runtime: wait to update arena_used until after mapping bitmap
This avoids a race with gcmarkwb_m that was leading to faults.
Fixes #10212.
Change-Id: I6fcf8d09f2692227063ce29152cb57366ea22487
Reviewed-on: https://go-review.googlesource.com/10816
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index 2d7e556..d182ed6 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -418,9 +418,9 @@
// Keep taking from our reservation.
p := h.arena_used
sysMap((unsafe.Pointer)(p), n, h.arena_reserved, &memstats.heap_sys)
- h.arena_used += n
- mHeap_MapBits(h)
- mHeap_MapSpans(h)
+ mHeap_MapBits(h, p+n)
+ mHeap_MapSpans(h, p+n)
+ h.arena_used = p+n
if raceenabled {
racemapshadow((unsafe.Pointer)(p), n)
}
@@ -454,12 +454,12 @@
p_end := p + p_size
p += -p & (_PageSize - 1)
if uintptr(p)+n > uintptr(h.arena_used) {
- h.arena_used = p + n
+ mHeap_MapBits(h, p+n)
+ mHeap_MapSpans(h, p+n)
+ h.arena_used = p+n
if p_end > h.arena_end {
h.arena_end = p_end
}
- mHeap_MapBits(h)
- mHeap_MapSpans(h)
if raceenabled {
racemapshadow((unsafe.Pointer)(p), n)
}
