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runtime: tweak js and plan9 to avoid/disable write barrier & gc problems

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runtime code for js contains possible write barriers that fail
the nowritebarrierrec check when internal local package naming
conventions are changed.  The problem was there all already; this
allows the code to compile, and it seems to work anyway in the
(single-threaded) js/wasm environment.  The offending operations
are noted with TODO, which is an improvement.

runtime code for plan9 contained an apparent allocation that was
not really an allocation; rewrite to remove the potential allocation
to avoid nowritebarrierrec problems.

This CL is a prerequisite for a pending code cleanup,
https://go-review.googlesource.com/c/go/+/393715

Updates #51734.

Change-Id: I93f31831ff9b92632137dd7b0055eaa721c81556
Reviewed-on: https://go-review.googlesource.com/c/go/+/405901
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
David Chase 2022-05-13 13:16:58 -04:00
parent 540f8c2b50
commit 364ced6255
3 changed files with 12 additions and 2 deletions
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8
src/runtime/lock_js.go
View File

@ -144,8 +144,12 @@ func notetsleepg(n *note, ns int64) bool {
}
// checkTimeouts resumes goroutines that are waiting on a note which has reached its deadline.
// TODO(drchase): need to understand if write barriers are really okay in this context.
//
//go:yeswritebarrierrec
func checkTimeouts() {
now := nanotime()
// TODO: map iteration has the write barriers in it; is that okay?
for n, nt := range notesWithTimeout {
if n.key == note_cleared && now >= nt.deadline {
n.key = note_timeout
@ -175,6 +179,9 @@ var idleID int32
// If an event handler returned, we resume it and it will pause the execution.
// beforeIdle either returns the specific goroutine to schedule next or
// indicates with otherReady that some goroutine became ready.
// TODO(drchase): need to understand if write barriers are really okay in this context.
//
//go:yeswritebarrierrec
func beforeIdle(now, pollUntil int64) (gp *g, otherReady bool) {
delay := int64(-1)
if pollUntil != 0 {
@ -196,6 +203,7 @@ func beforeIdle(now, pollUntil int64) (gp *g, otherReady bool) {
}
if len(events) == 0 {
// TODO: this is the line that requires the yeswritebarrierrec
go handleAsyncEvent()
return nil, true
}

2
src/runtime/os_js.go
View File

@ -129,7 +129,7 @@ func initsig(preinit bool) {
//
//go:nowritebarrier
func newosproc(mp *m) {
panic("newosproc: not implemented")
throw("newosproc: not implemented")
}
func setProcessCPUProfiler(hz int32) {}

4
src/runtime/os_plan9.go
View File

@ -437,7 +437,9 @@ func exit(e int32) {
} else {
// build error string
var tmp [32]byte
status = append(itoa(tmp[:len(tmp)-1], uint64(e)), 0)
sl := itoa(tmp[:len(tmp)-1], uint64(e))
// Don't append, rely on the existing data being zero.
status = tmp[:len(sl)+1]
}
goexitsall(&status[0])
exits(&status[0])