash table.

diff --git a/src/runtime/panic.go b/src/runtime/panic.go
index c51948bd18e5805d745596237cf3a76adfd0933b..3d0c85f7f9327a72987f2681b443b96b9416c261 100644 (file)
--- a/src/runtime/panic.go
+++ b/src/runtime/panic.go
@@ -389,7 +389,6 @@ func Goexit() {
 
 // Call all Error and String methods before freezing the world.
 // Used when crashing with panicking.
-// This must match types handled by printany.
 func preprintpanics(p *_panic) {
        defer func() {
                if recover() != nil {
@@ -415,8 +414,6 @@ func printpanics(p *_panic) {
                print("\t")
        }
        print("panic: ")
-       // Because of preprintpanics, p.arg cannot be an error or
-       // stringer, so this won't call into user code.
        printany(p.arg)
        if p.recovered {
                print(" [recovered]")