1 files changed, 47 insertions, 32 deletions

diff --git a/src/runtime/heapdump.go b/src/runtime/heapdump.go
index 4c35309211..33e224d587 100644
--- a/src/runtime/heapdump.go
+++ b/src/runtime/heapdump.go
@@ -20,8 +20,19 @@ import (
 func runtime_debug_WriteHeapDump(fd uintptr) {
 	stopTheWorld("write heap dump")
 
+	// Keep m on this G's stack instead of the system stack.
+	// Both readmemstats_m and writeheapdump_m have pretty large
+	// peak stack depths and we risk blowing the system stack.
+	// This is safe because the world is stopped, so we don't
+	// need to worry about anyone shrinking and therefore moving
+	// our stack.
+	var m MemStats
 	systemstack(func() {
-		writeheapdump_m(fd)
+		// Call readmemstats_m here instead of deeper in
+		// writeheapdump_m because we might blow the system stack
+		// otherwise.
+		readmemstats_m(&m)
+		writeheapdump_m(fd, &m)
 	})
 
 	startTheWorld()
@@ -539,36 +550,40 @@ func dumpms() {
 	}
 }
 
-func dumpmemstats() {
+//go:systemstack
+func dumpmemstats(m *MemStats) {
+	// These ints should be identical to the exported
+	// MemStats structure and should be ordered the same
+	// way too.
 	dumpint(tagMemStats)
-	dumpint(memstats.alloc)
-	dumpint(memstats.total_alloc)
-	dumpint(memstats.sys)
-	dumpint(memstats.nlookup)
-	dumpint(memstats.nmalloc)
-	dumpint(memstats.nfree)
-	dumpint(memstats.heap_alloc)
-	dumpint(memstats.heap_sys)
-	dumpint(memstats.heap_idle)
-	dumpint(memstats.heap_inuse)
-	dumpint(memstats.heap_released)
-	dumpint(memstats.heap_objects)
-	dumpint(memstats.stacks_inuse)
-	dumpint(memstats.stacks_sys)
-	dumpint(memstats.mspan_inuse)
-	dumpint(memstats.mspan_sys)
-	dumpint(memstats.mcache_inuse)
-	dumpint(memstats.mcache_sys)
-	dumpint(memstats.buckhash_sys)
-	dumpint(memstats.gc_sys)
-	dumpint(memstats.other_sys)
-	dumpint(memstats.next_gc)
-	dumpint(memstats.last_gc_unix)
-	dumpint(memstats.pause_total_ns)
+	dumpint(m.Alloc)
+	dumpint(m.TotalAlloc)
+	dumpint(m.Sys)
+	dumpint(m.Lookups)
+	dumpint(m.Mallocs)
+	dumpint(m.Frees)
+	dumpint(m.HeapAlloc)
+	dumpint(m.HeapSys)
+	dumpint(m.HeapIdle)
+	dumpint(m.HeapInuse)
+	dumpint(m.HeapReleased)
+	dumpint(m.HeapObjects)
+	dumpint(m.StackInuse)
+	dumpint(m.StackSys)
+	dumpint(m.MSpanInuse)
+	dumpint(m.MSpanSys)
+	dumpint(m.MCacheInuse)
+	dumpint(m.MCacheSys)
+	dumpint(m.BuckHashSys)
+	dumpint(m.GCSys)
+	dumpint(m.OtherSys)
+	dumpint(m.NextGC)
+	dumpint(m.LastGC)
+	dumpint(m.PauseTotalNs)
 	for i := 0; i < 256; i++ {
-		dumpint(memstats.pause_ns[i])
+		dumpint(m.PauseNs[i])
 	}
-	dumpint(uint64(memstats.numgc))
+	dumpint(uint64(m.NumGC))
 }
 
 func dumpmemprof_callback(b *bucket, nstk uintptr, pstk *uintptr, size, allocs, frees uintptr) {
@@ -639,7 +654,7 @@ func dumpmemprof() {
 
 var dumphdr = []byte("go1.7 heap dump\n")
 
-func mdump() {
+func mdump(m *MemStats) {
 	// make sure we're done sweeping
 	for _, s := range mheap_.allspans {
 		if s.state.get() == mSpanInUse {
@@ -654,13 +669,13 @@ func mdump() {
 	dumpgs()
 	dumpms()
 	dumproots()
-	dumpmemstats()
+	dumpmemstats(m)
 	dumpmemprof()
 	dumpint(tagEOF)
 	flush()
 }
 
-func writeheapdump_m(fd uintptr) {
+func writeheapdump_m(fd uintptr, m *MemStats) {
 	_g_ := getg()
 	casgstatus(_g_.m.curg, _Grunning, _Gwaiting)
 	_g_.waitreason = waitReasonDumpingHeap
@@ -674,7 +689,7 @@ func writeheapdump_m(fd uintptr) {
 	dumpfd = fd
 
 	// Call dump routine.
-	mdump()
+	mdump(m)
 
 	// Reset dump file.
 	dumpfd = 0