1. The implementation uses distributed hash table of waitlists instead of a centralized one.
  It significantly improves scalability for uncontended semaphores.
2. The implementation provides wait-free fast-path for signalers.
3. The implementation uses less locks (1 lock/unlock instead of 5 for Semacquire).
4. runtime·ready() call is moved out of critical section.
5. Semacquire() does not call semwake().
Benchmark results on HP Z600 (2 x Xeon E5620, 8 HT cores, 2.40GHz)
are as follows:
benchmark                                        old ns/op    new ns/op    delta
runtime_test.BenchmarkSemaUncontended                58.20        36.30  -37.63%
runtime_test.BenchmarkSemaUncontended-2             199.00        18.30  -90.80%
runtime_test.BenchmarkSemaUncontended-4             327.00         9.20  -97.19%
runtime_test.BenchmarkSemaUncontended-8             491.00         5.32  -98.92%
runtime_test.BenchmarkSemaUncontended-16            946.00         4.18  -99.56%

runtime_test.BenchmarkSemaSyntNonblock               59.00        36.80  -37.63%
runtime_test.BenchmarkSemaSyntNonblock-2            167.00       138.00  -17.37%
runtime_test.BenchmarkSemaSyntNonblock-4            333.00       129.00  -61.26%
runtime_test.BenchmarkSemaSyntNonblock-8            464.00       130.00  -71.98%
runtime_test.BenchmarkSemaSyntNonblock-16          1015.00       136.00  -86.60%

runtime_test.BenchmarkSemaSyntBlock                  58.80        36.70  -37.59%
runtime_test.BenchmarkSemaSyntBlock-2               294.00       149.00  -49.32%
runtime_test.BenchmarkSemaSyntBlock-4               333.00       177.00  -46.85%
runtime_test.BenchmarkSemaSyntBlock-8               471.00       221.00  -53.08%
runtime_test.BenchmarkSemaSyntBlock-16              990.00       227.00  -77.07%

runtime_test.BenchmarkSemaWorkNonblock              829.00       832.00   +0.36%
runtime_test.BenchmarkSemaWorkNonblock-2            425.00       419.00   -1.41%
runtime_test.BenchmarkSemaWorkNonblock-4            308.00       220.00  -28.57%
runtime_test.BenchmarkSemaWorkNonblock-8            394.00       147.00  -62.69%
runtime_test.BenchmarkSemaWorkNonblock-16          1510.00       149.00  -90.13%

runtime_test.BenchmarkSemaWorkBlock                 828.00       813.00   -1.81%
runtime_test.BenchmarkSemaWorkBlock-2               428.00       436.00   +1.87%
runtime_test.BenchmarkSemaWorkBlock-4               232.00       219.00   -5.60%
runtime_test.BenchmarkSemaWorkBlock-8               392.00       251.00  -35.97%
runtime_test.BenchmarkSemaWorkBlock-16             1524.00       298.00  -80.45%

sync_test.BenchmarkMutexUncontended                  24.10        24.00   -0.41%
sync_test.BenchmarkMutexUncontended-2                12.00        12.00   +0.00%
sync_test.BenchmarkMutexUncontended-4                 6.25         6.17   -1.28%
sync_test.BenchmarkMutexUncontended-8                 3.43         3.34   -2.62%
sync_test.BenchmarkMutexUncontended-16                2.34         2.32   -0.85%

sync_test.BenchmarkMutex                             24.70        24.70   +0.00%
sync_test.BenchmarkMutex-2                          208.00        99.50  -52.16%
sync_test.BenchmarkMutex-4                         2744.00       256.00  -90.67%
sync_test.BenchmarkMutex-8                         5137.00       556.00  -89.18%
sync_test.BenchmarkMutex-16                        5368.00      1284.00  -76.08%

sync_test.BenchmarkMutexSlack                        24.70        25.00   +1.21%
sync_test.BenchmarkMutexSlack-2                    1094.00       186.00  -83.00%
sync_test.BenchmarkMutexSlack-4                    3430.00       402.00  -88.28%
sync_test.BenchmarkMutexSlack-8                    5051.00      1066.00  -78.90%
sync_test.BenchmarkMutexSlack-16                   6806.00      1363.00  -79.97%

sync_test.BenchmarkMutexWork                        793.00       792.00   -0.13%
sync_test.BenchmarkMutexWork-2                      398.00       398.00   +0.00%
sync_test.BenchmarkMutexWork-4                     1441.00       308.00  -78.63%
sync_test.BenchmarkMutexWork-8                     8532.00       847.00  -90.07%
sync_test.BenchmarkMutexWork-16                    8225.00      2760.00  -66.44%

sync_test.BenchmarkMutexWorkSlack                   793.00       793.00   +0.00%
sync_test.BenchmarkMutexWorkSlack-2                 418.00       414.00   -0.96%
sync_test.BenchmarkMutexWorkSlack-4                4481.00       480.00  -89.29%
sync_test.BenchmarkMutexWorkSlack-8                6317.00      1598.00  -74.70%
sync_test.BenchmarkMutexWorkSlack-16               9111.00      3038.00  -66.66%

R=rsc
CC=golang-dev
https://golang.org/cl/4631059

The public godoc looked confused. I imagine these were
written before current conventions were established.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4662060

R=rsc, iant, dvyukov
CC=golang-dev
https://golang.org/cl/4643057

R=rsc
CC=golang-dev
https://golang.org/cl/4625065

The implementation does not grab the lock,
if Once is already initalized.
Benchmark results on HP Z600 (2 x Xeon E5620, 8 HT cores, 2.40GHz)
are as follows:
benchmark                                        old ns/op    new ns/op    delta
sync_test.BenchmarkOnce                             187.00        14.00  -92.51%
sync_test.BenchmarkOnce-2                           909.00        21.40  -97.65%
sync_test.BenchmarkOnce-4                          3684.00        20.90  -99.43%
sync_test.BenchmarkOnce-8                          5987.00        23.00  -99.62%
sync_test.BenchmarkOnce-16                         5051.00        21.60  -99.57%

R=bradfitz, rsc
CC=golang-dev
https://golang.org/cl/4641066

including evaluation up the data tree (in this code all fields must be
in dot itself), plus more control structure, but the basics are in place.

R=rsc, r
CC=golang-dev
https://golang.org/cl/4665041

For both contended and uncontended case:
 - support arbitrary number of cpus (not just 2)
 - dynamic load balancing (improves stability)
 - periodic execution of Gosched() to work around non-preemptiviness
For uncontended case eliminates possible false-sharing.
For contended case includes additional variation with some
amount of local work between mutex operations.

R=r, rsc
CC=golang-dev
https://golang.org/cl/4634093

This avoids allocation when writing to bytes.Buffers and bufio.Writers, for
example.

R=golang-dev, rsc, r, consalus, r
CC=golang-dev
https://golang.org/cl/4625068

R=golang-dev, gri, bradfitz
CC=golang-dev
https://golang.org/cl/4634050

Against the spec, but appear in the wild.

Fixes #1966

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/4662059

Also fix \x{123} parsing.

R=r
CC=golang-dev
https://golang.org/cl/4632052

R=rsc
CC=golang-dev, vcc.163
https://golang.org/cl/4627071

#pragma varargck countpos f 1
says that the first argument to f is
the count of variadic arguments that follow.

#pragma varargck type f t
says that t is one of the allowed types for
a variadic argument to f.
(can be repeated)

combined, these can be used to check the
runtime.stdcall functions in the windows port
or in any other port that needs a vararg list of
uintptrs even on a 64-bit platform (where it is
very easy to pass a less-than-uintptr in the ...).

demo:

typedef unsigned int uintptr;

#pragma varargck countpos f 1
#pragma varargck type f uintptr
#pragma varargck type f void*

int f(int count, ...);

void *v;
char *p;

void
main(void)
{
        f(1, v);  // ok
        f(1, main);  // ok
        f(1, p);  // ok
        f(2, v, v);  // ok

        f(2, v);  // found 1 argument after count 2
        f(1, 'a');  // invalid type INT in call to f
        f(1, 0);  // invalid type INT in call to f
}

R=ken, r, alex.brainman
CC=golang-dev
https://golang.org/cl/4634103

It was working too hard.

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/4639081

R=r, sam.thorogood, kevlar
CC=golang-dev, rsc
https://golang.org/cl/4636046

Change the signature of Split to have no count,
assuming a full split, and rename the existing
Split with a count to SplitN.
Do the same to package bytes.
Add a gofix module.

R=adg, dsymonds, alex.brainman, rsc
CC=golang-dev
https://golang.org/cl/4661051

These are the relevant changes to exec_unix.go now that
mkerrors.sh outputs have been updated.

R=rsc
CC=golang-dev
https://golang.org/cl/4648064

I have written up a Marshal and MarshalIndent pair that should
closely reflect the way that Unmarshal works.  I would love feedback
on making this code more accessible and efficient... I haven't used
reflecton on this scale before, so there is probably a lot of work
that can be done on that.

Some potentially controversial things:
- All tag names are lower-cased by default.
- Zero-valued struct values are skipped.
- No namespace prefix (o:tag, etc) mechanism is supplied.
- You are allowed to marshal non-struct values (even though unmarshal
  cannot handle them).
- A tag for a non-XMLName struct field that isn't "attr", "chardata",
  or "innerxml" is used as the name of the tag.  This could wreak
  havoc if you try to marshal a protobuf struct.
- The "innerxml" and "chardata" are inserted verbatim.  If you try to
  marshal something straight from unmarshal, the results could be
  unexpected (remove "innerxml" support from Marshal would be one
  possible solution).

R=rsc
CC=golang-dev
https://golang.org/cl/4539082

R=golang-dev, bradfitz, r
CC=golang-dev
https://golang.org/cl/4634101

Fixes #2011

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4667043

R=dvyukov, r
CC=golang-dev
https://golang.org/cl/4657053

Fixes #2006.

R=ken2
CC=golang-dev
https://golang.org/cl/4643056

Permits serving from virtual filesystems, such as files linked
into a binary, or from a zip file.

Also adds a gofix for:

http.FileServer(root, prefix) -> http.StripPrefix(prefix, http.FileServer(http.Dir(root)))

R=r, rsc, gri, adg, dsymonds, r, gri
CC=golang-dev
https://golang.org/cl/4629047

Reader previously had cached an error from the underlying reader
and would return it on every subsequent call to Read.  The Reader
will now return the error only once, and subsequent calls will result
in a new Read call to the underlying Reader.

Fixes #1934.

R=bradfitz, rogpeppe, rsc
CC=golang-dev
https://golang.org/cl/4528133

R=r, rsc
CC=golang-dev
https://golang.org/cl/4650054

8a/a.h:
. Removed <u.h> and <libc.h> includes as they work better in "a.y".
. Made definition of EOF conditional as it's defined in the Plan 9
  header files, but not elsewhere.

8a/a.y:
. Added <u.h> and <libc.h> because <stdio.h> in Plan 9 needs them.
  Sequence <u.h>, <stdio.h>, <libc.h> recommended by RSC.

8a/lex.c:
. Added <u.h> and <libc.h> as now needed by "a.h".
. Dropped <ctype.h>.

cc/lexbody:
. exit() -> exits().
. Dropped unwanted incrementation.

cc/macbody:
. Adjusted a few format specifications.

R=rsc
CC=golang-dev
https://golang.org/cl/4644047

R=rsc, n13m3y3r, gustavo
CC=golang-dev
https://golang.org/cl/4661050

R=golang-dev, bradfitz, go.peter.90
CC=golang-dev
https://golang.org/cl/4627068

R=rsc
CC=golang-dev
https://golang.org/cl/4626067

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/4627067

Previously we were snapshotting the TLS state into *Request
before we did the HTTP ReadRequest, the first Read of which
triggered the TLS handshake implicitly.

Fixes #1956

R=golang-dev, rsc
CC=agl, golang-dev
https://golang.org/cl/4630072

-test.benchtime allows to specify benchmark execution time.
-test.cpu allows to execute tests/benchmarks for several
values of GOMAXPROCS.

R=r, r, rsc
CC=golang-dev
https://golang.org/cl/4662046

build runs with chmod 0 /bin/ed now

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/4635071

did darwin on mac with older, not broken xcode.
did linux arm by copying diffs from linux 386.
did freebsd amd64 by copying diffs from freebsd 386.

R=golang-dev, r, mikioh.mikioh
CC=golang-dev
https://golang.org/cl/4629067

Documentation mentioned the obsolete package "crypto/block",
which has been replaced with "crypto/cipher".

R=golang-dev, agl
CC=golang-dev
https://golang.org/cl/4654064

Fixes #1970.

R=rsc, r
CC=golang-dev
https://golang.org/cl/4650050

Fixes #1969.

R=gri, rsc, r
CC=golang-dev
https://golang.org/cl/4634076

- don't rely on /dev/stdin as the name for standard input
- employ EBNF extraction if the source contains tags

"cat source.html | ebnflint" works now

R=r
CC=golang-dev
https://golang.org/cl/4641075

Users of the Scan() infrastructure that employ ReadRune() rather than
Token() need a way to skip leading spaces and newlines as set by the
the parent, Fscan(), Fscanln, or Fscanf(). As the internal methods and
boolean flags are not exported, this new function was added here and
in the Int and Nat Scan() functions of the big package. (fmt.Rat did
not need change since it uses Token()) Also added Printf style format
code support to int types and tests for same to int_test.go

R=r, r, gri, mtj
CC=golang-dev
https://golang.org/cl/4634074

As rsc suggested after change 58a6bdac3d12 was committed, we
now read the first byte of Request.Body when the
Request.ContentLength is 0 to disambiguate between a truly
zero-length body and a body of unknown length where the user
didn't set the ContentLength field.

This was also causing the reverse proxy problem where incoming
requests (which always have a body, of private type http.body,
even for 0-lengthed requests) were being relayed to the http
Transport for fetching, which was serializing the request as a
chunked request (since ContentLength was 0 and Body was
non-nil)

Fixes #1999

R=golang-dev, kevlar
CC=golang-dev
https://golang.org/cl/4628063