// Variant of sync/atomic's TestUnaligned64:
func TestUnaligned64(t *testing.T) {
// Unaligned 64-bit atomics on 32-bit systems are
// a continual source of pain. Test that on 32-bit systems they crash
// instead of failing silently.
switch runtime.GOARCH {
default:
if unsafe.Sizeof(int(0)) != 4 {
t.Skip("test only runs on 32-bit systems")
}
case "amd64p32":
// amd64p32 can handle unaligned atomics.
t.Skipf("test not needed on %v", runtime.GOARCH)
}
x := make([]uint32, 4)
up64 := (*uint64)(unsafe.Pointer(&x[1])) // misaligned
p64 := (*int64)(unsafe.Pointer(&x[1])) // misaligned
shouldPanic(t, "Load64", func() { atomic.Load64(up64) })
shouldPanic(t, "Loadint64", func() { atomic.Loadint64(p64) })
shouldPanic(t, "Store64", func() { atomic.Store64(up64, 0) })
shouldPanic(t, "Xadd64", func() { atomic.Xadd64(up64, 1) })
shouldPanic(t, "Xchg64", func() { atomic.Xchg64(up64, 1) })
shouldPanic(t, "Cas64", func() { atomic.Cas64(up64, 1, 2) })
}
// tracestamp returns a consistent sequence number, time stamp pair
// for use in a trace. We need to make sure that time stamp ordering
// (assuming synchronized CPUs) and sequence ordering match.
// To do that, we increment traceseq, grab ticks, and increment traceseq again.
// We treat odd traceseq as a sign that another thread is in the middle
// of the sequence and spin until it is done.
// Not splitting stack to avoid preemption, just in case the call sites
// that used to call xadd64 and cputicks are sensitive to that.
//go:nosplit
func tracestamp() (seq uint64, ts int64) {
seq = atomic.Load64(&traceseq)
for seq&1 != 0 || !atomic.Cas64(&traceseq, seq, seq+1) {
seq = atomic.Load64(&traceseq)
}
ts = cputicks()
atomic.Store64(&traceseq, seq+2)
return seq >> 1, ts
}
func testAtomic64() {
test_z64 = 42
test_x64 = 0
prefetcht0(uintptr(unsafe.Pointer(&test_z64)))
prefetcht1(uintptr(unsafe.Pointer(&test_z64)))
prefetcht2(uintptr(unsafe.Pointer(&test_z64)))
prefetchnta(uintptr(unsafe.Pointer(&test_z64)))
if atomic.Cas64(&test_z64, test_x64, 1) {
throw("cas64 failed")
}
if test_x64 != 0 {
throw("cas64 failed")
}
test_x64 = 42
if !atomic.Cas64(&test_z64, test_x64, 1) {
throw("cas64 failed")
}
if test_x64 != 42 || test_z64 != 1 {
throw("cas64 failed")
}
if atomic.Load64(&test_z64) != 1 {
throw("load64 failed")
}
atomic.Store64(&test_z64, (1<<40)+1)
if atomic.Load64(&test_z64) != (1<<40)+1 {
throw("store64 failed")
}
if atomic.Xadd64(&test_z64, (1<<40)+1) != (2<<40)+2 {
throw("xadd64 failed")
}
if atomic.Load64(&test_z64) != (2<<40)+2 {
throw("xadd64 failed")
}
if atomic.Xchg64(&test_z64, (3<<40)+3) != (2<<40)+2 {
throw("xchg64 failed")
}
if atomic.Load64(&test_z64) != (3<<40)+3 {
throw("xchg64 failed")
}
}
func lfstackpop(head *uint64) unsafe.Pointer {
for {
old := atomic.Load64(head)
if old == 0 {
return nil
}
node := lfstackUnpack(old)
next := atomic.Load64(&node.next)
if atomic.Cas64(head, old, next) {
return unsafe.Pointer(node)
}
}
}
func lfstackpush(head *uint64, node *lfnode) {
node.pushcnt++
new := lfstackPack(node, node.pushcnt)
if node1 := lfstackUnpack(new); node1 != node {
print("runtime: lfstackpush invalid packing: node=", node, " cnt=", hex(node.pushcnt), " packed=", hex(new), " -> node=", node1, "\n")
throw("lfstackpush")
}
for {
old := atomic.Load64(head)
node.next = old
if atomic.Cas64(head, old, new) {
break
}
}
}
func parfordo(desc *parfor) {
// Obtain 0-based thread index.
tid := atomic.Xadd(&desc.thrseq, 1) - 1
if tid >= desc.nthr {
print("tid=", tid, " nthr=", desc.nthr, "\n")
throw("parfor: invalid tid")
}
// If single-threaded, just execute the for serially.
body := desc.body
if desc.nthr == 1 {
for i := uint32(0); i < desc.cnt; i++ {
body(desc, i)
}
return
}
me := &desc.thr[tid]
mypos := &me.pos
for {
for {
// While there is local work,
// bump low index and execute the iteration.
pos := atomic.Xadd64(mypos, 1)
begin := uint32(pos) - 1
end := uint32(pos >> 32)
if begin < end {
body(desc, begin)
continue
}
break
}
// Out of work, need to steal something.
idle := false
for try := uint32(0); ; try++ {
// If we don't see any work for long enough,
// increment the done counter...
if try > desc.nthr*4 && !idle {
idle = true
atomic.Xadd(&desc.done, 1)
}
// ...if all threads have incremented the counter,
// we are done.
extra := uint32(0)
if !idle {
extra = 1
}
if desc.done+extra == desc.nthr {
if !idle {
atomic.Xadd(&desc.done, 1)
}
goto exit
}
// Choose a random victim for stealing.
var begin, end uint32
victim := fastrand1() % (desc.nthr - 1)
if victim >= tid {
victim++
}
victimpos := &desc.thr[victim].pos
for {
// See if it has any work.
pos := atomic.Load64(victimpos)
begin = uint32(pos)
end = uint32(pos >> 32)
if begin+1 >= end {
end = 0
begin = end
break
}
if idle {
atomic.Xadd(&desc.done, -1)
idle = false
}
begin2 := begin + (end-begin)/2
newpos := uint64(begin) | uint64(begin2)<<32
if atomic.Cas64(victimpos, pos, newpos) {
begin = begin2
break
}
}
if begin < end {
// Has successfully stolen some work.
if idle {
throw("parfor: should not be idle")
}
atomic.Store64(mypos, uint64(begin)|uint64(end)<<32)
me.nsteal++
me.nstealcnt += uint64(end) - uint64(begin)
break
}
// Backoff.
if try < desc.nthr {
// nothing
} else if try < 4*desc.nthr {
me.nprocyield++
procyield(20)
} else if !desc.wait {
// If a caller asked not to wait for the others, exit now
// (assume that most work is already done at this point).
if !idle {
atomic.Xadd(&desc.done, 1)
}
goto exit
} else if try < 6*desc.nthr {
me.nosyield++
osyield()
} else {
me.nsleep++
usleep(1)
}
}
}
exit:
atomic.Xadd64(&desc.nsteal, int64(me.nsteal))
atomic.Xadd64(&desc.nstealcnt, int64(me.nstealcnt))
atomic.Xadd64(&desc.nprocyield, int64(me.nprocyield))
atomic.Xadd64(&desc.nosyield, int64(me.nosyield))
atomic.Xadd64(&desc.nsleep, int64(me.nsleep))
me.nsteal = 0
me.nstealcnt = 0
me.nprocyield = 0
me.nosyield = 0
me.nsleep = 0
}
