If the stack frame size is larger than the known-unmapped region at the
bottom of the address space, then the stack split prologue cannot use the usual
condition:

        SP - size >= stackguard

because SP - size may wrap around to a very large number.
Instead, if the stack frame is large, the prologue tests:

        SP - stackguard >= size

(This ends up being a few instructions more expensive, so we don't do it always.)

Preemption requests register by setting stackguard to a very large value, so
that the first test (SP - size >= stackguard) cannot possibly succeed.
Unfortunately, that same very large value causes a wraparound in the
second test (SP - stackguard >= size), making it succeed incorrectly.

To avoid *that* wraparound, we have to amend the test:

        stackguard != StackPreempt && SP - stackguard >= size

This test is only used for functions with large frames, which essentially
always split the stack, so the cost of the few instructions is noise.

This CL and CL 11085043 together fix the known issues with preemption,
at the beginning of a function, so we will be able to try turning it on again.

R=ken2
CC=golang-dev
https://golang.org/cl/11205043

This is a transcript before this change. I've capitalized the text being removed.
Note that it is always near another line that already says fmt, marked with <<<

$ cd $GOROOT/src/pkg/fmt

$ go test -cover
PASS
coverage FOR FMT: 91.3% of statements
ok  	fmt	0.040s <<<

$ go test -coverpkg strconv
PASS
coverage FOR FMT: 64.9% of statements in strconv
ok  	fmt	0.039s <<<

$ go test -cover -c
$ ./fmt.test -test.covermode=set <<<
PASS
coverage FOR FMT: 91.3% of statements

$ go test -coverpkg strconv -c
$ ./fmt.test -test.covermode=set <<<
PASS
coverage FOR FMT: 64.9% of statements in strconv

That the summary printed by 'go test [options] fmt' is unchanged:

$ go test -cover fmt
ok  	fmt	0.040s	coverage: 91.3% of statements

$ go test -coverpkg strconv fmt
ok  	fmt	0.038s	coverage: 64.9% of statements in strconv

R=r
CC=gobot, golang-dev
https://golang.org/cl/10932045

Fixes build for some slow FreeBSD/NetBSD/Darwin builder.

R=golang-dev
CC=golang-dev
https://golang.org/cl/11207043

Missed this in CL 10909045.

TBR=golang-dev
CC=golang-dev
https://golang.org/cl/10803045

Fixes #5836.

R=golang-dev, bradfitz, r, rsc
CC=golang-dev
https://golang.org/cl/10883045

The current cas64 definition hard-codes the x86 behavior
of updating *old with the new value when the cas fails.
This is inconsistent with cas32 and casp.
Make it consistent.

This means that the cas64 uses will be epsilon less efficient
than they might be, because they have to do an unnecessary
memory load on x86. But so be it. Code clarity and consistency
is more important.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/10909045

I hate bash.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/11200043

The static func named thread in issue5337.go's C snippet
conflicts with the static func named thread in issue3350.go's C snippet.
I don't know why (they're both static) but I also don't care,
because -linkmode=internal only needs to be able to handle
the cgo in the standard library, and it does.

Change the test to avoid this problem.

Fixes build (after run.bash is fixed to detect the breakage).

R=minux.ma
TBR=minux.ma
CC=golang-dev
https://golang.org/cl/11201043

R=golang-dev, dave, r
CC=golang-dev, nigeltao
https://golang.org/cl/10713043

STRINGSZ (200) is fine for lines generated by things like
instruction dumps, but an error containing a couple file
names can easily exceed that, especially on Macs with
the ridiculous default $TMPDIR.

R=ken2
CC=golang-dev
https://golang.org/cl/11199043

Fixes #5853.

R=ken2
CC=golang-dev
https://golang.org/cl/11104044

The json package cheerfully would marshal

        type S struct {
                IP net.IP
        }

but would give an error when unmarshalling.  This change allows any
type whose concrete type is a byte slice to be unmarshalled from a
string.

Fixes #5086.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/11161044

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/11064044

when the program is not main package, `go run x.go` can't return the
link error message. so use `go run x.go` in instead `go build x.go`.

Fixes #5865.

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/11165043

Fixes #5862.

R=r
CC=golang-dev
https://golang.org/cl/11168043

R=golang-dev
CC=golang-dev
https://golang.org/cl/11188043

Fixes #3250.

R=rsc
CC=golang-dev
https://golang.org/cl/10757044

1. "int e;" is unused, generating "unused variable" error.
2. a->e was typed void *[2], but was accessed with *(int *)(a->e), this
generated "dereferencing type-punned pointer will break strict-aliasing rules" error.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/11009043

Update #5847
Summary: syscall: implement Sendfile for OpenBSD and NetBSD

R=golang-dev, rsc, dave
CC=golang-dev
https://golang.org/cl/10980043

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/10981043

runtime.newproc/ready are deliberately sloppy about waking new M's,
they only ensure that there is at least 1 spinning M.
Currently to compensate for that, schedule() checks if the current P
has local work and there are no spinning M's, it wakes up another one.
It does not work if goroutines do not call schedule.
With this change a spinning M wakes up another M when it finds work to do.
It's also not ideal, but it fixes the underutilization.
A proper check would require to know the exact number of runnable G's,
but it's too expensive to maintain.
Fixes #5586.
This is reincarnation of cl/9776044 with the bug fixed.
The bug was due to code added after cl/9776044 was created:
if(tick - (((uint64)tick*0x4325c53fu)>>36)*61 == 0 && runtime·sched.runqsize > 0) {
        runtime·lock(&runtime·sched);
        gp = globrunqget(m->p, 1);
        runtime·unlock(&runtime·sched);
}
If M gets gp from global runq here, it does not reset m->spinning.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/10743044

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/10855043

Currently it crashes as follows:
fatal error: unknown pc
...
goroutine 71698 [runnable]:
runtime.racegoend()
        src/pkg/runtime/race.c:171
runtime.goexit()
        src/pkg/runtime/proc.c:1276 +0x9
created by runtime_test.testConcurrentReadsAfterGrowth
        src/pkg/runtime/map_test.go:264 +0x332

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/10674047

R=r
CC=andybons, golang-dev
https://golang.org/cl/11148043

If you compute the size by subtraction from the address
of the next symbol, it helps to wait until the symbols have
been sorted by address.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/11143043

R=r, andybons
CC=andybons, golang-dev
https://golang.org/cl/10977043

R=khr
CC=golang-dev
https://golang.org/cl/11131043

Instead, rely on the type checker.

R=adonovan
CC=golang-dev
https://golang.org/cl/10826044

R=golang-dev, dsymonds, bradfitz
CC=golang-dev
https://golang.org/cl/11095043

Fixes #5783

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/10956043

The notion of a named type is crucial for the definition
of type identity, assignability, definitions of methods.
Explicitly introduce the notion with an extra sentence.

Fixes #5682.

R=r, rsc, iant
CC=golang-dev
https://golang.org/cl/11055043

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/11080043

Fixes #5843.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/11073043

Merging a couple of CLs into one, since they collided in my client
and I'm lazy.

1) Fix up output in "go test -cover" case.
We need to tell the testing package the name of the package being tested
and the name of the package being covered. It can then sort out the report.

2) Filter out the _test.go files from coverage processing. We want to measure
what the tests cover, not what's covered in the tests,
The coverage for encoding/gob goes from 82.2% to 88.4%.
There may be a cleaner way to do this - suggestions welcome - but ça suffit.

Fixes #5810.

R=rsc
CC=golang-dev
https://golang.org/cl/10868047

Fixes #5787.

R=r
CC=golang-dev
https://golang.org/cl/11057043

R=r, rsc, andybons
CC=andybons, golang-dev
https://golang.org/cl/10890045

Fix warning found by clang 3.3.

R=rsc, r
CC=golang-dev
https://golang.org/cl/11022043

R=r
CC=golang-dev
https://golang.org/cl/10758044

Fixes #5503.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/10989043

CL 10869046 changed cmd/go to checkout master branch, so
for "go get -u" to work, it must "git pull" instead of
"git fetch". Added "--ff-only" so that it won't accidentally
overwrite user changes.

R=dsymonds
CC=golang-dev
https://golang.org/cl/10907043