runtime: convert workType.cycles to internal atomic types

Note that this changes a non-atomic operation to atomic operation in gcStart().

For #53821

Change-Id: I754d254f6f190855144ff62151b6bae673b47867
Reviewed-on: https://go-review.googlesource.com/c/go/+/425776
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Michael Knyszek <mknyszek@google.com>

diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 3361d48abd7f18d97d8c382bbbdc60163fcf2680..8021a56b9a72fd19a1290fedbce27005b35b531a 100644 (file)
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -393,7 +393,7 @@ type workType struct {
        // cycle is sweep termination, mark, mark termination, and
        // sweep. This differs from memstats.numgc, which is
        // incremented at mark termination.
-       cycles uint32
+       cycles atomic.Uint32
 
        // Timing/utilization stats for this cycle.
        stwprocs, maxprocs                 int32
@@ -436,7 +436,7 @@ func GC() {
 
        // Wait until the current sweep termination, mark, and mark
        // termination complete.
-       n := atomic.Load(&work.cycles)
+       n := work.cycles.Load()
        gcWaitOnMark(n)
 
        // We're now in sweep N or later. Trigger GC cycle N+1, which
@@ -451,7 +451,7 @@ func GC() {
        // complete the cycle and because runtime.GC() is often used
        // as part of tests and benchmarks to get the system into a
        // relatively stable and isolated state.
-       for atomic.Load(&work.cycles) == n+1 && sweepone() != ^uintptr(0) {
+       for work.cycles.Load() == n+1 && sweepone() != ^uintptr(0) {
                sweep.nbgsweep++
                Gosched()
        }
@@ -467,7 +467,7 @@ func GC() {
        // First, wait for sweeping to finish. (We know there are no
        // more spans on the sweep queue, but we may be concurrently
        // sweeping spans, so we have to wait.)
-       for atomic.Load(&work.cycles) == n+1 && !isSweepDone() {
+       for work.cycles.Load() == n+1 && !isSweepDone() {
                Gosched()
        }
 
@@ -475,7 +475,7 @@ func GC() {
        // stable heap profile. Only do this if we haven't already hit
        // another mark termination.
        mp := acquirem()
-       cycle := atomic.Load(&work.cycles)
+       cycle := work.cycles.Load()
        if cycle == n+1 || (gcphase == _GCmark && cycle == n+2) {
                mProf_PostSweep()
        }
@@ -488,7 +488,7 @@ func gcWaitOnMark(n uint32) {
        for {
                // Disable phase transitions.
                lock(&work.sweepWaiters.lock)
-               nMarks := atomic.Load(&work.cycles)
+               nMarks := work.cycles.Load()
                if gcphase != _GCmark {
                        // We've already completed this cycle's mark.
                        nMarks++
@@ -565,7 +565,7 @@ func (t gcTrigger) test() bool {
                return lastgc != 0 && t.now-lastgc > forcegcperiod
        case gcTriggerCycle:
                // t.n > work.cycles, but accounting for wraparound.
-               return int32(t.n-work.cycles) > 0
+               return int32(t.n-work.cycles.Load()) > 0
        }
        return true
 }
@@ -672,7 +672,7 @@ func gcStart(trigger gcTrigger) {
        // reclaimed until the next GC cycle.
        clearpools()
 
-       work.cycles++
+       work.cycles.Add(1)
 
        // Assists and workers can start the moment we start
        // the world.

diff --git a/src/runtime/mgcpacer.go b/src/runtime/mgcpacer.go
index 633d181a9d852a2bebcca092652d65d7e1a52302..2e73ac29230ce88c988a162032e203ea0f7c352a 100644 (file)
--- a/src/runtime/mgcpacer.go
+++ b/src/runtime/mgcpacer.go
@@ -1314,7 +1314,7 @@ func setGCPercent(in int32) (out int32) {
        // If we just disabled GC, wait for any concurrent GC mark to
        // finish so we always return with no GC running.
        if in < 0 {
-               gcWaitOnMark(atomic.Load(&work.cycles))
+               gcWaitOnMark(work.cycles.Load())
        }
 
        return out