| 351 |
|
* progress. Resizing proceeds by transferring bins, one by one, |
| 352 |
|
* from the table to the next table. However, threads claim small |
| 353 |
|
* blocks of indices to transfer (via field transferIndex) before |
| 354 |
< |
* doing so, reducing contention. Because we are using |
| 355 |
< |
* power-of-two expansion, the elements from each bin must either |
| 356 |
< |
* stay at same index, or move with a power of two offset. We |
| 357 |
< |
* eliminate unnecessary node creation by catching cases where old |
| 358 |
< |
* nodes can be reused because their next fields won't change. On |
| 359 |
< |
* average, only about one-sixth of them need cloning when a table |
| 360 |
< |
* doubles. The nodes they replace will be garbage collectable as |
| 361 |
< |
* soon as they are no longer referenced by any reader thread that |
| 362 |
< |
* may be in the midst of concurrently traversing table. Upon |
| 363 |
< |
* transfer, the old table bin contains only a special forwarding |
| 364 |
< |
* node (with hash field "MOVED") that contains the next table as |
| 365 |
< |
* its key. On encountering a forwarding node, access and update |
| 366 |
< |
* operations restart, using the new table. |
| 354 |
> |
* doing so, reducing contention. A generation stamp in field |
| 355 |
> |
* sizeCtl ensures that resizings do not overlap. Because we are |
| 356 |
> |
* using power-of-two expansion, the elements from each bin must |
| 357 |
> |
* either stay at same index, or move with a power of two |
| 358 |
> |
* offset. We eliminate unnecessary node creation by catching |
| 359 |
> |
* cases where old nodes can be reused because their next fields |
| 360 |
> |
* won't change. On average, only about one-sixth of them need |
| 361 |
> |
* cloning when a table doubles. The nodes they replace will be |
| 362 |
> |
* garbage collectable as soon as they are no longer referenced by |
| 363 |
> |
* any reader thread that may be in the midst of concurrently |
| 364 |
> |
* traversing table. Upon transfer, the old table bin contains |
| 365 |
> |
* only a special forwarding node (with hash field "MOVED") that |
| 366 |
> |
* contains the next table as its key. On encountering a |
| 367 |
> |
* forwarding node, access and update operations restart, using |
| 368 |
> |
* the new table. |
| 369 |
|
* |
| 370 |
|
* Each bin transfer requires its bin lock, which can stall |
| 371 |
|
* waiting for locks while resizing. However, because other |
| 542 |
|
*/ |
| 543 |
|
private static final int MIN_TRANSFER_STRIDE = 16; |
| 544 |
|
|
| 545 |
+ |
/** |
| 546 |
+ |
* The number of bits used for generation stamp in sizeCtl. |
| 547 |
+ |
* Must be at least 6 for 32bit arrays. |
| 548 |
+ |
*/ |
| 549 |
+ |
private static int RESIZE_STAMP_BITS = 16; |
| 550 |
+ |
|
| 551 |
+ |
/** |
| 552 |
+ |
* The maximum number of threads that can help resize. |
| 553 |
+ |
* Must fit in 32 - RESIZE_STAMP_BITS bits. |
| 554 |
+ |
*/ |
| 555 |
+ |
private static final int MAX_RESIZERS = (1 << (32 - RESIZE_STAMP_BITS)) - 1; |
| 556 |
+ |
|
| 557 |
+ |
/** |
| 558 |
+ |
* The bit shift for recording size stamp in sizeCtl. |
| 559 |
+ |
*/ |
| 560 |
+ |
private static final int RESIZE_STAMP_SHIFT = 32 - RESIZE_STAMP_BITS; |
| 561 |
+ |
|
| 562 |
|
/* |
| 563 |
|
* Encodings for Node hash fields. See above for explanation. |
| 564 |
|
*/ |
| 716 |
|
* errors by users, these checks must operate on local variables, |
| 717 |
|
* which accounts for some odd-looking inline assignments below. |
| 718 |
|
* Note that calls to setTabAt always occur within locked regions, |
| 719 |
< |
* and so in principle require only release ordering, not need |
| 719 |
> |
* and so in principle require only release ordering, not |
| 720 |
|
* full volatile semantics, but are currently coded as volatile |
| 721 |
|
* writes to be conservative. |
| 722 |
|
*/ |
| 2184 |
|
/* ---------------- Table Initialization and Resizing -------------- */ |
| 2185 |
|
|
| 2186 |
|
/** |
| 2187 |
+ |
* Returns the stamp bits for resizing a table of size n. |
| 2188 |
+ |
* Must be negative when shifted left by RESIZE_STAMP_SHIFT. |
| 2189 |
+ |
*/ |
| 2190 |
+ |
static final int resizeStamp(int n) { |
| 2191 |
+ |
return Integer.numberOfLeadingZeros(n) | (1 << (RESIZE_STAMP_BITS - 1)); |
| 2192 |
+ |
} |
| 2193 |
+ |
|
| 2194 |
+ |
/** |
| 2195 |
|
* Initializes table, using the size recorded in sizeCtl. |
| 2196 |
|
*/ |
| 2197 |
|
private final Node<K,V>[] initTable() { |
| 2245 |
|
s = sumCount(); |
| 2246 |
|
} |
| 2247 |
|
if (check >= 0) { |
| 2248 |
< |
Node<K,V>[] tab, nt; int sc; |
| 2248 |
> |
Node<K,V>[] tab, nt; int n, sc; |
| 2249 |
|
while (s >= (long)(sc = sizeCtl) && (tab = table) != null && |
| 2250 |
< |
tab.length < MAXIMUM_CAPACITY) { |
| 2250 |
> |
(n = tab.length) < MAXIMUM_CAPACITY) { |
| 2251 |
> |
int rs = resizeStamp(n); |
| 2252 |
|
if (sc < 0) { |
| 2253 |
< |
if (sc == -1 || transferIndex <= 0 || |
| 2254 |
< |
(nt = nextTable) == null) |
| 2253 |
> |
if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 || |
| 2254 |
> |
sc == rs + MAX_RESIZERS || (nt = nextTable) == null || |
| 2255 |
> |
transferIndex <= 0) |
| 2256 |
|
break; |
| 2257 |
< |
if (U.compareAndSwapInt(this, SIZECTL, sc, sc - 1)) |
| 2257 |
> |
if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) |
| 2258 |
|
transfer(tab, nt); |
| 2259 |
|
} |
| 2260 |
< |
else if (U.compareAndSwapInt(this, SIZECTL, sc, -2)) |
| 2260 |
> |
else if (U.compareAndSwapInt(this, SIZECTL, sc, |
| 2261 |
> |
(rs << RESIZE_STAMP_SHIFT) + 2)) |
| 2262 |
|
transfer(tab, null); |
| 2263 |
|
s = sumCount(); |
| 2264 |
|
} |
| 2270 |
|
*/ |
| 2271 |
|
final Node<K,V>[] helpTransfer(Node<K,V>[] tab, Node<K,V> f) { |
| 2272 |
|
Node<K,V>[] nextTab; int sc; |
| 2273 |
< |
if ((f instanceof ForwardingNode) && |
| 2273 |
> |
if (tab != null && (f instanceof ForwardingNode) && |
| 2274 |
|
(nextTab = ((ForwardingNode<K,V>)f).nextTable) != null) { |
| 2275 |
< |
while (transferIndex > 0 && nextTab == nextTable && |
| 2276 |
< |
(sc = sizeCtl) < -1) { |
| 2277 |
< |
if (U.compareAndSwapInt(this, SIZECTL, sc, sc - 1)) { |
| 2275 |
> |
int rs = resizeStamp(tab.length); |
| 2276 |
> |
while (nextTab == nextTable && table == tab && |
| 2277 |
> |
(sc = sizeCtl) < 0) { |
| 2278 |
> |
if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 || |
| 2279 |
> |
sc == rs + MAX_RESIZERS || transferIndex <= 0) |
| 2280 |
> |
break; |
| 2281 |
> |
if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) { |
| 2282 |
|
transfer(tab, nextTab); |
| 2283 |
|
break; |
| 2284 |
|
} |
| 2316 |
|
} |
| 2317 |
|
else if (c <= sc || n >= MAXIMUM_CAPACITY) |
| 2318 |
|
break; |
| 2319 |
< |
else if (tab == table && |
| 2320 |
< |
U.compareAndSwapInt(this, SIZECTL, sc, -2)) |
| 2321 |
< |
transfer(tab, null); |
| 2319 |
> |
else if (tab == table) { |
| 2320 |
> |
int rs = resizeStamp(n); |
| 2321 |
> |
if (sc < 0) { |
| 2322 |
> |
Node<K,V>[] nt; |
| 2323 |
> |
if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 || |
| 2324 |
> |
sc == rs + MAX_RESIZERS || (nt = nextTable) == null || |
| 2325 |
> |
transferIndex <= 0) |
| 2326 |
> |
break; |
| 2327 |
> |
if (U.compareAndSwapInt(this, SIZECTL, sc, sc + 1)) |
| 2328 |
> |
transfer(tab, nt); |
| 2329 |
> |
} |
| 2330 |
> |
else if (U.compareAndSwapInt(this, SIZECTL, sc, |
| 2331 |
> |
(rs << RESIZE_STAMP_SHIFT) + 2)) |
| 2332 |
> |
transfer(tab, null); |
| 2333 |
> |
} |
| 2334 |
|
} |
| 2335 |
|
} |
| 2336 |
|
|
| 2385 |
|
sizeCtl = (n << 1) - (n >>> 1); |
| 2386 |
|
return; |
| 2387 |
|
} |
| 2388 |
< |
if (U.compareAndSwapInt(this, SIZECTL, sc = sizeCtl, ++sc)) { |
| 2389 |
< |
if (sc != -1) |
| 2388 |
> |
if (U.compareAndSwapInt(this, SIZECTL, sc = sizeCtl, sc - 1)) { |
| 2389 |
> |
if ((sc - 2) != resizeStamp(n)) |
| 2390 |
|
return; |
| 2391 |
|
finishing = advance = true; |
| 2392 |
|
i = n; // recheck before commit |
| 2585 |
|
private final void treeifyBin(Node<K,V>[] tab, int index) { |
| 2586 |
|
Node<K,V> b; int n, sc; |
| 2587 |
|
if (tab != null) { |
| 2588 |
< |
if ((n = tab.length) < MIN_TREEIFY_CAPACITY) { |
| 2589 |
< |
if (tab == table && (sc = sizeCtl) >= 0 && |
| 2544 |
< |
U.compareAndSwapInt(this, SIZECTL, sc, -2)) |
| 2545 |
< |
transfer(tab, null); |
| 2546 |
< |
} |
| 2588 |
> |
if ((n = tab.length) < MIN_TREEIFY_CAPACITY) |
| 2589 |
> |
tryPresize(n << 1); |
| 2590 |
|
else if ((b = tabAt(tab, index)) != null && b.hash >= 0) { |
| 2591 |
|
synchronized (b) { |
| 2592 |
|
if (tabAt(tab, index) == b) { |
| 2784 |
|
private final void contendedLock() { |
| 2785 |
|
boolean waiting = false; |
| 2786 |
|
for (int s;;) { |
| 2787 |
< |
if (((s = lockState) & WRITER) == 0) { |
| 2787 |
> |
if (((s = lockState) & ~WAITER) == 0) { |
| 2788 |
|
if (U.compareAndSwapInt(this, LOCKSTATE, s, WRITER)) { |
| 2789 |
|
if (waiting) |
| 2790 |
|
waiter = null; |
