runtime: swap the order of raceacquire() and racerelease()
In chansend() and chanrecv() of chan.go, the order of calls to
raceacquire() and racerelease() was swapped, which meant that the
code was not following the memory model "by the letter of the law."
Similar for bufrecv and bufsend in select.go
The memory model says:
- A send happens before the corresponding receive completes, and
- the kth receive on a channel with capacity C happens before the
k+C send on that channel completes.
The operative word here is "completes." For example, a sender obtains
happens-before information on completion of the send-operation, which
means, after the sender has deposited its message onto the channel.
Similarly for receives.
If the order of raceacquire() and racerelease() is incorrect, the race
detector may fail to report some race conditions.
The fix is minimal from the point of view of Go. The fix does, however,
rely on a new function added to TSan:
https://reviews.llvm.org/D76322
This commit only affects execution when race detection is enabled.
Added two tests into `runtime/race/output_test.go`:
- `chanmm` tests for the issue addressed by this patch
- `mutex` is a test for inverted semaphores, which must not be broken
by this (or any other) patch
Fixes #37355
Change-Id: I5e886879ead2bd456a4b7dd1d17253641b767f63
Reviewed-on: https://go-review.googlesource.com/c/go/+/220419
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
diff --git a/src/runtime/chan.go b/src/runtime/chan.go
index 859f36c..254816e 100644
--- a/src/runtime/chan.go
+++ b/src/runtime/chan.go
@@ -215,8 +215,7 @@
// Space is available in the channel buffer. Enqueue the element to send.
qp := chanbuf(c, c.sendx)
if raceenabled {
- raceacquire(qp)
- racerelease(qp)
+ racereleaseacquire(qp)
}
typedmemmove(c.elemtype, qp, ep)
c.sendx++
@@ -299,10 +298,8 @@
// we copy directly. Note that we need to increment
// the head/tail locations only when raceenabled.
qp := chanbuf(c, c.recvx)
- raceacquire(qp)
- racerelease(qp)
- raceacquireg(sg.g, qp)
- racereleaseg(sg.g, qp)
+ racereleaseacquire(qp)
+ racereleaseacquireg(sg.g, qp)
c.recvx++
if c.recvx == c.dataqsiz {
c.recvx = 0
@@ -535,8 +532,7 @@
// Receive directly from queue
qp := chanbuf(c, c.recvx)
if raceenabled {
- raceacquire(qp)
- racerelease(qp)
+ racereleaseacquire(qp)
}
if ep != nil {
typedmemmove(c.elemtype, ep, qp)
@@ -625,10 +621,8 @@
// queue is full, those are both the same slot.
qp := chanbuf(c, c.recvx)
if raceenabled {
- raceacquire(qp)
- racerelease(qp)
- raceacquireg(sg.g, qp)
- racereleaseg(sg.g, qp)
+ racereleaseacquire(qp)
+ racereleaseacquireg(sg.g, qp)
}
// copy data from queue to receiver
if ep != nil {
diff --git a/src/runtime/race.go b/src/runtime/race.go
index 53910f9..79fd217 100644
--- a/src/runtime/race.go
+++ b/src/runtime/race.go
@@ -268,6 +268,9 @@
//go:linkname __tsan_release __tsan_release
var __tsan_release byte
+//go:linkname __tsan_release_acquire __tsan_release_acquire
+var __tsan_release_acquire byte
+
//go:linkname __tsan_release_merge __tsan_release_merge
var __tsan_release_merge byte
@@ -293,6 +296,7 @@
//go:cgo_import_static __tsan_free
//go:cgo_import_static __tsan_acquire
//go:cgo_import_static __tsan_release
+//go:cgo_import_static __tsan_release_acquire
//go:cgo_import_static __tsan_release_merge
//go:cgo_import_static __tsan_go_ignore_sync_begin
//go:cgo_import_static __tsan_go_ignore_sync_end
@@ -536,6 +540,19 @@
}
//go:nosplit
+func racereleaseacquire(addr unsafe.Pointer) {
+ racereleaseacquireg(getg(), addr)
+}
+
+//go:nosplit
+func racereleaseacquireg(gp *g, addr unsafe.Pointer) {
+ if getg().raceignore != 0 || !isvalidaddr(addr) {
+ return
+ }
+ racecall(&__tsan_release_acquire, gp.racectx, uintptr(addr), 0, 0)
+}
+
+//go:nosplit
func racereleasemerge(addr unsafe.Pointer) {
racereleasemergeg(getg(), addr)
}
diff --git a/src/runtime/race/output_test.go b/src/runtime/race/output_test.go
index b4b8936..5d0192f 100644
--- a/src/runtime/race/output_test.go
+++ b/src/runtime/race/output_test.go
@@ -338,4 +338,77 @@
--- FAIL: TestFail \(0...s\)
.*testing.go:.*: race detected during execution of test
FAIL`},
+ {"mutex", "run", "", "atexit_sleep_ms=0", `
+package main
+import (
+ "sync"
+ "fmt"
+)
+func main() {
+ c := make(chan bool, 1)
+ threads := 1
+ iterations := 20000
+ data := 0
+ var wg sync.WaitGroup
+ for i := 0; i < threads; i++ {
+ wg.Add(1)
+ go func() {
+ defer wg.Done()
+ for i := 0; i < iterations; i++ {
+ c <- true
+ data += 1
+ <- c
+ }
+ }()
+ }
+ for i := 0; i < iterations; i++ {
+ c <- true
+ data += 1
+ <- c
+ }
+ wg.Wait()
+ if (data == iterations*(threads+1)) { fmt.Println("pass") }
+}`, `pass`},
+ // Test for https://github.com/golang/go/issues/37355
+ {"chanmm", "run", "", "atexit_sleep_ms=0", `
+package main
+import (
+ "sync"
+ "time"
+)
+func main() {
+ c := make(chan bool, 1)
+ var data uint64
+ var wg sync.WaitGroup
+ wg.Add(2)
+ c <- true
+ go func() {
+ defer wg.Done()
+ c <- true
+ }()
+ go func() {
+ defer wg.Done()
+ time.Sleep(time.Second)
+ <-c
+ data = 2
+ }()
+ data = 1
+ <-c
+ wg.Wait()
+ _ = data
+}
+`, `==================
+WARNING: DATA RACE
+Write at 0x[0-9,a-f]+ by goroutine [0-9]:
+ main\.main\.func2\(\)
+ .*/main\.go:21 \+0x[0-9,a-f]+
+
+Previous write at 0x[0-9,a-f]+ by main goroutine:
+ main\.main\(\)
+ .*/main\.go:23 \+0x[0-9,a-f]+
+
+Goroutine [0-9] \(running\) created at:
+ main\.main\(\)
+ .*/main.go:[0-9]+ \+0x[0-9,a-f]+
+==================`},
}
diff --git a/src/runtime/race0.go b/src/runtime/race0.go
index 6f26afa..180f707 100644
--- a/src/runtime/race0.go
+++ b/src/runtime/race0.go
@@ -32,6 +32,8 @@
func raceacquirectx(racectx uintptr, addr unsafe.Pointer) { throw("race") }
func racerelease(addr unsafe.Pointer) { throw("race") }
func racereleaseg(gp *g, addr unsafe.Pointer) { throw("race") }
+func racereleaseacquire(addr unsafe.Pointer) { throw("race") }
+func racereleaseacquireg(gp *g, addr unsafe.Pointer) { throw("race") }
func racereleasemerge(addr unsafe.Pointer) { throw("race") }
func racereleasemergeg(gp *g, addr unsafe.Pointer) { throw("race") }
func racefingo() { throw("race") }
diff --git a/src/runtime/select.go b/src/runtime/select.go
index 41e68a3..f04b130 100644
--- a/src/runtime/select.go
+++ b/src/runtime/select.go
@@ -415,8 +415,7 @@
if cas.elem != nil {
raceWriteObjectPC(c.elemtype, cas.elem, casePC(casi), chanrecvpc)
}
- raceacquire(chanbuf(c, c.recvx))
- racerelease(chanbuf(c, c.recvx))
+ racereleaseacquire(chanbuf(c, c.recvx))
}
if msanenabled && cas.elem != nil {
msanwrite(cas.elem, c.elemtype.size)
@@ -438,8 +437,7 @@
bufsend:
// can send to buffer
if raceenabled {
- raceacquire(chanbuf(c, c.sendx))
- racerelease(chanbuf(c, c.sendx))
+ racereleaseacquire(chanbuf(c, c.sendx))
raceReadObjectPC(c.elemtype, cas.elem, casePC(casi), chansendpc)
}
if msanenabled {
