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Russ Cox e03dd07981 runtime: disable preemption during software fp routines
It's okay to preempt at ordinary function calls because
compilers arrange that there are no live registers to save
on entry to the function call.

The software floating point routines are function calls
masquerading as individual machine instructions. They are
expected to keep all the registers intact. In particular,
they are expected not to clobber all the floating point
registers.

The floating point registers are kept per-M, because they
are not live at non-preemptive goroutine scheduling events,
and so keeping them per-M reduces the number of 132-byte
register blocks we are keeping in memory.

Because they are per-M, allowing the goroutine to be
rescheduled during software floating point simulation
would mean some other goroutine could overwrite the registers
or perhaps the goroutine would continue running on a different
M entirely.

Disallow preemption during the software floating point
routines to make sure that a function full of floating point
instructions has the same floating point registers throughout
its execution.

R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/12298043
2013-08-01 20:07:01 -04:00
api api: update next.txt 2013-06-14 10:00:07 -07:00
doc doc: remove jquery.js and style.css 2013-08-01 17:36:45 +10:00
include include/plan9: define size_t to fix build breakage 2013-06-28 12:16:33 -07:00
lib cmd/godoc: delete from core repository 2013-08-01 11:21:17 +10:00
misc misc/dist: include godoc from go.tools 2013-08-01 16:48:31 +10:00
src runtime: disable preemption during software fp routines 2013-08-01 20:07:01 -04:00
test cmd/gc: insert \n at end of every input file 2013-07-30 10:27:08 -04:00
.hgignore hgignore: cleanup obsolete entries. 2013-06-02 11:36:09 +02:00
.hgtags tag go1.1.1 2013-06-13 12:52:02 +10:00
AUTHORS A+C: Scott Ferguson (individual CLA) 2013-08-01 15:49:35 -07:00
CONTRIBUTORS A+C: Scott Ferguson (individual CLA) 2013-08-01 15:49:35 -07:00
favicon.ico godoc: update favicon 2012-10-11 17:02:36 +11:00
LICENSE doc: update licensing text one more time 2012-03-27 15:09:13 +11:00
PATENTS LICENSE: separate, change PATENTS text 2010-12-06 16:31:59 -05:00
README build: update, streamline documentation for new $GOBIN 2010-08-24 20:00:50 -04:00
robots.txt godoc: serve robots.txt raw 2011-02-19 05:46:20 +11:00

This is the source code repository for the Go programming language.  

For documentation about how to install and use Go,
visit http://golang.org/ or load doc/install.html in your web browser.

After installing Go, you can view a nicely formatted
doc/install.html by running godoc --http=:6060
and then visiting http://localhost:6060/doc/install.html.

Unless otherwise noted, the Go source files are distributed
under the BSD-style license found in the LICENSE file.

--

Binary Distribution Notes

If you have just untarred a binary Go distribution, you need to set
the environment variable $GOROOT to the full path of the go
directory (the one containing this README).  You can omit the
variable if you unpack it into /usr/local/go, or if you rebuild
from sources by running all.bash (see doc/install.html).
You should also add the Go binary directory $GOROOT/bin
to your shell's path.

For example, if you extracted the tar file into $HOME/go, you might
put the following in your .profile:

    export GOROOT=$HOME/go
    export PATH=$PATH:$GOROOT/bin

See doc/install.html for more details.