runtime: improve block profiler support for channels
1. Handle select statements.
2. Handle chan close.
3. Show top frame in debug mode (chansend/chanrecv/selectgo).
Fixes issue 6049.

R=golang-dev, daniel.morsing, rsc
CC=golang-dev
https://codereview.appspot.com/12694050
Merge branch 'master' into gitfix
runtime.cmd/ld: Add ARM external linking and implement -shared in terms of external linking

This CL is an aggregate of 10271047, 10499043, 9733044. Descriptions of each follow:

10499043
runtime,cmd/ld: Merge TLS symbols and teach 5l about ARM TLS

This CL prepares for external linking support to ARM.

The pseudo-symbols runtime.g and runtime.m are merged into a single
runtime.tlsgm symbol. When external linking, the offset of a thread local
variable is stored at a memory location instead of being embedded into a offset
of a ldr instruction. With a single runtime.tlsgm symbol for both g and m, only
one such offset is needed.

The larger part of this CL moves TLS code from gcc compiled to internally
compiled. The TLS code now uses the modern MRC instruction, and 5l is taught
about TLS fallbacks in case the instruction is not available or appropriate.

10271047
This CL adds support for -linkmode external to 5l.

For 5l itself, use addrel to allow for D_CALL relocations to be handled by the
host linker. Of the cases listed in rsc's comment in issue 4069, only case 5 and
63 needed an update. One of the TODO: addrel cases was since replaced, and the
rest of the cases are either covered by indirection through addpool (cases with
LTO or LFROM flags) or stubs (case 74). The addpool cases are covered because
addpool emits AWORD instructions, which in turn are handled by case 11.

In the runtime, change the argv argument in the rt0* functions slightly to be a
pointer to the argv list, instead of relying on a particular location of argv.

9733044
The -shared flag to 6l outputs a shared library, implemented in Go
and callable from non-Go programs such as C.

The main part of this CL change the thread local storage model.
Go uses the fastest and least general mode, local exec. TLS data in shared
libraries normally requires at least the local dynamic mode, however, this CL
instead opts for using the initial exec mode. Initial exec mode is faster than
local dynamic mode and can be used in linux since the linker has reserved a
limited amount of TLS space for performance sensitive TLS code.

Initial exec mode requires an extra load from the GOT table to determine the
TLS offset. This penalty will not be paid if ld is not in -shared mode, since
TLS accesses will be reduced to local exec.

The elf sections .init_array and .rela.init_array are added to register the Go
runtime entry with cgo at library load time.

The "hidden" attribute is added to Cgo functions called from Go, since Go
does not generate call through the GOT table, and adding non-GOT relocations for
a global function is not supported by gcc. Cgo symbols don't need to be global
and avoiding the GOT table is also faster.

The changes to 8l are only removes code relevant to the old -shared mode where
internal linking was used.

This CL only address the low level linker work. It can be submitted by itself,
but to be useful, the runtime changes in CL 9738047 is also needed.

Design discussion at
https://groups.google.com/forum/?fromgroups#!topic/golang-nuts/zmjXkGrEx6Q

Fixes issue 5590.

R=rsc
CC=golang-dev
https://codereview.appspot.com/12871044

Committer: Russ Cox <rsc@golang.org>
A+C: Matt Joiner (individual CLA)

Generated by addca.

R=gobot
CC=golang-dev
https://codereview.appspot.com/12933043
database/sql: fix accumulation of bad conns on prepared statements

Fixes an issue where prepared statements that outlive many
connections become expensive to invoke.

Fixes issue 6081

R=golang-dev
CC=bradfitz, golang-dev
https://codereview.appspot.com/12646044

Committer: Brad Fitzpatrick <bradfitz@golang.org>
cmd/cgo: fix windows build

        The shared library changes broke the windows build because __attribute__ ((visibility ("hidden"))) is not supported in windows gcc. This change removes the attribute, as it is only needed when building shared libraries.

R=rsc
CC=golang-dev
https://codereview.appspot.com/12829044

Committer: Russ Cox <rsc@golang.org>
cmd/dist: fix darwin build

The TLS block on Darwin is not the same as on ELF.

TBR=elias.naur
CC=golang-dev
https://codereview.appspot.com/12741044
runtime: Fix netbsd/arm and freebsd/arm build

        The ARM external linking CL left missed changes to sys_freebsd_arm.s and sys_netbsd_arm.s already done to sys_linux_arm.s.

R=rsc
CC=golang-dev
https://codereview.appspot.com/12842044

Committer: Russ Cox <rsc@golang.org>
net: make TestDeadlineRace shorter
1. Do less iterations in short mode
2. Bound number of times SetDeadline is executed

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/12937043
runtime: Fix build on older ARM

        The ARM external linking CL used BLX instructions in gcc assembler. Replace with BL to retain support on older ARM processors.

R=rsc
CC=golang-dev
https://codereview.appspot.com/12938043

Committer: Russ Cox <rsc@golang.org>
net: make TCPStress test shorter
It timeouts on freebsd builders:
http://build.golang.org/log/3d8169e13bff912bebf6fd3c54b34ad2d29a7221
but there are always runnable goroutines,
which suggests that it's slowly progressing.

R=golang-dev, bradfitz
CC=golang-dev
https://codereview.appspot.com/12939043
runtime: implement SysUnused on windows
Fixes issue 5584.

R=golang-dev, chaishushan, alex.brainman
CC=golang-dev
https://codereview.appspot.com/12720043
Merge branch 'master' into gitfix
runtime: fix windows build

R=golang-dev
CC=golang-dev
https://codereview.appspot.com/12941043
runtime/cgo: use old-style indirect call on arm

TBR=elias.naur
CC=golang-dev
https://codereview.appspot.com/12943043
runtime: make SetFinalizer(x, f) accept any f for which f(x) is valid

Originally the requirement was f(x) where f's argument is
exactly x's type.

CL 11858043 relaxed the requirement in a non-standard
way: f's argument must be exactly x's type or interface{}.

If we're going to relax the requirement, it should be done
in a way consistent with the rest of Go. This CL allows f's
argument to have any type for which x is assignable;
that's the same requirement the compiler would impose
if compiling f(x) directly.

Fixes issue 5368.

R=dvyukov, bradfitz, pieter
CC=golang-dev
https://codereview.appspot.com/12895043
encoding/json: support encoding.TextMarshaler, encoding.TextUnmarshaler

R=golang-dev, bradfitz
CC=golang-dev
https://codereview.appspot.com/12703043
encoding/xml: add, support Unmarshaler interface

See golang.org/s/go12xml for design.

R=golang-dev, dominik.honnef, dan.kortschak
CC=golang-dev
https://codereview.appspot.com/12556043
encoding/xml: add, support Marshaler interface

See golang.org/s/go12xml for design.

Repeat of CL 12603044, which was submitted accidentally
and then rolled back.

Fixes issue 2771.
Fixes issue 4169.
Fixes issue 5975.
Fixes issue 6125.

R=golang-dev
CC=golang-dev
https://codereview.appspot.com/12919043
cmd/5g, cmd/6g, cmd/8g: restore occurrences of R replaced by nil in comments.

R=golang-dev, bradfitz, rsc
CC=golang-dev
https://codereview.appspot.com/12842043