runtime: print pointers being put in checkPut

In order to further diagnose #27993, I need to see exactly what
pointers are being added to the gcWork buffer too late.

Change-Id: I8d92113426ffbc6e55d819c39e7ab5eafa68668d
Reviewed-on: https://go-review.googlesource.com/c/152957
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

diff --git a/src/runtime/mgcwork.go b/src/runtime/mgcwork.go
index 8a77ff55e4d1d9f021ba80ecf31171352557f6b1..cdc94b8ffb11ee525001edc750bb7602a28021d6 100644 (file)
--- a/src/runtime/mgcwork.go
+++ b/src/runtime/mgcwork.go
@@ -115,11 +115,19 @@ func (w *gcWork) init() {
        w.wbuf2 = wbuf2
 }
 
-func (w *gcWork) checkPut() {
+func (w *gcWork) checkPut(ptr uintptr, ptrs []uintptr) {
        if debugCachedWork {
                for atomic.Load(&gcWorkPauseGen) == w.pauseGen {
                }
                if throwOnGCWork {
+                       printlock()
+                       println("runtime: late gcWork put")
+                       if ptr != 0 {
+                               gcDumpObject("ptr", ptr, ^uintptr(0))
+                       }
+                       for _, ptr := range ptrs {
+                               gcDumpObject("ptrs", ptr, ^uintptr(0))
+                       }
                        throw("throwOnGCWork")
                }
        }
@@ -129,7 +137,7 @@ func (w *gcWork) checkPut() {
 // obj must point to the beginning of a heap object or an oblet.
 //go:nowritebarrierrec
 func (w *gcWork) put(obj uintptr) {
-       w.checkPut()
+       w.checkPut(obj, nil)
 
        flushed := false
        wbuf := w.wbuf1
@@ -165,7 +173,7 @@ func (w *gcWork) put(obj uintptr) {
 // otherwise it returns false and the caller needs to call put.
 //go:nowritebarrierrec
 func (w *gcWork) putFast(obj uintptr) bool {
-       w.checkPut()
+       w.checkPut(obj, nil)
 
        wbuf := w.wbuf1
        if wbuf == nil {
@@ -188,7 +196,7 @@ func (w *gcWork) putBatch(obj []uintptr) {
                return
        }
 
-       w.checkPut()
+       w.checkPut(0, obj)
 
        flushed := false
        wbuf := w.wbuf1
@@ -311,12 +319,12 @@ func (w *gcWork) balance() {
                return
        }
        if wbuf := w.wbuf2; wbuf.nobj != 0 {
-               w.checkPut()
+               w.checkPut(0, wbuf.obj[:wbuf.nobj])
                putfull(wbuf)
                w.flushedWork = true
                w.wbuf2 = getempty()
        } else if wbuf := w.wbuf1; wbuf.nobj > 4 {
-               w.checkPut()
+               w.checkPut(0, wbuf.obj[:wbuf.nobj])
                w.wbuf1 = handoff(wbuf)
                w.flushedWork = true // handoff did putfull
        } else {