Given:
p := alloc()
fn_taking_ptr(p)
p is NOT recorded as live at the call to fn_taking_ptr:
it's not needed by the code following the call.
p was passed to fn_taking_ptr, and fn_taking_ptr must keep
it alive as long as it needs it.
In practice, fn_taking_ptr will keep its own arguments live
for as long as the function is executing.
But if instead you have:
p := alloc()
i := uintptr(unsafe.Pointer(p))
fn_taking_int(i)
p is STILL NOT recorded as live at the call to fn_taking_int:
it's not needed by the code following the call.
fn_taking_int is responsible for keeping its own arguments
live, but fn_taking_int is written to take an integer, so even
though fn_taking_int does keep its argument live, that argument
does not keep the allocated memory live, because the garbage
collector does not dereference integers.
The shorter form:
p := alloc()
fn_taking_int(uintptr(unsafe.Pointer(p)))
and the even shorter form:
fn_taking_int(uintptr(unsafe.Pointer(alloc())))
are both the same as the 3-line form above.
syscall.Syscall is like fn_taking_int: it is written to take a list
of integers, and yet those integers are sometimes pointers.
If there is no other copy of those pointers being kept live,
the memory they point at may be garbage collected during
the call to syscall.Syscall.
This is happening on Solaris: for whatever reason, the timing
is such that the garbage collector manages to free the string
argument to the open(2) system call before the system call
has been invoked.
Change the system call wrappers to insert explicit references
that will keep the allocations alive in the original frame
(and therefore preserve the memory) until after syscall.Syscall
has returned.
Should fix Solaris flakiness.
This is not a problem for cgo, because cgo wrappers have
correctly typed arguments.
LGTM=iant, khr, aram, rlh
R=iant, khr, bradfitz, aram, rlh
CC=dvyukov, golang-codereviews, r
https://golang.org/cl/139360044
enforce rule: all kernel data structures and constants
go in syscall module.
move things that should be in syscall out of net.
make net a single package.
R=r
OCL=15985
CL=15994
use -j4 (4-way parallel) in make.bash.
halves time for make.bash on r45
also add libregexp, acid to default build
R=r
DELTA=90 (39 added, 37 deleted, 14 changed)
OCL=15485
CL=15487
tweak os to adjust
move StringToBytes into syscall, at least for now
this program still works:
package main
import os "os"
func main() {
os.Stdout.WriteString("hello, world\n");
a, b := os.NewFD(77).WriteString("no way");
os.Stdout.WriteString(b.String() + "\n");
}
R=rsc
DELTA=263 (59 added, 176 deleted, 28 changed)
OCL=15153
CL=15153
* kick off new os procs (machs) as needed
* add sys·sleep for testing
* add Lock, Rendez
* properly lock mal, sys·newproc, scheduler
* linux syscall arg #4 is in R10, not CX
* chans are not multithread-safe yet
* multithreading disabled by default;
set $gomaxprocs=2 (or 1000) to turn it on
This should build on OS X but may not.
Rob and I will fix soon after submitting.
TBR=r
OCL=13784
CL=13842
