There are at least 3 bugs:
1. g->stacksize accounting is broken during copystack/shrinkstack
2. stktop->free is not properly maintained during copystack/shrinkstack
3. stktop->free logic is broken:
        we can have stktop->free==FixedStack,
        and we will free it into stack cache,
        but it actually comes from heap as the result of non-copying segment shrink
This shows as at least spurious races on race builders (maybe something else as well I don't know).

The idea behind the refactoring is to consolidate stacksize and
segment origin logic in stackalloc/stackfree.

Fixes #7490.

LGTM=rsc, khr
R=golang-codereviews, rsc, khr
CC=golang-codereviews
https://golang.org/cl/72440043

Recursive panics leave dangling Panic structs in g->panic stack.
At best it leads to a Defer leak and incorrect output on a subsequent panic.
At worst it arbitrary corrupts heap.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/72480043

One reason the sync.Pool finalizer test can fail is that
this function's ef1 contains uninitialized data that just
happens to point at some of the old pool. I've seen this cause
retention of a single pool cache line (32 elements) on arm.

Really we need liveness information for C functions, but
for now we can be more careful about data in long-lived
C functions that block.

LGTM=bradfitz, dvyukov
R=golang-codereviews, bradfitz, dvyukov
CC=golang-codereviews, iant, khr
https://golang.org/cl/72490043

Replaces CL 70000043.

Switch to the amd64p32 linker model if we are building under nacl/amd64p32.

No need to introduce linkarchinit() as 6a contains its own main() function.

LGTM=rsc
R=rsc, minux.ma
CC=golang-codereviews
https://golang.org/cl/72020043

Replaces CL 70000043.

Introduce linkarchinit() from cmd/ld.

For cmd/6g, switch to the amd64p32 linker model if we are building under nacl/amd64p32.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/71330045

Just commentary describing existing behavior, no code changes.

Fixes #7033.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71860043

Documenting existing behavior; new commentary only.
Fixes #7105.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/68840044

This documents the status quo for most implementations,
with one exception: gc generates a run-time error for
constant but out-of-range indices when slicing a constant
string. See issue 7200 for a detailed discussion.

LGTM=r
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/72160044

Instead, split the underlying storage in half and
free just half of it.

Shrinking without copying lets us reclaim storage used
by a previously profligate Go routine that has now blocked
inside some C code.

To shrink in place, we need all stacks to be a power of 2 in size.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/69580044

This is a test case for CL 34680044.

Fixes #6333.

LGTM=bradfitz
R=golang-codereviews, bradfitz, minux.ma
CC=golang-codereviews
https://golang.org/cl/71230049

Two memory allocator bug fixes.

- efence is not maintaining the proper heap metadata
  to make eventual memory reuse safe, so use SysFault.

- now that our heap PageSize is 8k but most hardware
  uses 4k pages, SysAlloc and SysReserve results must be
  explicitly aligned. Do that in a few more call sites and
  document this fact in malloc.h.

Fixes #7448.

LGTM=iant
R=golang-codereviews, josharian, iant
CC=dvyukov, golang-codereviews
https://golang.org/cl/71750048

cmd/5c/txt.c was missing from CL 72010043.

LGTM=bradfitz
R=rsc, bradfitz
CC=golang-codereviews
https://golang.org/cl/72220043

Replaces CL 70000043.

Introduce linkarchinit() from cmd/ld.

For cmd/6c, switch to the amd64p32 linker model if we are building under nacl/amd64p32.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/72010043

I've just needed the G status on fault to debug runtime bug.
For some reason we print everything except header here.
Make it more informative and consistent.

R=rsc
CC=golang-codereviews
https://golang.org/cl/67870056

warning: pkg/runtime/mgc0.c:2352 format mismatch p UVLONG, arg 2
warning: pkg/runtime/mgc0.c:2352 format mismatch p UVLONG, arg 3

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71950044

Implement custom assembly thunks for hot race calls (memory accesses and function entry/exit).
The thunks extract caller pc, verify that the address is in heap or global and switch to g0 stack.

Before:
ok  	regexp	3.692s
ok  	compress/bzip2	9.461s
ok  	encoding/json	6.380s
After:
ok  	regexp	2.229s (-40%)
ok  	compress/bzip2	4.703s (-50%)
ok  	encoding/json	3.629s (-43%)

For comparison, normal non-race build:
ok  	regexp	0.348s
ok  	compress/bzip2	0.304s
ok  	encoding/json	0.661s
Race build:
ok  	regexp	2.229s (+540%)
ok  	compress/bzip2	4.703s (+1447%)
ok  	encoding/json	3.629s (+449%)

Also removes some race-related special cases from cgocall and scheduler.
In long-term it will allow to remove cyclic runtime/race dependency on cmd/cgo.

Fixes #4249.
Fixes #7460.
Update #6508
Update #6688

R=iant, rsc, bradfitz
CC=golang-codereviews
https://golang.org/cl/55100044

Fixes #7196

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews, iant
https://golang.org/cl/69970052

NOT A LANGUAGE CHANGE.

Fixes #7073.

LGTM=r
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/68840045

LGTM=khr
R=khr
CC=golang-codereviews, rsc
https://golang.org/cl/69870054

It was caused by mstats.heap_alloc skew.
Fixes #7430.

LGTM=khr
R=golang-codereviews, khr
CC=golang-codereviews, rsc
https://golang.org/cl/69870055

Currently it fails on second and subsequent runs (when using -cpu=1,2,4) as:
--- FAIL: TestUseProxy-4 (0.00 seconds)
proxy_test.go:109: useProxy(barbaz.net) = true, want false
proxy_test.go:109: useProxy(foobar.com) = true, want false
proxy_test.go:109: useProxy(www.foobar.com) = true, want false

LGTM=bradfitz
R=bradfitz
CC=golang-codereviews
https://golang.org/cl/71940044

Fixes #7459.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/71060044

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71950043

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71940043

Tested GOARM=6 on Raspberry Pi, and I found only a few tests that
use sub-normal numbers fails. I have a patch to NetBSD kernel pending
that fixes this issue (NetBSD kernel doesn't allow us to disable the
Flush-to-Zero feature).

LGTM=jsing
R=golang-codereviews, jsing
CC=golang-codereviews
https://golang.org/cl/70730043

LGTM=jsing
R=golang-codereviews, jsing
CC=golang-codereviews
https://golang.org/cl/70720043

The underlying type of the predeclared type error is not itself,
but the interface it is defined as.

Fixes #7444.

LGTM=r, rsc
R=r, rsc, iant, ken
CC=golang-codereviews
https://golang.org/cl/71790044

Fixes #7449.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71610044

To be enabled by https://golang.org/cl/71230045/

Update #7442

LGTM=adg
R=adg
CC=golang-codereviews
https://golang.org/cl/69860056

I missed this one in codereview.appspot.com/70010050
Same thing, but different test.

Fixes windows-amd64-race and likely other Windows
machines failing like:
http://build.golang.org/log/0382bf0048bf5835a51a8a902df5c6fc73cd7ff5

LGTM=adg
R=rsc, adg
CC=golang-codereviews
https://golang.org/cl/71770043

CLA links are now redirects. Use new URLs instead.

Also, use https:// links for all Google sites where
the http version just redirects to https anyway.
(That's all links on the page, as it turns out)

LGTM=adg
R=golang-codereviews, adg
CC=golang-codereviews
https://golang.org/cl/69980051

Also add it to doc/go1.3.txt.

Update #7289

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/71740043

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71670043

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71700043

Fixes #7289.

LGTM=bradfitz
R=golang-codereviews, r, bradfitz, rsc
CC=golang-codereviews
https://golang.org/cl/52660047

Generated by addca.

R=gobot
CC=golang-codereviews
https://golang.org/cl/71570044

Fixes the syscall test.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/71470043

This documents the implemented behavior of both
gc and gccgo as an implementation restriction.

NOT A LANGUAGE CHANGE.

Fixes #5425.

LGTM=rsc, r, iant
R=r, iant, rsc, ken
CC=golang-codereviews
https://golang.org/cl/71430043

Essentialy for running tests without a working cmd/go.
While we're at it, also fix a typo.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/70640043

During the glob decoding process interface values are set to concrete
values after a test for assignability. If the assignability test fails
a slightly vague error message is produced. While technically accurate
the error message does not clearly describe the problem.

Rewrite the error message to include the usage of the word assignable,
which makes it clear the concrete value type is not assignable to the
interface value type.

Fixes #6467.

LGTM=r
R=golang-codereviews, rsc, r
CC=golang-codereviews
https://golang.org/cl/71590043