This significantly decreases amount of shadow memory
mapped by race detector.
I haven't tested on Windows, but on Linux it reduces
virtual memory size from 1351m to 330m for fmt.test.
Fixes#4379.
R=golang-dev, alex.brainman, iant
CC=golang-dev
https://golang.org/cl/6849057
It allows to catch e.g. a data race between atomic write and non-atomic write,
or Mutex.Lock() and mutex overwrite (e.g. mu = Mutex{}).
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6817103
Currently race detector runtime maps shadow memory eagerly at process startup.
It works poorly on Windows, because Windows requires reservation in swap file
(especially problematic if several Go program runs at the same, each consuming GBs
of memory).
With this change race detector maps shadow memory lazily, so Go runtime must notify
about all new heap memory.
It will help with Windows port, but also eliminates scary 16TB virtual mememory
consumption in top output (which sometimes confuses some monitoring scripts).
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6811085
It speedups the race detector somewhat, but also prevents
getcallerpc() from obtaining lessstack().
R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/6812091