// atomicstorep performs *ptr = new atomically and invokes a write barrier.
//
//go:nosplit
func atomicstorep(ptr unsafe.Pointer, new unsafe.Pointer) {
atomic.StorepNoWB(noescape(ptr), new)
writebarrierptr_nostore((*uintptr)(ptr), uintptr(new))
}
// Temporary for gccgo until we port atomic_pointer.go.
//go:nosplit
func atomicstorep(ptr unsafe.Pointer, new unsafe.Pointer) {
atomic.StorepNoWB(noescape(ptr), new)
}
// push adds span s to buffer b. push is safe to call concurrently
// with other push operations, but NOT to call concurrently with pop.
func (b *gcSweepBuf) push(s *mspan) {
// Obtain our slot.
cursor := uintptr(atomic.Xadd(&b.index, +1) - 1)
top, bottom := cursor/gcSweepBlockEntries, cursor%gcSweepBlockEntries
// Do we need to add a block?
spineLen := atomic.Loaduintptr(&b.spineLen)
var block *gcSweepBlock
retry:
if top < spineLen {
spine := atomic.Loadp(unsafe.Pointer(&b.spine))
blockp := add(spine, sys.PtrSize*top)
block = (*gcSweepBlock)(atomic.Loadp(blockp))
} else {
// Add a new block to the spine, potentially growing
// the spine.
lock(&b.spineLock)
// spineLen cannot change until we release the lock,
// but may have changed while we were waiting.
spineLen = atomic.Loaduintptr(&b.spineLen)
if top < spineLen {
unlock(&b.spineLock)
goto retry
}
if spineLen == b.spineCap {
// Grow the spine.
newCap := b.spineCap * 2
if newCap == 0 {
newCap = gcSweepBufInitSpineCap
}
newSpine := persistentalloc(newCap*sys.PtrSize, sys.CacheLineSize, &memstats.gc_sys)
if b.spineCap != 0 {
// Blocks are allocated off-heap, so
// no write barriers.
memmove(newSpine, b.spine, b.spineCap*sys.PtrSize)
}
// Spine is allocated off-heap, so no write barrier.
atomic.StorepNoWB(unsafe.Pointer(&b.spine), newSpine)
b.spineCap = newCap
// We can't immediately free the old spine
// since a concurrent push with a lower index
// could still be reading from it. We let it
// leak because even a 1TB heap would waste
// less than 2MB of memory on old spines. If
// this is a problem, we could free old spines
// during STW.
}
// Allocate a new block and add it to the spine.
block = (*gcSweepBlock)(persistentalloc(unsafe.Sizeof(gcSweepBlock{}), sys.CacheLineSize, &memstats.gc_sys))
blockp := add(b.spine, sys.PtrSize*top)
// Blocks are allocated off-heap, so no write barrier.
atomic.StorepNoWB(blockp, unsafe.Pointer(block))
atomic.Storeuintptr(&b.spineLen, spineLen+1)
unlock(&b.spineLock)
}
// We have a block. Insert the span.
block.spans[bottom] = s
}