[release-branch.go1.20] runtime: set raceignore to zero when starting a new goroutine

When reusing a g struct the runtime did not reset
g.raceignore. Initialize raceignore to zero when initially
setting racectx.

A goroutine can end with a non-zero raceignore if it exits
after calling runtime.RaceDisable without a matching
runtime.RaceEnable. If that goroutine's g is later reused
the race detector is in a weird state: the underlying
g.racectx is active, yet g.raceignore is non-zero, and
raceacquire/racerelease which check g.raceignore become
no-ops. This causes the race detector to report races when
there are none.

For #60934
Fixes #60949

Change-Id: Ib8e412f11badbaf69a480f03740da70891f4093f
Reviewed-on: https://go-review.googlesource.com/c/go/+/505055
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
(cherry picked from commit 48dbb6227acf3ebc8ac21924567aa2b6d5064915)
Reviewed-on: https://go-review.googlesource.com/c/go/+/505676
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>

diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index bf2a33ea92aa80719dc62a25cd23ede9f2aab3e0..96908fc6a5e2cd9f39f41b668a2b905d32f40e4c 100644 (file)
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -4351,6 +4351,7 @@ func newproc1(fn *funcval, callergp *g, callerpc uintptr) *g {
        pp.goidcache++
        if raceenabled {
                newg.racectx = racegostart(callerpc)
+               newg.raceignore = 0
                if newg.labels != nil {
                        // See note in proflabel.go on labelSync's role in synchronizing
                        // with the reads in the signal handler.

diff --git a/src/runtime/race/testdata/mop_test.go b/src/runtime/race/testdata/mop_test.go
index 0d79091df46676abcb3ec70170cf2c5a74aaa604..4a9ce2631edc6f46e1d4a0a912f105029610e629 100644 (file)
--- a/src/runtime/race/testdata/mop_test.go
+++ b/src/runtime/race/testdata/mop_test.go
@@ -2092,3 +2092,40 @@ func TestNoRaceTinyAlloc(t *testing.T) {
                <-done
        }
 }
+
+func TestNoRaceIssue60934(t *testing.T) {
+       // Test that runtime.RaceDisable state doesn't accidentally get applied to
+       // new goroutines.
+
+       // Create several goroutines that end after calling runtime.RaceDisable.
+       var wg sync.WaitGroup
+       ready := make(chan struct{})
+       wg.Add(32)
+       for i := 0; i < 32; i++ {
+               go func() {
+                       <-ready // ensure we have multiple goroutines running at the same time
+                       runtime.RaceDisable()
+                       wg.Done()
+               }()
+       }
+       close(ready)
+       wg.Wait()
+
+       // Make sure race detector still works. If the runtime.RaceDisable state
+       // leaks, the happens-before edges here will be ignored and a race on x will
+       // be reported.
+       var x int
+       ch := make(chan struct{}, 0)
+       wg.Add(2)
+       go func() {
+               x = 1
+               ch <- struct{}{}
+               wg.Done()
+       }()
+       go func() {
+               <-ch
+               _ = x
+               wg.Done()
+       }()
+       wg.Wait()
+}