From f65bb028c5ceb4fb213b103f24a85f17cf67ac39 Mon Sep 17 00:00:00 2001 From: Russ Cox Date: Thu, 30 Oct 2014 10:16:03 -0400 Subject: [dev.garbage] cmd/gc, runtime: implement write barriers in terms of writebarrierptr This CL implements the many multiword write barriers by calling writebarrierptr, so that only writebarrierptr needs the actual barrier. In lieu of an actual barrier, writebarrierptr checks that the value being copied is not a small non-zero integer. This is enough to shake out bugs where the barrier is being called when it should not (for non-pointer values). It also found a few tests in sync/atomic that were being too clever. This CL adds a write barrier for the memory moved during the builtin copy function, which I forgot when inserting barriers for Go 1.4. This CL re-enables some write barriers that were disabled for Go 1.4. Those were disabled because it is possible to change the generated code so that they are unnecessary most of the time, but we have not changed the generated code yet. For safety they must be enabled. None of this is terribly efficient. We are aiming for correct first. LGTM=rlh R=rlh CC=golang-codereviews https://codereview.appspot.com/168770043 --- src/sync/atomic/atomic_test.go | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'src/sync') diff --git a/src/sync/atomic/atomic_test.go b/src/sync/atomic/atomic_test.go index 9f13af48b..ec573aa8c 100644 --- a/src/sync/atomic/atomic_test.go +++ b/src/sync/atomic/atomic_test.go @@ -164,7 +164,7 @@ func TestSwapPointer(t *testing.T) { x.before = magicptr x.after = magicptr var j uintptr - for delta := uintptr(1); delta+delta > delta; delta += delta { + for delta := uintptr(1 << 16); delta+delta > delta; delta += delta { k := SwapPointer(&x.i, unsafe.Pointer(delta)) if uintptr(x.i) != delta || uintptr(k) != j { t.Fatalf("delta=%d i=%d j=%d k=%d", delta, x.i, j, k) @@ -456,7 +456,7 @@ func TestCompareAndSwapPointer(t *testing.T) { magicptr := uintptr(m) x.before = magicptr x.after = magicptr - for val := uintptr(1); val+val > val; val += val { + for val := uintptr(1 << 16); val+val > val; val += val { x.i = unsafe.Pointer(val) if !CompareAndSwapPointer(&x.i, unsafe.Pointer(val), unsafe.Pointer(val+1)) { t.Fatalf("should have swapped %#x %#x", val, val+1) @@ -595,7 +595,7 @@ func TestLoadPointer(t *testing.T) { magicptr := uintptr(m) x.before = magicptr x.after = magicptr - for delta := uintptr(1); delta+delta > delta; delta += delta { + for delta := uintptr(1 << 16); delta+delta > delta; delta += delta { k := LoadPointer(&x.i) if k != x.i { t.Fatalf("delta=%d i=%d k=%d", delta, x.i, k) @@ -731,7 +731,7 @@ func TestStorePointer(t *testing.T) { x.before = magicptr x.after = magicptr v := unsafe.Pointer(uintptr(0)) - for delta := uintptr(1); delta+delta > delta; delta += delta { + for delta := uintptr(1 << 16); delta+delta > delta; delta += delta { StorePointer(&x.i, unsafe.Pointer(v)) if x.i != v { t.Fatalf("delta=%d i=%d v=%d", delta, x.i, v) -- cgit v1.2.1