commit cc8f5441980a8c2f9e6c8ec3222985ed488e76ba [browse]
Author: Austin Clements
Date: 2015-07-16 16:27:09 -04:00

runtime: don't free large spans until heapBitsSweepSpan returns

This fixes a race between 1) sweeping and freeing an unmarked large
span and 2) reusing that span and allocating from it. This race arises
because mSpan_Sweep returns spans for large objects to the heap
*before* heapBitsSweepSpan clears the mark bit on the object in the
span.

Specifically, the following sequence of events can lead to an
incorrectly zeroed bitmap byte, which causes the garbage collector to
not trace any pointers in that object (the pointer bits for the first
four words are cleared, and the scan bits are also cleared, so it
looks like a no-scan object).

1) P0 calls mSpan_Sweep on a large span S0 with an unmarked object on it.

2) mSpan_Sweep calls heapBitsSweepSpan, which invokes the callback for
   the one (unmarked) object on the span.

3) The callback calls mHeap_Free, which makes span S0 available for
   allocation, but this is too early.

4) P1 grabs this S0 from the heap to use for allocation.

5) P1 allocates an object on this span and writes that object's type
   bits to the bitmap.

6) P0 returns from the callback to heapBitsSweepSpan.
   heapBitsSweepSpan clears the byte containing the mark, even though
   this span is now owned by P1 and this byte contains important
   bitmap information.

This fixes this problem by simply delaying the mHeap_Free until after
the heapBitsSweepSpan. I think the overall logic of mSpan_Sweep could
be simplified now, but this seems like the minimal change.

Fixes #11617.

Change-Id: I6b1382c7e7cc35f81984467c0772fe9848b7522a
Reviewed-on: https://go-review.googlesource.com/12320
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Rob Pike <r@golang.org>

commit 5c62e5f9da1fa0b16fa8da918b8fd1eb807b38c1 [browse]
Author: Rob Pike
Date: 2015-07-16 13:47:01 +10:00

cmd/fix: add gotypes module

Adjusts for the move from golang.org/x/tools/go/types and .../go/exact
to go/types and go/constant in the main repository.

Change-Id: I0da7248c540939e3e9b09c915b0a296937f1be73
Reviewed-on: https://go-review.googlesource.com/12284
Reviewed-by: Andrew Gerrand <adg@golang.org>

commit 29ffa4bd921125b73b04078fd293ecc4bdb9d7cd [browse]
Author: Mikio Hara
Date: 2015-07-16 15:41:34 +09:00

cmd/go: don't put mycmd in wrong directory

Change-Id: Ia7cc1d52211b32a2eb2b3888d621b28d6932aca9
Reviewed-on: https://go-review.googlesource.com/12290
Reviewed-by: Ian Lance Taylor <iant@golang.org>

commit 9f70cd8223fd1570075a888e596759774c0cb66d [browse]
Author: Carlos C
Date: 2015-07-09 15:08:39 +02:00

net/mail: add example to package

Change-Id: I912cafc66463f81cde839afc8f06b7eadcbf6f57
Reviewed-on: https://go-review.googlesource.com/11992
Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

commit f04c506917c585521e3ebbedd9ad2c0bc3c4fba5 [browse]
Author: Brad Fitzpatrick
Date: 2015-07-16 14:40:35 -07:00

A+C: more updates

Update #10639

Change-Id: I2d7817ac0aefb5dd2569d7e83afbc51851e24b42
Reviewed-on: https://go-review.googlesource.com/12321
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>