| 389 |
|
* progress. Resizing proceeds by transferring bins, one by one, |
| 390 |
|
* from the table to the next table. However, threads claim small |
| 391 |
|
* blocks of indices to transfer (via field transferIndex) before |
| 392 |
< |
* doing so, reducing contention. Because we are using |
| 393 |
< |
* power-of-two expansion, the elements from each bin must either |
| 394 |
< |
* stay at same index, or move with a power of two offset. We |
| 395 |
< |
* eliminate unnecessary node creation by catching cases where old |
| 396 |
< |
* nodes can be reused because their next fields won't change. On |
| 397 |
< |
* average, only about one-sixth of them need cloning when a table |
| 398 |
< |
* doubles. The nodes they replace will be garbage collectable as |
| 399 |
< |
* soon as they are no longer referenced by any reader thread that |
| 400 |
< |
* may be in the midst of concurrently traversing table. Upon |
| 401 |
< |
* transfer, the old table bin contains only a special forwarding |
| 402 |
< |
* node (with hash field "MOVED") that contains the next table as |
| 403 |
< |
* its key. On encountering a forwarding node, access and update |
| 404 |
< |
* operations restart, using the new table. |
| 392 |
> |
* doing so, reducing contention. A generation stamp in field |
| 393 |
> |
* sizeCtl ensures that resizings do not overlap. Because we are |
| 394 |
> |
* using power-of-two expansion, the elements from each bin must |
| 395 |
> |
* either stay at same index, or move with a power of two |
| 396 |
> |
* offset. We eliminate unnecessary node creation by catching |
| 397 |
> |
* cases where old nodes can be reused because their next fields |
| 398 |
> |
* won't change. On average, only about one-sixth of them need |
| 399 |
> |
* cloning when a table doubles. The nodes they replace will be |
| 400 |
> |
* garbage collectable as soon as they are no longer referenced by |
| 401 |
> |
* any reader thread that may be in the midst of concurrently |
| 402 |
> |
* traversing table. Upon transfer, the old table bin contains |
| 403 |
> |
* only a special forwarding node (with hash field "MOVED") that |
| 404 |
> |
* contains the next table as its key. On encountering a |
| 405 |
> |
* forwarding node, access and update operations restart, using |
| 406 |
> |
* the new table. |
| 407 |
|
* |
| 408 |
|
* Each bin transfer requires its bin lock, which can stall |
| 409 |
|
* waiting for locks while resizing. However, because other |
| 580 |
|
*/ |
| 581 |
|
private static final int MIN_TRANSFER_STRIDE = 16; |
| 582 |
|
|
| 583 |
+ |
/** |
| 584 |
+ |
* The number of bits used for generation stamp in sizeCtl. |
| 585 |
+ |
* Must be at least 6 for 32bit arrays. |
| 586 |
+ |
*/ |
| 587 |
+ |
private static int RESIZE_STAMP_BITS = 16; |
| 588 |
+ |
|
| 589 |
+ |
/** |
| 590 |
+ |
* The maximum number of threads that can help resize. |
| 591 |
+ |
* Must fit in 32 - RESIZE_STAMP_BITS bits. |
| 592 |
+ |
*/ |
| 593 |
+ |
private static final int MAX_RESIZERS = (1 << (32 - RESIZE_STAMP_BITS)) - 1; |
| 594 |
+ |
|
| 595 |
+ |
/** |
| 596 |
+ |
* The bit shift for recording size stamp in sizeCtl. |
| 597 |
+ |
*/ |
| 598 |
+ |
private static final int RESIZE_STAMP_SHIFT = 32 - RESIZE_STAMP_BITS; |
| 599 |
+ |
|
| 600 |
|
/* |
| 601 |
|
* Encodings for Node hash fields. See above for explanation. |
| 602 |
|
*/ |
| 754 |
|
* errors by users, these checks must operate on local variables, |
| 755 |
|
* which accounts for some odd-looking inline assignments below. |
| 756 |
|
* Note that calls to setTabAt always occur within locked regions, |
| 757 |
< |
* and so in principle require only release ordering, not need |
| 757 |
> |
* and so in principle require only release ordering, not |
| 758 |
|
* full volatile semantics, but are currently coded as volatile |
| 759 |
|
* writes to be conservative. |
| 760 |
|
*/ |
| 2214 |
|
/* ---------------- Table Initialization and Resizing -------------- */ |
| 2215 |
|
|
| 2216 |
|
/** |
| 2217 |
+ |
* Returns the stamp bits for resizing a table of size n. |
| 2218 |
+ |
* Must be negative when shifted left by RESIZE_STAMP_SHIFT. |
| 2219 |
+ |
*/ |
| 2220 |
+ |
static final int resizeStamp(int n) { |
| 2221 |
+ |
return Integer.numberOfLeadingZeros(n) | (1 << (RESIZE_STAMP_BITS - 1)); |
| 2222 |
+ |
} |
| 2223 |
+ |
|
| 2224 |
+ |
/** |
| 2225 |
|
* Initializes table, using the size recorded in sizeCtl. |
| 2226 |
|
*/ |
| 2227 |
|
private final Node<K,V>[] initTable() { |
| 2234 |
|
if ((tab = table) == null || tab.length == 0) { |
| 2235 |
|
int n = (sc > 0) ? sc : DEFAULT_CAPACITY; |
| 2236 |
|
@SuppressWarnings("unchecked") |
| 2237 |
< |
Node<K,V>[] nt = (Node<K,V>[])new Node<?,?>[n]; |
| 2237 |
> |
Node<K,V>[] nt = (Node<K,V>[])new Node<?,?>[n]; |
| 2238 |
|
table = tab = nt; |
| 2239 |
|
sc = n - (n >>> 2); |
| 2240 |
|
} |
| 2276 |
|
s = sumCount(); |
| 2277 |
|
} |
| 2278 |
|
if (check >= 0) { |
| 2279 |
< |
Node<K,V>[] tab, nt; int sc; |
| 2279 |
> |
Node<K,V>[] tab, nt; int n, sc; |
| 2280 |
|
while (s >= (long)(sc = sizeCtl) && (tab = table) != null && |
| 2281 |
< |
tab.length < MAXIMUM_CAPACITY) { |
| 2281 |
> |
(n = tab.length) < MAXIMUM_CAPACITY) { |
| 2282 |
> |
int rs = resizeStamp(n); |
| 2283 |
|
if (sc < 0) { |
| 2284 |
< |
if (sc == -1 || transferIndex <= 0 || |
| 2285 |
< |
(nt = nextTable) == null) |
| 2284 |
> |
if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 || |
| 2285 |
> |
sc == rs + MAX_RESIZERS || (nt = nextTable) == null || |
| 2286 |
> |
transferIndex <= 0) |
| 2287 |
|
break; |
| 2288 |
< |
if (U.compareAndSwapInt(this, SIZECTL, sc, sc - 1)) |
| 2288 |
> |
if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) |
| 2289 |
|
transfer(tab, nt); |
| 2290 |
|
} |
| 2291 |
< |
else if (U.compareAndSwapInt(this, SIZECTL, sc, -2)) |
| 2291 |
> |
else if (U.compareAndSwapInt(this, SIZECTL, sc, |
| 2292 |
> |
(rs << RESIZE_STAMP_SHIFT) + 2)) |
| 2293 |
|
transfer(tab, null); |
| 2294 |
|
s = sumCount(); |
| 2295 |
|
} |
| 2301 |
|
*/ |
| 2302 |
|
final Node<K,V>[] helpTransfer(Node<K,V>[] tab, Node<K,V> f) { |
| 2303 |
|
Node<K,V>[] nextTab; int sc; |
| 2304 |
< |
if ((f instanceof ForwardingNode) && |
| 2304 |
> |
if (tab != null && (f instanceof ForwardingNode) && |
| 2305 |
|
(nextTab = ((ForwardingNode<K,V>)f).nextTable) != null) { |
| 2306 |
< |
while (transferIndex > 0 && nextTab == nextTable && |
| 2307 |
< |
(sc = sizeCtl) < -1) { |
| 2308 |
< |
if (U.compareAndSwapInt(this, SIZECTL, sc, sc - 1)) { |
| 2306 |
> |
int rs = resizeStamp(tab.length); |
| 2307 |
> |
while (nextTab == nextTable && table == tab && |
| 2308 |
> |
(sc = sizeCtl) < 0) { |
| 2309 |
> |
if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 || |
| 2310 |
> |
sc == rs + MAX_RESIZERS || transferIndex <= 0) |
| 2311 |
> |
break; |
| 2312 |
> |
if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) { |
| 2313 |
|
transfer(tab, nextTab); |
| 2314 |
|
break; |
| 2315 |
|
} |
| 2336 |
|
try { |
| 2337 |
|
if (table == tab) { |
| 2338 |
|
@SuppressWarnings("unchecked") |
| 2339 |
< |
Node<K,V>[] nt = (Node<K,V>[])new Node<?,?>[n]; |
| 2339 |
> |
Node<K,V>[] nt = (Node<K,V>[])new Node<?,?>[n]; |
| 2340 |
|
table = nt; |
| 2341 |
|
sc = n - (n >>> 2); |
| 2342 |
|
} |
| 2347 |
|
} |
| 2348 |
|
else if (c <= sc || n >= MAXIMUM_CAPACITY) |
| 2349 |
|
break; |
| 2350 |
< |
else if (tab == table && |
| 2351 |
< |
U.compareAndSwapInt(this, SIZECTL, sc, -2)) |
| 2352 |
< |
transfer(tab, null); |
| 2350 |
> |
else if (tab == table) { |
| 2351 |
> |
int rs = resizeStamp(n); |
| 2352 |
> |
if (sc < 0) { |
| 2353 |
> |
Node<K,V>[] nt; |
| 2354 |
> |
if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 || |
| 2355 |
> |
sc == rs + MAX_RESIZERS || (nt = nextTable) == null || |
| 2356 |
> |
transferIndex <= 0) |
| 2357 |
> |
break; |
| 2358 |
> |
if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) |
| 2359 |
> |
transfer(tab, nt); |
| 2360 |
> |
} |
| 2361 |
> |
else if (U.compareAndSwapInt(this, SIZECTL, sc, |
| 2362 |
> |
(rs << RESIZE_STAMP_SHIFT) + 2)) |
| 2363 |
> |
transfer(tab, null); |
| 2364 |
> |
} |
| 2365 |
|
} |
| 2366 |
|
} |
| 2367 |
|
|
| 2416 |
|
sizeCtl = (n << 1) - (n >>> 1); |
| 2417 |
|
return; |
| 2418 |
|
} |
| 2419 |
< |
if (U.compareAndSwapInt(this, SIZECTL, sc = sizeCtl, ++sc)) { |
| 2420 |
< |
if (sc != -1) |
| 2419 |
> |
if (U.compareAndSwapInt(this, SIZECTL, sc = sizeCtl, sc - 1)) { |
| 2420 |
> |
if ((sc - 2) != resizeStamp(n)) |
| 2421 |
|
return; |
| 2422 |
|
finishing = advance = true; |
| 2423 |
|
i = n; // recheck before commit |
| 2511 |
|
private final void treeifyBin(Node<K,V>[] tab, int index) { |
| 2512 |
|
Node<K,V> b; int n, sc; |
| 2513 |
|
if (tab != null) { |
| 2514 |
< |
if ((n = tab.length) < MIN_TREEIFY_CAPACITY) { |
| 2515 |
< |
if (tab == table && (sc = sizeCtl) >= 0 && |
| 2470 |
< |
U.compareAndSwapInt(this, SIZECTL, sc, -2)) |
| 2471 |
< |
transfer(tab, null); |
| 2472 |
< |
} |
| 2514 |
> |
if ((n = tab.length) < MIN_TREEIFY_CAPACITY) |
| 2515 |
> |
tryPresize(n << 1); |
| 2516 |
|
else if ((b = tabAt(tab, index)) != null && b.hash >= 0) { |
| 2517 |
|
synchronized (b) { |
| 2518 |
|
if (tabAt(tab, index) == b) { |
| 2533 |
|
} |
| 2534 |
|
} |
| 2535 |
|
} |
| 2493 |
– |
|
| 2536 |
|
/** |
| 2537 |
|
* Returns a list on non-TreeNodes replacing those in given list. |
| 2538 |
|
*/ |
| 2709 |
|
private final void contendedLock() { |
| 2710 |
|
boolean waiting = false; |
| 2711 |
|
for (int s;;) { |
| 2712 |
< |
if (((s = lockState) & WRITER) == 0) { |
| 2712 |
> |
if (((s = lockState) & ~WAITER) == 0) { |
| 2713 |
|
if (U.compareAndSwapInt(this, LOCKSTATE, s, WRITER)) { |
| 2714 |
|
if (waiting) |
| 2715 |
|
waiter = null; |
