[dev.typealias] all: merge go1.8.3 into dev.typealiasdev.typealias

352996a381 (tag: go1.8.3) [release-branch.go1.8] go1.8.3
bb5055d6f1 [release-branch.go1.8] doc: document go1.8.3
439c0c8be8 [release-branch.go1.8] cmd/compile: don't move spills to loop exits where the spill is dead
e396667ba3 [release-branch.go1.8] cmd/compile: zero ambiguously live variables at VARKILLs
daf6706f37 [release-branch.go1.8] runtime: use pselect6 for usleep on linux/386
958c64bbab [release-branch.go1.8] runtime: use pselect6 for usleep on linux/amd64 and linux/arm
195e20a976 [release-branch.go1.8] cmd/compile: ignore types when considering tuple select for CSE
f55bc1c4eb [release-branch.go1.8] net/http: update bundled http2 for gracefulShutdownCh lock contention slowdown
51f508bb4a [release-branch.go1.8] cmd/compile: fix s390x unsigned comparison constant merging rules
243dee1737 [release-branch.go1.8] cmd/go: if we get a C compiler dwarf2 warning, try without -g
a43c0d2dc8 [release-branch.go1.8] runtime: don't corrupt arena bounds on low mmap
1054085dcf [release-branch.go1.8] cmd/compile: fix store chain in schedule pass
18a13d373a [release-branch.go1.8] runtime: doubly fix "double wakeup" panic
6efa2f22ac [release-branch.go1.8] database/sql: ensure releaseConn is defined before a possible close
fb9770f09b [release-branch.go1.8] runtime: print debug info on "base out of range"
b6a8fc8d8c [release-branch.go1.8] doc: remove mentions of yacc tool
59870f9e19 (tag: go1.8.2) [release-branch.go1.8] go1.8.2
c9688ddb6b [release-branch.go1.8] doc: document go1.8.2 and go1.7.6
38d35f49e7 [release-branch.go1.8] crypto/elliptic: fix carry bug in x86-64 P-256 implementation.

Change-Id: I2aa0eab7a990d24e25809fb13ce6cb031104f474

1 files changed, 13 insertions, 1 deletions

diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index da39dac510..6f07731a49 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -400,10 +400,12 @@ func (h *mheap) sysAlloc(n uintptr) unsafe.Pointer {
 			if p == 0 {
 				return nil
 			}
+			// p can be just about anywhere in the address
+			// space, including before arena_end.
 			if p == h.arena_end {
 				h.arena_end = new_end
 				h.arena_reserved = reserved
-			} else if h.arena_start <= p && p+p_size-h.arena_start-1 <= _MaxArena32 {
+			} else if h.arena_end < p && p+p_size-h.arena_start-1 <= _MaxArena32 {
 				// Keep everything page-aligned.
 				// Our pages are bigger than hardware pages.
 				h.arena_end = p + p_size
@@ -413,6 +415,16 @@ func (h *mheap) sysAlloc(n uintptr) unsafe.Pointer {
 				h.arena_used = used
 				h.arena_reserved = reserved
 			} else {
+				// We got a mapping, but it's not
+				// linear with our current arena, so
+				// we can't use it.
+				//
+				// TODO: Make it possible to allocate
+				// from this. We can't decrease
+				// arena_used, but we could introduce
+				// a new variable for the current
+				// allocation position.
+
 				// We haven't added this allocation to
 				// the stats, so subtract it from a
 				// fake stat (but avoid underflow).