/js/lib/Socket.IO-node/support/expresso/deps/jscoverage/js/jslock.cpp
http://github.com/onedayitwillmake/RealtimeMultiplayerNodeJs · C++ · 1417 lines · 925 code · 167 blank · 325 comment · 191 complexity · f51a8ffec4b9a470accc045ada4b356f MD5 · raw file
- /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
- *
- * ***** BEGIN LICENSE BLOCK *****
- * Version: MPL 1.1/GPL 2.0/LGPL 2.1
- *
- * The contents of this file are subject to the Mozilla Public License Version
- * 1.1 (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- * http://www.mozilla.org/MPL/
- *
- * Software distributed under the License is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
- * for the specific language governing rights and limitations under the
- * License.
- *
- * The Original Code is Mozilla Communicator client code, released
- * March 31, 1998.
- *
- * The Initial Developer of the Original Code is
- * Netscape Communications Corporation.
- * Portions created by the Initial Developer are Copyright (C) 1998
- * the Initial Developer. All Rights Reserved.
- *
- * Contributor(s):
- *
- * Alternatively, the contents of this file may be used under the terms of
- * either of the GNU General Public License Version 2 or later (the "GPL"),
- * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
- * in which case the provisions of the GPL or the LGPL are applicable instead
- * of those above. If you wish to allow use of your version of this file only
- * under the terms of either the GPL or the LGPL, and not to allow others to
- * use your version of this file under the terms of the MPL, indicate your
- * decision by deleting the provisions above and replace them with the notice
- * and other provisions required by the GPL or the LGPL. If you do not delete
- * the provisions above, a recipient may use your version of this file under
- * the terms of any one of the MPL, the GPL or the LGPL.
- *
- * ***** END LICENSE BLOCK ***** */
- #ifdef JS_THREADSAFE
- /*
- * JS locking stubs.
- */
- #include "jsstddef.h"
- #include <stdlib.h>
- #include <string.h>
- #include "jspubtd.h"
- #include "jsutil.h" /* Added by JSIFY */
- #include "jstypes.h"
- #include "jsbit.h"
- #include "jscntxt.h"
- #include "jsdtoa.h"
- #include "jsgc.h"
- #include "jsfun.h" /* for VALUE_IS_FUNCTION used by *_WRITE_BARRIER */
- #include "jslock.h"
- #include "jsscope.h"
- #include "jsstr.h"
- #define ReadWord(W) (W)
- /* Implement NativeCompareAndSwap. */
- #if defined(_WIN32) && defined(_M_IX86)
- #pragma warning( disable : 4035 )
- JS_BEGIN_EXTERN_C
- extern long __cdecl
- _InterlockedCompareExchange(long *volatile dest, long exchange, long comp);
- JS_END_EXTERN_C
- #pragma intrinsic(_InterlockedCompareExchange)
- static JS_ALWAYS_INLINE int
- NativeCompareAndSwapHelper(jsword *w, jsword ov, jsword nv)
- {
- _InterlockedCompareExchange(w, nv, ov);
- __asm {
- sete al
- }
- }
- static JS_ALWAYS_INLINE int
- NativeCompareAndSwap(jsword *w, jsword ov, jsword nv)
- {
- return (NativeCompareAndSwapHelper(w, ov, nv) & 1);
- }
- #elif defined(XP_MACOSX) || defined(DARWIN)
- #include <libkern/OSAtomic.h>
- static JS_ALWAYS_INLINE int
- NativeCompareAndSwap(jsword *w, jsword ov, jsword nv)
- {
- /* Details on these functions available in the manpage for atomic */
- #if JS_BYTES_PER_WORD == 8 && JS_BYTES_PER_LONG != 8
- return OSAtomicCompareAndSwap64Barrier(ov, nv, (int64_t*) w);
- #else
- return OSAtomicCompareAndSwap32Barrier(ov, nv, (int32_t*) w);
- #endif
- }
- #elif defined(__GNUC__) && defined(__i386__)
- /* Note: This fails on 386 cpus, cmpxchgl is a >= 486 instruction */
- static JS_ALWAYS_INLINE int
- NativeCompareAndSwap(jsword *w, jsword ov, jsword nv)
- {
- unsigned int res;
- __asm__ __volatile__ (
- "lock\n"
- "cmpxchgl %2, (%1)\n"
- "sete %%al\n"
- "andl $1, %%eax\n"
- : "=a" (res)
- : "r" (w), "r" (nv), "a" (ov)
- : "cc", "memory");
- return (int)res;
- }
- #elif defined(__GNUC__) && defined(__x86_64__)
- static JS_ALWAYS_INLINE int
- NativeCompareAndSwap(jsword *w, jsword ov, jsword nv)
- {
- unsigned int res;
- __asm__ __volatile__ (
- "lock\n"
- "cmpxchgq %2, (%1)\n"
- "sete %%al\n"
- "movzbl %%al, %%eax\n"
- : "=a" (res)
- : "r" (w), "r" (nv), "a" (ov)
- : "cc", "memory");
- return (int)res;
- }
- #elif defined(SOLARIS) && defined(sparc) && defined(ULTRA_SPARC)
- static JS_ALWAYS_INLINE int
- NativeCompareAndSwap(jsword *w, jsword ov, jsword nv)
- {
- #if defined(__GNUC__)
- unsigned int res;
- JS_ASSERT(ov != nv);
- asm volatile ("\
- stbar\n\
- cas [%1],%2,%3\n\
- cmp %2,%3\n\
- be,a 1f\n\
- mov 1,%0\n\
- mov 0,%0\n\
- 1:"
- : "=r" (res)
- : "r" (w), "r" (ov), "r" (nv));
- return (int)res;
- #else /* !__GNUC__ */
- extern int compare_and_swap(jsword*, jsword, jsword);
- JS_ASSERT(ov != nv);
- return compare_and_swap(w, ov, nv);
- #endif
- }
- #elif defined(AIX)
- #include <sys/atomic_op.h>
- static JS_ALWAYS_INLINE int
- NativeCompareAndSwap(jsword *w, jsword ov, jsword nv)
- {
- return !_check_lock((atomic_p)w, ov, nv);
- }
- #elif defined(USE_ARM_KUSER)
- /* See https://bugzilla.mozilla.org/show_bug.cgi?id=429387 for a
- * description of this ABI; this is a function provided at a fixed
- * location by the kernel in the memory space of each process.
- */
- typedef int (__kernel_cmpxchg_t)(int oldval, int newval, volatile int *ptr);
- #define __kernel_cmpxchg (*(__kernel_cmpxchg_t *)0xffff0fc0)
- JS_STATIC_ASSERT(sizeof(jsword) == sizeof(int));
- static JS_ALWAYS_INLINE int
- NativeCompareAndSwap(jsword *w, jsword ov, jsword nv)
- {
- volatile int *vp = (volatile int *) w;
- PRInt32 failed = 1;
- /* Loop until a __kernel_cmpxchg succeeds. See bug 446169 */
- do {
- failed = __kernel_cmpxchg(ov, nv, vp);
- } while (failed && *vp == ov);
- return !failed;
- }
- #elif JS_HAS_NATIVE_COMPARE_AND_SWAP
- #error "JS_HAS_NATIVE_COMPARE_AND_SWAP should be 0 if your platform lacks a compare-and-swap instruction."
- #endif /* arch-tests */
- #if JS_HAS_NATIVE_COMPARE_AND_SWAP
- JSBool
- js_CompareAndSwap(jsword *w, jsword ov, jsword nv)
- {
- return !!NativeCompareAndSwap(w, ov, nv);
- }
- #elif defined(NSPR_LOCK)
- # ifdef __GNUC__
- # warning "js_CompareAndSwap is implemented using NSSP lock"
- # endif
- JSBool
- js_CompareAndSwap(jsword *w, jsword ov, jsword nv)
- {
- int result;
- static PRLock *CompareAndSwapLock = JS_NEW_LOCK();
- JS_ACQUIRE_LOCK(CompareAndSwapLock);
- result = (*w == ov);
- if (result)
- *w = nv;
- JS_RELEASE_LOCK(CompareAndSwapLock);
- return result;
- }
- #else /* !defined(NSPR_LOCK) */
- #error "NSPR_LOCK should be on when the platform lacks native compare-and-swap."
- #endif
- #ifndef NSPR_LOCK
- struct JSFatLock {
- int susp;
- PRLock *slock;
- PRCondVar *svar;
- JSFatLock *next;
- JSFatLock **prevp;
- };
- typedef struct JSFatLockTable {
- JSFatLock *free;
- JSFatLock *taken;
- } JSFatLockTable;
- #define GLOBAL_LOCK_INDEX(id) (((uint32)(jsuword)(id)>>2) & global_locks_mask)
- static void
- js_Dequeue(JSThinLock *);
- static PRLock **global_locks;
- static uint32 global_lock_count = 1;
- static uint32 global_locks_log2 = 0;
- static uint32 global_locks_mask = 0;
- static void
- js_LockGlobal(void *id)
- {
- uint32 i = GLOBAL_LOCK_INDEX(id);
- PR_Lock(global_locks[i]);
- }
- static void
- js_UnlockGlobal(void *id)
- {
- uint32 i = GLOBAL_LOCK_INDEX(id);
- PR_Unlock(global_locks[i]);
- }
- #endif /* !NSPR_LOCK */
- void
- js_InitLock(JSThinLock *tl)
- {
- #ifdef NSPR_LOCK
- tl->owner = 0;
- tl->fat = (JSFatLock*)JS_NEW_LOCK();
- #else
- memset(tl, 0, sizeof(JSThinLock));
- #endif
- }
- void
- js_FinishLock(JSThinLock *tl)
- {
- #ifdef NSPR_LOCK
- tl->owner = 0xdeadbeef;
- if (tl->fat)
- JS_DESTROY_LOCK(((JSLock*)tl->fat));
- #else
- JS_ASSERT(tl->owner == 0);
- JS_ASSERT(tl->fat == NULL);
- #endif
- }
- #ifdef DEBUG_SCOPE_COUNT
- #include <stdio.h>
- #include "jsdhash.h"
- static FILE *logfp;
- static JSDHashTable logtbl;
- typedef struct logentry {
- JSDHashEntryStub stub;
- char op;
- const char *file;
- int line;
- } logentry;
- static void
- logit(JSScope *scope, char op, const char *file, int line)
- {
- logentry *entry;
- if (!logfp) {
- logfp = fopen("/tmp/scope.log", "w");
- if (!logfp)
- return;
- setvbuf(logfp, NULL, _IONBF, 0);
- }
- fprintf(logfp, "%p %c %s %d\n", scope, op, file, line);
- if (!logtbl.entryStore &&
- !JS_DHashTableInit(&logtbl, JS_DHashGetStubOps(), NULL,
- sizeof(logentry), 100)) {
- return;
- }
- entry = (logentry *) JS_DHashTableOperate(&logtbl, scope, JS_DHASH_ADD);
- if (!entry)
- return;
- entry->stub.key = scope;
- entry->op = op;
- entry->file = file;
- entry->line = line;
- }
- void
- js_unlog_scope(JSScope *scope)
- {
- if (!logtbl.entryStore)
- return;
- (void) JS_DHashTableOperate(&logtbl, scope, JS_DHASH_REMOVE);
- }
- # define LOGIT(scope,op) logit(scope, op, __FILE__, __LINE__)
- #else
- # define LOGIT(scope,op) /* nothing */
- #endif /* DEBUG_SCOPE_COUNT */
- /*
- * Return true if scope's ownercx, or the ownercx of a single-threaded scope
- * for which ownercx is waiting to become multi-threaded and shared, is cx.
- * That condition implies deadlock in ClaimScope if cx's thread were to wait
- * to share scope.
- *
- * (i) rt->gcLock held
- */
- static JSBool
- WillDeadlock(JSTitle *title, JSContext *cx)
- {
- JSContext *ownercx;
- do {
- ownercx = title->ownercx;
- if (ownercx == cx) {
- JS_RUNTIME_METER(cx->runtime, deadlocksAvoided);
- return JS_TRUE;
- }
- } while (ownercx && (title = ownercx->titleToShare) != NULL);
- return JS_FALSE;
- }
- /*
- * Make title multi-threaded, i.e. share its ownership among contexts in rt
- * using a "thin" or (if necessary due to contention) "fat" lock. Called only
- * from ClaimTitle, immediately below, when we detect deadlock were we to wait
- * for title's lock, because its ownercx is waiting on a title owned by the
- * calling cx.
- *
- * (i) rt->gcLock held
- */
- static void
- ShareTitle(JSContext *cx, JSTitle *title)
- {
- JSRuntime *rt;
- JSTitle **todop;
- rt = cx->runtime;
- if (title->u.link) {
- for (todop = &rt->titleSharingTodo; *todop != title;
- todop = &(*todop)->u.link) {
- JS_ASSERT(*todop != NO_TITLE_SHARING_TODO);
- }
- *todop = title->u.link;
- title->u.link = NULL; /* null u.link for sanity ASAP */
- JS_NOTIFY_ALL_CONDVAR(rt->titleSharingDone);
- }
- js_InitLock(&title->lock);
- title->u.count = 0;
- js_FinishSharingTitle(cx, title);
- }
- /*
- * js_FinishSharingTitle is the tail part of ShareTitle, split out to become a
- * subroutine of JS_EndRequest too. The bulk of the work here involves making
- * mutable strings in the title's object's slots be immutable. We have to do
- * this because such strings will soon be available to multiple threads, so
- * their buffers can't be realloc'd any longer in js_ConcatStrings, and their
- * members can't be modified by js_ConcatStrings, js_MinimizeDependentStrings,
- * or js_UndependString.
- *
- * The last bit of work done by js_FinishSharingTitle nulls title->ownercx and
- * updates rt->sharedTitles.
- */
- void
- js_FinishSharingTitle(JSContext *cx, JSTitle *title)
- {
- JSObjectMap *map;
- JSScope *scope;
- JSObject *obj;
- uint32 nslots, i;
- jsval v;
- map = TITLE_TO_MAP(title);
- if (!MAP_IS_NATIVE(map))
- return;
- scope = (JSScope *)map;
- obj = scope->object;
- if (obj) {
- nslots = scope->map.freeslot;
- for (i = 0; i != nslots; ++i) {
- v = STOBJ_GET_SLOT(obj, i);
- if (JSVAL_IS_STRING(v) &&
- !js_MakeStringImmutable(cx, JSVAL_TO_STRING(v))) {
- /*
- * FIXME bug 363059: The following error recovery changes
- * runtime execution semantics, arbitrarily and silently
- * ignoring errors except out-of-memory, which should have been
- * reported through JS_ReportOutOfMemory at this point.
- */
- STOBJ_SET_SLOT(obj, i, JSVAL_VOID);
- }
- }
- }
- title->ownercx = NULL; /* NB: set last, after lock init */
- JS_RUNTIME_METER(cx->runtime, sharedTitles);
- }
- /*
- * Given a title with apparently non-null ownercx different from cx, try to
- * set ownercx to cx, claiming exclusive (single-threaded) ownership of title.
- * If we claim ownership, return true. Otherwise, we wait for ownercx to be
- * set to null (indicating that title is multi-threaded); or if waiting would
- * deadlock, we set ownercx to null ourselves via ShareTitle. In any case,
- * once ownercx is null we return false.
- */
- static JSBool
- ClaimTitle(JSTitle *title, JSContext *cx)
- {
- JSRuntime *rt;
- JSContext *ownercx;
- jsrefcount saveDepth;
- PRStatus stat;
- rt = cx->runtime;
- JS_RUNTIME_METER(rt, claimAttempts);
- JS_LOCK_GC(rt);
- /* Reload in case ownercx went away while we blocked on the lock. */
- while ((ownercx = title->ownercx) != NULL) {
- /*
- * Avoid selflock if ownercx is dead, or is not running a request, or
- * has the same thread as cx. Set title->ownercx to cx so that the
- * matching JS_UNLOCK_SCOPE or JS_UNLOCK_OBJ macro call will take the
- * fast path around the corresponding js_UnlockTitle or js_UnlockObj
- * function call.
- *
- * If title->u.link is non-null, title has already been inserted on
- * the rt->titleSharingTodo list, because another thread's context
- * already wanted to lock title while ownercx was running a request.
- * We can't claim any title whose u.link is non-null at this point,
- * even if ownercx->requestDepth is 0 (see below where we suspend our
- * request before waiting on rt->titleSharingDone).
- */
- if (!title->u.link &&
- (!js_ValidContextPointer(rt, ownercx) ||
- !ownercx->requestDepth ||
- ownercx->thread == cx->thread)) {
- JS_ASSERT(title->u.count == 0);
- title->ownercx = cx;
- JS_UNLOCK_GC(rt);
- JS_RUNTIME_METER(rt, claimedTitles);
- return JS_TRUE;
- }
- /*
- * Avoid deadlock if title's owner context is waiting on a title that
- * we own, by revoking title's ownership. This approach to deadlock
- * avoidance works because the engine never nests title locks.
- *
- * If cx could hold locks on ownercx->titleToShare, or if ownercx could
- * hold locks on title, we would need to keep reentrancy counts for all
- * such "flyweight" (ownercx != NULL) locks, so that control would
- * unwind properly once these locks became "thin" or "fat". The engine
- * promotes a title from exclusive to shared access only when locking,
- * never when holding or unlocking.
- *
- * Avoid deadlock before any of this title/context cycle detection if
- * cx is on the active GC's thread, because in that case, no requests
- * will run until the GC completes. Any title wanted by the GC (from
- * a finalizer) that can't be claimed must become shared.
- */
- if (rt->gcThread == cx->thread ||
- (ownercx->titleToShare &&
- WillDeadlock(ownercx->titleToShare, cx))) {
- ShareTitle(cx, title);
- break;
- }
- /*
- * Thanks to the non-zero NO_TITLE_SHARING_TODO link terminator, we
- * can decide whether title is on rt->titleSharingTodo with a single
- * non-null test, and avoid double-insertion bugs.
- */
- if (!title->u.link) {
- title->u.link = rt->titleSharingTodo;
- rt->titleSharingTodo = title;
- js_HoldObjectMap(cx, TITLE_TO_MAP(title));
- }
- /*
- * Inline JS_SuspendRequest before we wait on rt->titleSharingDone,
- * saving and clearing cx->requestDepth so we don't deadlock if the
- * GC needs to run on ownercx.
- *
- * Unlike JS_SuspendRequest and JS_EndRequest, we must take care not
- * to decrement rt->requestCount if cx is active on the GC's thread,
- * because the GC has already reduced rt->requestCount to exclude all
- * such such contexts.
- */
- saveDepth = cx->requestDepth;
- if (saveDepth) {
- cx->requestDepth = 0;
- if (rt->gcThread != cx->thread) {
- JS_ASSERT(rt->requestCount > 0);
- rt->requestCount--;
- if (rt->requestCount == 0)
- JS_NOTIFY_REQUEST_DONE(rt);
- }
- }
- /*
- * We know that some other thread's context owns title, which is now
- * linked onto rt->titleSharingTodo, awaiting the end of that other
- * thread's request. So it is safe to wait on rt->titleSharingDone.
- */
- cx->titleToShare = title;
- stat = PR_WaitCondVar(rt->titleSharingDone, PR_INTERVAL_NO_TIMEOUT);
- JS_ASSERT(stat != PR_FAILURE);
- /*
- * Inline JS_ResumeRequest after waiting on rt->titleSharingDone,
- * restoring cx->requestDepth. Same note as above for the inlined,
- * specialized JS_SuspendRequest code: beware rt->gcThread.
- */
- if (saveDepth) {
- if (rt->gcThread != cx->thread) {
- while (rt->gcLevel > 0)
- JS_AWAIT_GC_DONE(rt);
- rt->requestCount++;
- }
- cx->requestDepth = saveDepth;
- }
- /*
- * Don't clear cx->titleToShare until after we're through waiting on
- * all condition variables protected by rt->gcLock -- that includes
- * rt->titleSharingDone *and* rt->gcDone (hidden in JS_AWAIT_GC_DONE,
- * in the inlined JS_ResumeRequest code immediately above).
- *
- * Otherwise, the GC could easily deadlock with another thread that
- * owns a title wanted by a finalizer. By keeping cx->titleToShare
- * set till here, we ensure that such deadlocks are detected, which
- * results in the finalized object's title being shared (it must, of
- * course, have other, live objects sharing it).
- */
- cx->titleToShare = NULL;
- }
- JS_UNLOCK_GC(rt);
- return JS_FALSE;
- }
- /* Exported to js.c, which calls it via OBJ_GET_* and JSVAL_IS_* macros. */
- JS_FRIEND_API(jsval)
- js_GetSlotThreadSafe(JSContext *cx, JSObject *obj, uint32 slot)
- {
- jsval v;
- JSScope *scope;
- JSTitle *title;
- #ifndef NSPR_LOCK
- JSThinLock *tl;
- jsword me;
- #endif
- /*
- * We handle non-native objects via JSObjectOps.getRequiredSlot, treating
- * all slots starting from 0 as required slots. A property definition or
- * some prior arrangement must have allocated slot.
- *
- * Note once again (see jspubtd.h, before JSGetRequiredSlotOp's typedef)
- * the crucial distinction between a |required slot number| that's passed
- * to the get/setRequiredSlot JSObjectOps, and a |reserved slot index|
- * passed to the JS_Get/SetReservedSlot APIs.
- */
- if (!OBJ_IS_NATIVE(obj))
- return OBJ_GET_REQUIRED_SLOT(cx, obj, slot);
- /*
- * Native object locking is inlined here to optimize the single-threaded
- * and contention-free multi-threaded cases.
- */
- scope = OBJ_SCOPE(obj);
- title = &scope->title;
- JS_ASSERT(title->ownercx != cx);
- JS_ASSERT(slot < obj->map->freeslot);
- /*
- * Avoid locking if called from the GC. Also avoid locking an object
- * owning a sealed scope. If neither of those special cases applies, try
- * to claim scope's flyweight lock from whatever context may have had it in
- * an earlier request.
- */
- if (CX_THREAD_IS_RUNNING_GC(cx) ||
- (SCOPE_IS_SEALED(scope) && scope->object == obj) ||
- (title->ownercx && ClaimTitle(title, cx))) {
- return STOBJ_GET_SLOT(obj, slot);
- }
- #ifndef NSPR_LOCK
- tl = &title->lock;
- me = CX_THINLOCK_ID(cx);
- JS_ASSERT(CURRENT_THREAD_IS_ME(me));
- if (NativeCompareAndSwap(&tl->owner, 0, me)) {
- /*
- * Got the lock with one compare-and-swap. Even so, someone else may
- * have mutated obj so it now has its own scope and lock, which would
- * require either a restart from the top of this routine, or a thin
- * lock release followed by fat lock acquisition.
- */
- if (scope == OBJ_SCOPE(obj)) {
- v = STOBJ_GET_SLOT(obj, slot);
- if (!NativeCompareAndSwap(&tl->owner, me, 0)) {
- /* Assert that scope locks never revert to flyweight. */
- JS_ASSERT(title->ownercx != cx);
- LOGIT(scope, '1');
- title->u.count = 1;
- js_UnlockObj(cx, obj);
- }
- return v;
- }
- if (!NativeCompareAndSwap(&tl->owner, me, 0))
- js_Dequeue(tl);
- }
- else if (Thin_RemoveWait(ReadWord(tl->owner)) == me) {
- return STOBJ_GET_SLOT(obj, slot);
- }
- #endif
- js_LockObj(cx, obj);
- v = STOBJ_GET_SLOT(obj, slot);
- /*
- * Test whether cx took ownership of obj's scope during js_LockObj.
- *
- * This does not mean that a given scope reverted to flyweight from "thin"
- * or "fat" -- it does mean that obj's map pointer changed due to another
- * thread setting a property, requiring obj to cease sharing a prototype
- * object's scope (whose lock was not flyweight, else we wouldn't be here
- * in the first place!).
- */
- title = &OBJ_SCOPE(obj)->title;
- if (title->ownercx != cx)
- js_UnlockTitle(cx, title);
- return v;
- }
- void
- js_SetSlotThreadSafe(JSContext *cx, JSObject *obj, uint32 slot, jsval v)
- {
- JSTitle *title;
- JSScope *scope;
- #ifndef NSPR_LOCK
- JSThinLock *tl;
- jsword me;
- #endif
- /* Any string stored in a thread-safe object must be immutable. */
- if (JSVAL_IS_STRING(v) &&
- !js_MakeStringImmutable(cx, JSVAL_TO_STRING(v))) {
- /* FIXME bug 363059: See comments in js_FinishSharingScope. */
- v = JSVAL_NULL;
- }
- /*
- * We handle non-native objects via JSObjectOps.setRequiredSlot, as above
- * for the Get case.
- */
- if (!OBJ_IS_NATIVE(obj)) {
- OBJ_SET_REQUIRED_SLOT(cx, obj, slot, v);
- return;
- }
- /*
- * Native object locking is inlined here to optimize the single-threaded
- * and contention-free multi-threaded cases.
- */
- scope = OBJ_SCOPE(obj);
- title = &scope->title;
- JS_ASSERT(title->ownercx != cx);
- JS_ASSERT(slot < obj->map->freeslot);
- /*
- * Avoid locking if called from the GC. Also avoid locking an object
- * owning a sealed scope. If neither of those special cases applies, try
- * to claim scope's flyweight lock from whatever context may have had it in
- * an earlier request.
- */
- if (CX_THREAD_IS_RUNNING_GC(cx) ||
- (SCOPE_IS_SEALED(scope) && scope->object == obj) ||
- (title->ownercx && ClaimTitle(title, cx))) {
- LOCKED_OBJ_WRITE_BARRIER(cx, obj, slot, v);
- return;
- }
- #ifndef NSPR_LOCK
- tl = &title->lock;
- me = CX_THINLOCK_ID(cx);
- JS_ASSERT(CURRENT_THREAD_IS_ME(me));
- if (NativeCompareAndSwap(&tl->owner, 0, me)) {
- if (scope == OBJ_SCOPE(obj)) {
- LOCKED_OBJ_WRITE_BARRIER(cx, obj, slot, v);
- if (!NativeCompareAndSwap(&tl->owner, me, 0)) {
- /* Assert that scope locks never revert to flyweight. */
- JS_ASSERT(title->ownercx != cx);
- LOGIT(scope, '1');
- title->u.count = 1;
- js_UnlockObj(cx, obj);
- }
- return;
- }
- if (!NativeCompareAndSwap(&tl->owner, me, 0))
- js_Dequeue(tl);
- }
- else if (Thin_RemoveWait(ReadWord(tl->owner)) == me) {
- LOCKED_OBJ_WRITE_BARRIER(cx, obj, slot, v);
- return;
- }
- #endif
- js_LockObj(cx, obj);
- LOCKED_OBJ_WRITE_BARRIER(cx, obj, slot, v);
- /*
- * Same drill as above, in js_GetSlotThreadSafe.
- */
- title = &OBJ_SCOPE(obj)->title;
- if (title->ownercx != cx)
- js_UnlockTitle(cx, title);
- }
- #ifndef NSPR_LOCK
- static JSFatLock *
- NewFatlock()
- {
- JSFatLock *fl = (JSFatLock *)malloc(sizeof(JSFatLock)); /* for now */
- if (!fl) return NULL;
- fl->susp = 0;
- fl->next = NULL;
- fl->prevp = NULL;
- fl->slock = PR_NewLock();
- fl->svar = PR_NewCondVar(fl->slock);
- return fl;
- }
- static void
- DestroyFatlock(JSFatLock *fl)
- {
- PR_DestroyLock(fl->slock);
- PR_DestroyCondVar(fl->svar);
- free(fl);
- }
- static JSFatLock *
- ListOfFatlocks(int listc)
- {
- JSFatLock *m;
- JSFatLock *m0;
- int i;
- JS_ASSERT(listc>0);
- m0 = m = NewFatlock();
- for (i=1; i<listc; i++) {
- m->next = NewFatlock();
- m = m->next;
- }
- return m0;
- }
- static void
- DeleteListOfFatlocks(JSFatLock *m)
- {
- JSFatLock *m0;
- for (; m; m=m0) {
- m0 = m->next;
- DestroyFatlock(m);
- }
- }
- static JSFatLockTable *fl_list_table = NULL;
- static uint32 fl_list_table_len = 0;
- static uint32 fl_list_chunk_len = 0;
- static JSFatLock *
- GetFatlock(void *id)
- {
- JSFatLock *m;
- uint32 i = GLOBAL_LOCK_INDEX(id);
- if (fl_list_table[i].free == NULL) {
- #ifdef DEBUG
- if (fl_list_table[i].taken)
- printf("Ran out of fat locks!\n");
- #endif
- fl_list_table[i].free = ListOfFatlocks(fl_list_chunk_len);
- }
- m = fl_list_table[i].free;
- fl_list_table[i].free = m->next;
- m->susp = 0;
- m->next = fl_list_table[i].taken;
- m->prevp = &fl_list_table[i].taken;
- if (fl_list_table[i].taken)
- fl_list_table[i].taken->prevp = &m->next;
- fl_list_table[i].taken = m;
- return m;
- }
- static void
- PutFatlock(JSFatLock *m, void *id)
- {
- uint32 i;
- if (m == NULL)
- return;
- /* Unlink m from fl_list_table[i].taken. */
- *m->prevp = m->next;
- if (m->next)
- m->next->prevp = m->prevp;
- /* Insert m in fl_list_table[i].free. */
- i = GLOBAL_LOCK_INDEX(id);
- m->next = fl_list_table[i].free;
- fl_list_table[i].free = m;
- }
- #endif /* !NSPR_LOCK */
- JSBool
- js_SetupLocks(int listc, int globc)
- {
- #ifndef NSPR_LOCK
- uint32 i;
- if (global_locks)
- return JS_TRUE;
- #ifdef DEBUG
- if (listc > 10000 || listc < 0) /* listc == fat lock list chunk length */
- printf("Bad number %d in js_SetupLocks()!\n", listc);
- if (globc > 100 || globc < 0) /* globc == number of global locks */
- printf("Bad number %d in js_SetupLocks()!\n", listc);
- #endif
- global_locks_log2 = JS_CeilingLog2(globc);
- global_locks_mask = JS_BITMASK(global_locks_log2);
- global_lock_count = JS_BIT(global_locks_log2);
- global_locks = (PRLock **) malloc(global_lock_count * sizeof(PRLock*));
- if (!global_locks)
- return JS_FALSE;
- for (i = 0; i < global_lock_count; i++) {
- global_locks[i] = PR_NewLock();
- if (!global_locks[i]) {
- global_lock_count = i;
- js_CleanupLocks();
- return JS_FALSE;
- }
- }
- fl_list_table = (JSFatLockTable *) malloc(i * sizeof(JSFatLockTable));
- if (!fl_list_table) {
- js_CleanupLocks();
- return JS_FALSE;
- }
- fl_list_table_len = global_lock_count;
- for (i = 0; i < global_lock_count; i++)
- fl_list_table[i].free = fl_list_table[i].taken = NULL;
- fl_list_chunk_len = listc;
- #endif /* !NSPR_LOCK */
- return JS_TRUE;
- }
- void
- js_CleanupLocks()
- {
- #ifndef NSPR_LOCK
- uint32 i;
- if (global_locks) {
- for (i = 0; i < global_lock_count; i++)
- PR_DestroyLock(global_locks[i]);
- free(global_locks);
- global_locks = NULL;
- global_lock_count = 1;
- global_locks_log2 = 0;
- global_locks_mask = 0;
- }
- if (fl_list_table) {
- for (i = 0; i < fl_list_table_len; i++) {
- DeleteListOfFatlocks(fl_list_table[i].free);
- fl_list_table[i].free = NULL;
- DeleteListOfFatlocks(fl_list_table[i].taken);
- fl_list_table[i].taken = NULL;
- }
- free(fl_list_table);
- fl_list_table = NULL;
- fl_list_table_len = 0;
- }
- #endif /* !NSPR_LOCK */
- }
- #ifdef NSPR_LOCK
- static JS_ALWAYS_INLINE void
- ThinLock(JSThinLock *tl, jsword me)
- {
- JS_ACQUIRE_LOCK((JSLock *) tl->fat);
- tl->owner = me;
- }
- static JS_ALWAYS_INLINE void
- ThinUnlock(JSThinLock *tl, jsword /*me*/)
- {
- tl->owner = 0;
- JS_RELEASE_LOCK((JSLock *) tl->fat);
- }
- #else
- /*
- * Fast locking and unlocking is implemented by delaying the allocation of a
- * system lock (fat lock) until contention. As long as a locking thread A
- * runs uncontended, the lock is represented solely by storing A's identity in
- * the object being locked.
- *
- * If another thread B tries to lock the object currently locked by A, B is
- * enqueued into a fat lock structure (which might have to be allocated and
- * pointed to by the object), and suspended using NSPR conditional variables
- * (wait). A wait bit (Bacon bit) is set in the lock word of the object,
- * signalling to A that when releasing the lock, B must be dequeued and
- * notified.
- *
- * The basic operation of the locking primitives (js_Lock, js_Unlock,
- * js_Enqueue, and js_Dequeue) is compare-and-swap. Hence, when locking into
- * the word pointed at by p, compare-and-swap(p, 0, A) success implies that p
- * is unlocked. Similarly, when unlocking p, if compare-and-swap(p, A, 0)
- * succeeds this implies that p is uncontended (no one is waiting because the
- * wait bit is not set).
- *
- * When dequeueing, the lock is released, and one of the threads suspended on
- * the lock is notified. If other threads still are waiting, the wait bit is
- * kept (in js_Enqueue), and if not, the fat lock is deallocated.
- *
- * The functions js_Enqueue, js_Dequeue, js_SuspendThread, and js_ResumeThread
- * are serialized using a global lock. For scalability, a hashtable of global
- * locks is used, which is indexed modulo the thin lock pointer.
- */
- /*
- * Invariants:
- * (i) global lock is held
- * (ii) fl->susp >= 0
- */
- static int
- js_SuspendThread(JSThinLock *tl)
- {
- JSFatLock *fl;
- PRStatus stat;
- if (tl->fat == NULL)
- fl = tl->fat = GetFatlock(tl);
- else
- fl = tl->fat;
- JS_ASSERT(fl->susp >= 0);
- fl->susp++;
- PR_Lock(fl->slock);
- js_UnlockGlobal(tl);
- stat = PR_WaitCondVar(fl->svar, PR_INTERVAL_NO_TIMEOUT);
- JS_ASSERT(stat != PR_FAILURE);
- PR_Unlock(fl->slock);
- js_LockGlobal(tl);
- fl->susp--;
- if (fl->susp == 0) {
- PutFatlock(fl, tl);
- tl->fat = NULL;
- }
- return tl->fat == NULL;
- }
- /*
- * (i) global lock is held
- * (ii) fl->susp > 0
- */
- static void
- js_ResumeThread(JSThinLock *tl)
- {
- JSFatLock *fl = tl->fat;
- PRStatus stat;
- JS_ASSERT(fl != NULL);
- JS_ASSERT(fl->susp > 0);
- PR_Lock(fl->slock);
- js_UnlockGlobal(tl);
- stat = PR_NotifyCondVar(fl->svar);
- JS_ASSERT(stat != PR_FAILURE);
- PR_Unlock(fl->slock);
- }
- static void
- js_Enqueue(JSThinLock *tl, jsword me)
- {
- jsword o, n;
- js_LockGlobal(tl);
- for (;;) {
- o = ReadWord(tl->owner);
- n = Thin_SetWait(o);
- if (o != 0 && NativeCompareAndSwap(&tl->owner, o, n)) {
- if (js_SuspendThread(tl))
- me = Thin_RemoveWait(me);
- else
- me = Thin_SetWait(me);
- }
- else if (NativeCompareAndSwap(&tl->owner, 0, me)) {
- js_UnlockGlobal(tl);
- return;
- }
- }
- }
- static void
- js_Dequeue(JSThinLock *tl)
- {
- jsword o;
- js_LockGlobal(tl);
- o = ReadWord(tl->owner);
- JS_ASSERT(Thin_GetWait(o) != 0);
- JS_ASSERT(tl->fat != NULL);
- if (!NativeCompareAndSwap(&tl->owner, o, 0)) /* release it */
- JS_ASSERT(0);
- js_ResumeThread(tl);
- }
- static JS_ALWAYS_INLINE void
- ThinLock(JSThinLock *tl, jsword me)
- {
- JS_ASSERT(CURRENT_THREAD_IS_ME(me));
- if (NativeCompareAndSwap(&tl->owner, 0, me))
- return;
- if (Thin_RemoveWait(ReadWord(tl->owner)) != me)
- js_Enqueue(tl, me);
- #ifdef DEBUG
- else
- JS_ASSERT(0);
- #endif
- }
- static JS_ALWAYS_INLINE void
- ThinUnlock(JSThinLock *tl, jsword me)
- {
- JS_ASSERT(CURRENT_THREAD_IS_ME(me));
- /*
- * Since we can race with the NativeCompareAndSwap in js_Enqueue, we need
- * to use a C_A_S here as well -- Arjan van de Ven 30/1/08
- */
- if (NativeCompareAndSwap(&tl->owner, me, 0))
- return;
- JS_ASSERT(Thin_GetWait(tl->owner));
- if (Thin_RemoveWait(ReadWord(tl->owner)) == me)
- js_Dequeue(tl);
- #ifdef DEBUG
- else
- JS_ASSERT(0); /* unbalanced unlock */
- #endif
- }
- #endif /* !NSPR_LOCK */
- void
- js_Lock(JSContext *cx, JSThinLock *tl)
- {
- ThinLock(tl, CX_THINLOCK_ID(cx));
- }
- void
- js_Unlock(JSContext *cx, JSThinLock *tl)
- {
- ThinUnlock(tl, CX_THINLOCK_ID(cx));
- }
- void
- js_LockRuntime(JSRuntime *rt)
- {
- PR_Lock(rt->rtLock);
- #ifdef DEBUG
- rt->rtLockOwner = js_CurrentThreadId();
- #endif
- }
- void
- js_UnlockRuntime(JSRuntime *rt)
- {
- #ifdef DEBUG
- rt->rtLockOwner = 0;
- #endif
- PR_Unlock(rt->rtLock);
- }
- void
- js_LockTitle(JSContext *cx, JSTitle *title)
- {
- jsword me = CX_THINLOCK_ID(cx);
- JS_ASSERT(CURRENT_THREAD_IS_ME(me));
- JS_ASSERT(title->ownercx != cx);
- if (CX_THREAD_IS_RUNNING_GC(cx))
- return;
- if (title->ownercx && ClaimTitle(title, cx))
- return;
- if (Thin_RemoveWait(ReadWord(title->lock.owner)) == me) {
- JS_ASSERT(title->u.count > 0);
- LOGIT(scope, '+');
- title->u.count++;
- } else {
- ThinLock(&title->lock, me);
- JS_ASSERT(title->u.count == 0);
- LOGIT(scope, '1');
- title->u.count = 1;
- }
- }
- void
- js_UnlockTitle(JSContext *cx, JSTitle *title)
- {
- jsword me = CX_THINLOCK_ID(cx);
- /* We hope compilers use me instead of reloading cx->thread in the macro. */
- if (CX_THREAD_IS_RUNNING_GC(cx))
- return;
- if (cx->lockedSealedTitle == title) {
- cx->lockedSealedTitle = NULL;
- return;
- }
- /*
- * If title->ownercx is not null, it's likely that two contexts not using
- * requests nested locks for title. The first context, cx here, claimed
- * title; the second, title->ownercx here, re-claimed it because the first
- * was not in a request, or was on the same thread. We don't want to keep
- * track of such nesting, because it penalizes the common non-nested case.
- * Instead of asserting here and silently coping, we simply re-claim title
- * for cx and return.
- *
- * See http://bugzilla.mozilla.org/show_bug.cgi?id=229200 for a real world
- * case where an asymmetric thread model (Mozilla's main thread is known
- * to be the only thread that runs the GC) combined with multiple contexts
- * per thread has led to such request-less nesting.
- */
- if (title->ownercx) {
- JS_ASSERT(title->u.count == 0);
- JS_ASSERT(title->lock.owner == 0);
- title->ownercx = cx;
- return;
- }
- JS_ASSERT(title->u.count > 0);
- if (Thin_RemoveWait(ReadWord(title->lock.owner)) != me) {
- JS_ASSERT(0); /* unbalanced unlock */
- return;
- }
- LOGIT(scope, '-');
- if (--title->u.count == 0)
- ThinUnlock(&title->lock, me);
- }
- /*
- * NB: oldtitle may be null if our caller is js_GetMutableScope and it just
- * dropped the last reference to oldtitle.
- */
- void
- js_TransferTitle(JSContext *cx, JSTitle *oldtitle, JSTitle *newtitle)
- {
- JS_ASSERT(JS_IS_TITLE_LOCKED(cx, newtitle));
- /*
- * If the last reference to oldtitle went away, newtitle needs no lock
- * state update.
- */
- if (!oldtitle)
- return;
- JS_ASSERT(JS_IS_TITLE_LOCKED(cx, oldtitle));
- /*
- * Special case in js_LockTitle and js_UnlockTitle for the GC calling
- * code that locks, unlocks, or mutates. Nothing to do in these cases,
- * because title and newtitle were "locked" by the GC thread, so neither
- * was actually locked.
- */
- if (CX_THREAD_IS_RUNNING_GC(cx))
- return;
- /*
- * Special case in js_LockObj and js_UnlockTitle for locking the sealed
- * scope of an object that owns that scope (the prototype or mutated obj
- * for which OBJ_SCOPE(obj)->object == obj), and unlocking it.
- */
- JS_ASSERT(cx->lockedSealedTitle != newtitle);
- if (cx->lockedSealedTitle == oldtitle) {
- JS_ASSERT(newtitle->ownercx == cx ||
- (!newtitle->ownercx && newtitle->u.count == 1));
- cx->lockedSealedTitle = NULL;
- return;
- }
- /*
- * If oldtitle is single-threaded, there's nothing to do.
- */
- if (oldtitle->ownercx) {
- JS_ASSERT(oldtitle->ownercx == cx);
- JS_ASSERT(newtitle->ownercx == cx ||
- (!newtitle->ownercx && newtitle->u.count == 1));
- return;
- }
- /*
- * We transfer oldtitle->u.count only if newtitle is not single-threaded.
- * Flow unwinds from here through some number of JS_UNLOCK_TITLE and/or
- * JS_UNLOCK_OBJ macro calls, which will decrement newtitle->u.count only
- * if they find newtitle->ownercx != cx.
- */
- if (newtitle->ownercx != cx) {
- JS_ASSERT(!newtitle->ownercx);
- newtitle->u.count = oldtitle->u.count;
- }
- /*
- * Reset oldtitle's lock state so that it is completely unlocked.
- */
- LOGIT(oldscope, '0');
- oldtitle->u.count = 0;
- ThinUnlock(&oldtitle->lock, CX_THINLOCK_ID(cx));
- }
- void
- js_LockObj(JSContext *cx, JSObject *obj)
- {
- JSScope *scope;
- JSTitle *title;
- JS_ASSERT(OBJ_IS_NATIVE(obj));
- /*
- * We must test whether the GC is calling and return without mutating any
- * state, especially cx->lockedSealedScope. Note asymmetry with respect to
- * js_UnlockObj, which is a thin-layer on top of js_UnlockTitle.
- */
- if (CX_THREAD_IS_RUNNING_GC(cx))
- return;
- for (;;) {
- scope = OBJ_SCOPE(obj);
- title = &scope->title;
- if (SCOPE_IS_SEALED(scope) && scope->object == obj &&
- !cx->lockedSealedTitle) {
- cx->lockedSealedTitle = title;
- return;
- }
- js_LockTitle(cx, title);
- /* If obj still has this scope, we're done. */
- if (scope == OBJ_SCOPE(obj))
- return;
- /* Lost a race with a mutator; retry with obj's new scope. */
- js_UnlockTitle(cx, title);
- }
- }
- void
- js_UnlockObj(JSContext *cx, JSObject *obj)
- {
- JS_ASSERT(OBJ_IS_NATIVE(obj));
- js_UnlockTitle(cx, &OBJ_SCOPE(obj)->title);
- }
- void
- js_InitTitle(JSContext *cx, JSTitle *title)
- {
- #ifdef JS_THREADSAFE
- title->ownercx = cx;
- memset(&title->lock, 0, sizeof title->lock);
- /*
- * Set u.link = NULL, not u.count = 0, in case the target architecture's
- * null pointer has a non-zero integer representation.
- */
- title->u.link = NULL;
- #ifdef JS_DEBUG_TITLE_LOCKS
- title->file[0] = title->file[1] = title->file[2] = title->file[3] = NULL;
- title->line[0] = title->line[1] = title->line[2] = title->line[3] = 0;
- #endif
- #endif
- }
- void
- js_FinishTitle(JSContext *cx, JSTitle *title)
- {
- #ifdef JS_THREADSAFE
- /* Title must be single-threaded at this point, so set ownercx. */
- JS_ASSERT(title->u.count == 0);
- title->ownercx = cx;
- js_FinishLock(&title->lock);
- #endif
- }
- #ifdef DEBUG
- JSBool
- js_IsRuntimeLocked(JSRuntime *rt)
- {
- return js_CurrentThreadId() == rt->rtLockOwner;
- }
- JSBool
- js_IsObjLocked(JSContext *cx, JSObject *obj)
- {
- JSScope *scope = OBJ_SCOPE(obj);
- return MAP_IS_NATIVE(&scope->map) && js_IsTitleLocked(cx, &scope->title);
- }
- JSBool
- js_IsTitleLocked(JSContext *cx, JSTitle *title)
- {
- /* Special case: the GC locking any object's title, see js_LockTitle. */
- if (CX_THREAD_IS_RUNNING_GC(cx))
- return JS_TRUE;
- /* Special case: locked object owning a sealed scope, see js_LockObj. */
- if (cx->lockedSealedTitle == title)
- return JS_TRUE;
- /*
- * General case: the title is either exclusively owned (by cx), or it has
- * a thin or fat lock to cope with shared (concurrent) ownership.
- */
- if (title->ownercx) {
- JS_ASSERT(title->ownercx == cx || title->ownercx->thread == cx->thread);
- return JS_TRUE;
- }
- return js_CurrentThreadId() ==
- ((JSThread *)Thin_RemoveWait(ReadWord(title->lock.owner)))->id;
- }
- #ifdef JS_DEBUG_TITLE_LOCKS
- void
- js_SetScopeInfo(JSScope *scope, const char *file, int line)
- {
- JSTitle *title = &scope->title;
- if (!title->ownercx) {
- jsrefcount count = title->u.count;
- JS_ASSERT_IF(!SCOPE_IS_SEALED(scope), count > 0);
- JS_ASSERT(count <= 4);
- title->file[count - 1] = file;
- title->line[count - 1] = line;
- }
- }
- #endif /* JS_DEBUG_TITLE_LOCKS */
- #endif /* DEBUG */
- #endif /* JS_THREADSAFE */