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runtime: convert prof.hz to atomic type

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This converts several unsynchronized reads (reads without holding
prof.signalLock) into atomic reads.

For #53821.
For #52912.

Change-Id: I421b96a22fbe26d699bcc21010c8a9e0f4efc276
Reviewed-on: https://go-review.googlesource.com/c/go/+/420196
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Michael Pratt 2022-07-29 14:48:48 -04:00
parent 3121c2bf64
commit 54cf1b107d
3 changed files with 11 additions and 8 deletions
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13
src/runtime/proc.go
View file

@ -4475,7 +4475,10 @@ func mcount() int32 {
var prof struct {
signalLock atomic.Uint32
hz int32
// Must hold signalLock to write. Reads may be lock-free, but
// signalLock should be taken to synchronize with changes.
hz atomic.Int32
}
func _System() { _System() }
@ -4490,7 +4493,7 @@ func _VDSO() { _VDSO() }
//
//go:nowritebarrierrec
func sigprof(pc, sp, lr uintptr, gp *g, mp *m) {
if prof.hz == 0 {
if prof.hz.Load() == 0 {
return
}
@ -4587,7 +4590,7 @@ func sigprof(pc, sp, lr uintptr, gp *g, mp *m) {
}
}
if prof.hz != 0 {
if prof.hz.Load() != 0 {
// Note: it can happen on Windows that we interrupted a system thread
// with no g, so gp could nil. The other nil checks are done out of
// caution, but not expected to be nil in practice.
@ -4631,9 +4634,9 @@ func setcpuprofilerate(hz int32) {
for !prof.signalLock.CompareAndSwap(0, 1) {
osyield()
}
if prof.hz != hz {
if prof.hz.Load() != hz {
setProcessCPUProfiler(hz)
prof.hz = hz
prof.hz.Store(hz)
}
prof.signalLock.Store(0)