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freeswitch/libs/js/src/jsgc.c

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add js to tree git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@3693 d0543943-73ff-0310-b7d9-9358b9ac24b2
2006-12-18 15:53:47 +00:00
/* -*- 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 ***** */
/*
* JS Mark-and-Sweep Garbage Collector.
*
* This GC allocates only fixed-sized things big enough to contain two words
* (pointers) on any host architecture. It allocates from an arena pool (see
* jsarena.h). It uses an ideally parallel array of flag bytes to hold the
* mark bit, finalizer type index, etc.
*
* XXX swizzle page to freelist for better locality of reference
*/
#include "jsstddef.h"
#include <stdlib.h> /* for free, called by JS_ARENA_DESTROY */
#include <string.h> /* for memset, called by jsarena.h macros if DEBUG */
#include "jstypes.h"
#include "jsarena.h" /* Added by JSIFY */
#include "jsutil.h" /* Added by JSIFY */
#include "jshash.h" /* Added by JSIFY */
#include "jsapi.h"
#include "jsatom.h"
#include "jscntxt.h"
#include "jsconfig.h"
#include "jsdbgapi.h"
#include "jsfun.h"
#include "jsgc.h"
#include "jsinterp.h"
#include "jslock.h"
#include "jsnum.h"
#include "jsobj.h"
#include "jsscope.h"
#include "jsscript.h"
#include "jsstr.h"
#if JS_HAS_XML_SUPPORT
#include "jsxml.h"
#endif
/*
* GC arena sizing depends on amortizing arena overhead using a large number
* of things per arena, and on the thing/flags ratio of 8:1 on most platforms.
*
* On 64-bit platforms, we would have half as many things per arena because
* pointers are twice as big, so we double the bytes for things per arena.
* This preserves the 1024 byte flags sub-arena size, which relates to the
* GC_PAGE_SIZE (see below for why).
*/
#if JS_BYTES_PER_WORD == 8
# define GC_THINGS_SHIFT 14 /* 16KB for things on Alpha, etc. */
#else
# define GC_THINGS_SHIFT 13 /* 8KB for things on most platforms */
#endif
#define GC_THINGS_SIZE JS_BIT(GC_THINGS_SHIFT)
#define GC_FLAGS_SIZE (GC_THINGS_SIZE / sizeof(JSGCThing))
#define GC_ARENA_SIZE (GC_THINGS_SIZE + GC_FLAGS_SIZE)
/*
* A GC arena contains one flag byte for each thing in its heap, and supports
* O(1) lookup of a flag given its thing's address.
*
* To implement this, we take advantage of the thing/flags numerology: given
* the 8K bytes worth of GC-things, there are 1K flag bytes. We mask a thing's
* address with ~1023 to find a JSGCPageInfo record at the front of a mythical
* "GC page" within the larger 8K thing arena. That JSGCPageInfo contains a
* pointer to the 128 flag bytes corresponding to the things in the page, so we
* index into this flags array using the thing's index within its page.
*
* To align thing pages on 1024-byte boundaries, we must allocate the 9KB of
* flags+things arena payload, then find the first 0 mod 1024 boundary after
* the first payload address. That's where things start, with a JSGCPageInfo
* taking up the first thing-slot, as usual for 0 mod 1024 byte boundaries.
* The effect of this alignment trick is to split the flags into at most 2
* discontiguous spans, one before the things and one after (if we're really
* lucky, and the arena payload starts on a 0 mod 1024 byte boundary, no need
* to split).
*
* The overhead of this scheme for most platforms is (16+8*(8+1))/(16+9K) or
* .95% (assuming 16 byte JSArena header size, and 8 byte JSGCThing size).
*
* Here's some ASCII art showing an arena:
*
* split
* |
* V
* +--+-------+-------+-------+-------+-------+-------+-------+-------+-----+
* |fB| tp0 | tp1 | tp2 | tp3 | tp4 | tp5 | tp6 | tp7 | fA |
* +--+-------+-------+-------+-------+-------+-------+-------+-------+-----+
* ^ ^
* tI ---------+ |
* tJ -------------------------------------------+
*
* - fB are the "before split" flags, fA are the "after split" flags
* - tp0-tp7 are the 8 thing pages
* - thing tI points into tp1, whose flags are below the split, in fB
* - thing tJ points into tp5, clearly above the split
*
* In general, one of the thing pages will have some of its things' flags on
* the low side of the split, and the rest of its things' flags on the high
* side. All the other pages have flags only below or only above. Therefore
* we'll have to test something to decide whether the split divides flags in
* a given thing's page. So we store the split pointer (the pointer to tp0)
* in each JSGCPageInfo, along with the flags pointer for the 128 flag bytes
* ideally starting, for tp0 things, at the beginning of the arena's payload
* (at the start of fB).
*
* That is, each JSGCPageInfo's flags pointer is 128 bytes from the previous,
* or at the start of the arena if there is no previous page in this arena.
* Thus these ideal 128-byte flag pages run contiguously from the start of the
* arena (right over the split!), and the JSGCPageInfo flags pointers contain
* no discontinuities over the split created by the thing pages. So if, for a
* given JSGCPageInfo *pi, we find that
*
* pi->flags + ((jsuword)thing % 1024) / sizeof(JSGCThing) >= pi->split
*
* then we must add GC_THINGS_SIZE to the nominal flags pointer to jump over
* all the thing pages that split the flags into two discontiguous spans.
*
* (If we need to implement card-marking for an incremental GC write barrier,
* we can use the low byte of the pi->split pointer as the card-mark, for an
* extremely efficient write barrier: when mutating an object obj, just store
* a 1 byte at (uint8 *) ((jsuword)obj & ~1023) for little-endian platforms.
* When finding flags, we'll of course have to mask split with ~255, but it is
* guaranteed to be 1024-byte aligned, so no information is lost by overlaying
* the card-mark byte on split's low byte.)
*/
#define GC_PAGE_SHIFT 10
#define GC_PAGE_MASK ((jsuword) JS_BITMASK(GC_PAGE_SHIFT))
#define GC_PAGE_SIZE JS_BIT(GC_PAGE_SHIFT)
typedef struct JSGCPageInfo {
uint8 *split;
uint8 *flags;
} JSGCPageInfo;
#define FIRST_THING_PAGE(a) (((a)->base + GC_FLAGS_SIZE) & ~GC_PAGE_MASK)
/*
* Given a jsuword page pointer p and a thing size n, return the address of
* the first thing in p. We know that any n not a power of two packs from
* the end of the page leaving at least enough room for one JSGCPageInfo, but
* not for another thing, at the front of the page (JS_ASSERTs below insist
* on this).
*
* This works because all allocations are a multiple of sizeof(JSGCThing) ==
* sizeof(JSGCPageInfo) in size.
*/
#define FIRST_THING(p,n) (((n) & ((n) - 1)) \
? (p) + (uint32)(GC_PAGE_SIZE % (n)) \
: (p) + (n))
static JSGCThing *
gc_new_arena(JSArenaPool *pool, size_t nbytes)
{
uint8 *flagp, *split, *pagep, *limit;
JSArena *a;
jsuword p;
JSGCThing *thing;
JSGCPageInfo *pi;
/* Use JS_ArenaAllocate to grab another 9K-net-size hunk of space. */
flagp = (uint8 *) JS_ArenaAllocate(pool, GC_ARENA_SIZE);
if (!flagp)
return NULL;
a = pool->current;
/* Reset a->avail to start at the flags split, aka the first thing page. */
p = FIRST_THING_PAGE(a);
split = pagep = (uint8 *) p;
a->avail = FIRST_THING(p, nbytes);
JS_ASSERT(a->avail >= p + sizeof(JSGCPageInfo));
thing = (JSGCThing *) a->avail;
JS_ArenaCountAllocation(pool, a->avail - p);
a->avail += nbytes;
/* Initialize the JSGCPageInfo records at the start of every thing page. */
limit = pagep + GC_THINGS_SIZE;
do {
pi = (JSGCPageInfo *) pagep;
pi->split = split;
pi->flags = flagp;
flagp += GC_PAGE_SIZE >> (GC_THINGS_SHIFT - GC_PAGE_SHIFT);
pagep += GC_PAGE_SIZE;
} while (pagep < limit);
return thing;
}
uint8 *
js_GetGCThingFlags(void *thing)
{
JSGCPageInfo *pi;
uint8 *flagp;
pi = (JSGCPageInfo *) ((jsuword)thing & ~GC_PAGE_MASK);
flagp = pi->flags + ((jsuword)thing & GC_PAGE_MASK) / sizeof(JSGCThing);
if (flagp >= pi->split)
flagp += GC_THINGS_SIZE;
return flagp;
}
JSBool
js_IsAboutToBeFinalized(JSContext *cx, void *thing)
{
uint8 flags = *js_GetGCThingFlags(thing);
return !(flags & (GCF_MARK | GCF_LOCK | GCF_FINAL));
}
typedef void (*GCFinalizeOp)(JSContext *cx, JSGCThing *thing);
#ifndef DEBUG
# define js_FinalizeDouble NULL
#endif
#if !JS_HAS_XML_SUPPORT
# define js_FinalizeXMLNamespace NULL
# define js_FinalizeXMLQName NULL
# define js_FinalizeXML NULL
#endif
static GCFinalizeOp gc_finalizers[GCX_NTYPES] = {
(GCFinalizeOp) js_FinalizeObject, /* GCX_OBJECT */
(GCFinalizeOp) js_FinalizeString, /* GCX_STRING */
(GCFinalizeOp) js_FinalizeDouble, /* GCX_DOUBLE */
(GCFinalizeOp) js_FinalizeString, /* GCX_MUTABLE_STRING */
NULL, /* GCX_PRIVATE */
(GCFinalizeOp) js_FinalizeXMLNamespace, /* GCX_NAMESPACE */
(GCFinalizeOp) js_FinalizeXMLQName, /* GCX_QNAME */
(GCFinalizeOp) js_FinalizeXML, /* GCX_XML */
NULL, /* GCX_EXTERNAL_STRING */
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL
};
#ifdef GC_MARK_DEBUG
static const char newborn_external_string[] = "newborn external string";
static const char *gc_typenames[GCX_NTYPES] = {
"newborn object",
"newborn string",
"newborn double",
"newborn mutable string",
"newborn private",
"newborn Namespace",
"newborn QName",
"newborn XML",
newborn_external_string,
newborn_external_string,
newborn_external_string,
newborn_external_string,
newborn_external_string,
newborn_external_string,
newborn_external_string,
newborn_external_string
};
#endif
intN
js_ChangeExternalStringFinalizer(JSStringFinalizeOp oldop,
JSStringFinalizeOp newop)
{
uintN i;
for (i = GCX_EXTERNAL_STRING; i < GCX_NTYPES; i++) {
if (gc_finalizers[i] == (GCFinalizeOp) oldop) {
gc_finalizers[i] = (GCFinalizeOp) newop;
return (intN) i;
}
}
return -1;
}
#ifdef JS_GCMETER
#define METER(x) x
#else
#define METER(x) /* nothing */
#endif
/* Initial size of the gcRootsHash table (SWAG, small enough to amortize). */
#define GC_ROOTS_SIZE 256
#define GC_FINALIZE_LEN 1024
JSBool
js_InitGC(JSRuntime *rt, uint32 maxbytes)
{
uintN i;
JS_ASSERT(sizeof(JSGCThing) == sizeof(JSGCPageInfo));
JS_ASSERT(sizeof(JSGCThing) >= sizeof(JSObject));
JS_ASSERT(sizeof(JSGCThing) >= sizeof(JSString));
JS_ASSERT(sizeof(JSGCThing) >= sizeof(jsdouble));
JS_ASSERT(GC_FLAGS_SIZE >= GC_PAGE_SIZE);
JS_ASSERT(sizeof(JSStackHeader) >= 2 * sizeof(jsval));
for (i = 0; i < GC_NUM_FREELISTS; i++)
JS_InitArenaPool(&rt->gcArenaPool[i], "gc-arena", GC_ARENA_SIZE, 1);
if (!JS_DHashTableInit(&rt->gcRootsHash, JS_DHashGetStubOps(), NULL,
sizeof(JSGCRootHashEntry), GC_ROOTS_SIZE)) {
rt->gcRootsHash.ops = NULL;
return JS_FALSE;
}
rt->gcLocksHash = NULL; /* create lazily */
rt->gcMaxBytes = maxbytes;
return JS_TRUE;
}
#ifdef JS_GCMETER
JS_FRIEND_API(void)
js_DumpGCStats(JSRuntime *rt, FILE *fp)
{
uintN i;
fprintf(fp, "\nGC allocation statistics:\n");
#define UL(x) ((unsigned long)(x))
#define ULSTAT(x) UL(rt->gcStats.x)
fprintf(fp, " public bytes allocated: %lu\n", UL(rt->gcBytes));
fprintf(fp, " private bytes allocated: %lu\n", UL(rt->gcPrivateBytes));
fprintf(fp, " alloc attempts: %lu\n", ULSTAT(alloc));
for (i = 0; i < GC_NUM_FREELISTS; i++) {
fprintf(fp, " GC freelist %u length: %lu\n",
i, ULSTAT(freelen[i]));
fprintf(fp, " recycles via GC freelist %u: %lu\n",
i, ULSTAT(recycle[i]));
}
fprintf(fp, "allocation retries after GC: %lu\n", ULSTAT(retry));
fprintf(fp, " allocation failures: %lu\n", ULSTAT(fail));
fprintf(fp, " things born locked: %lu\n", ULSTAT(lockborn));
fprintf(fp, " valid lock calls: %lu\n", ULSTAT(lock));
fprintf(fp, " valid unlock calls: %lu\n", ULSTAT(unlock));
fprintf(fp, " mark recursion depth: %lu\n", ULSTAT(depth));
fprintf(fp, " maximum mark recursion: %lu\n", ULSTAT(maxdepth));
fprintf(fp, " mark C recursion depth: %lu\n", ULSTAT(cdepth));
fprintf(fp, " maximum mark C recursion: %lu\n", ULSTAT(maxcdepth));
fprintf(fp, " mark C stack overflows: %lu\n", ULSTAT(dswmark));
fprintf(fp, " mark DSW recursion depth: %lu\n", ULSTAT(dswdepth));
fprintf(fp, " maximum mark DSW recursion: %lu\n", ULSTAT(maxdswdepth));
fprintf(fp, " mark DSW up-tree movement: %lu\n", ULSTAT(dswup));
fprintf(fp, "DSW up-tree obj->slot steps: %lu\n", ULSTAT(dswupstep));
fprintf(fp, " maximum GC nesting level: %lu\n", ULSTAT(maxlevel));
fprintf(fp, "potentially useful GC calls: %lu\n", ULSTAT(poke));
fprintf(fp, " useless GC calls: %lu\n", ULSTAT(nopoke));
fprintf(fp, " thing arenas freed so far: %lu\n", ULSTAT(afree));
fprintf(fp, " stack segments scanned: %lu\n", ULSTAT(stackseg));
fprintf(fp, "stack segment slots scanned: %lu\n", ULSTAT(segslots));
#undef UL
#undef US
#ifdef JS_ARENAMETER
JS_DumpArenaStats(fp);
#endif
}
#endif
#ifdef DEBUG
JS_STATIC_DLL_CALLBACK(JSDHashOperator)
js_root_printer(JSDHashTable *table, JSDHashEntryHdr *hdr, uint32 i, void *arg)
{
uint32 *leakedroots = (uint32 *)arg;
JSGCRootHashEntry *rhe = (JSGCRootHashEntry *)hdr;
(*leakedroots)++;
fprintf(stderr,
"JS engine warning: leaking GC root \'%s\' at %p\n",
rhe->name ? (char *)rhe->name : "", rhe->root);
return JS_DHASH_NEXT;
}
#endif
void
js_FinishGC(JSRuntime *rt)
{
uintN i;
#ifdef JS_ARENAMETER
JS_DumpArenaStats(stdout);
#endif
#ifdef JS_GCMETER
js_DumpGCStats(rt, stdout);
#endif
for (i = 0; i < GC_NUM_FREELISTS; i++) {
JS_FinishArenaPool(&rt->gcArenaPool[i]);
rt->gcFreeList[i] = NULL;
}
JS_ArenaFinish();
if (rt->gcRootsHash.ops) {
#ifdef DEBUG
uint32 leakedroots = 0;
/* Warn (but don't assert) debug builds of any remaining roots. */
JS_DHashTableEnumerate(&rt->gcRootsHash, js_root_printer,
&leakedroots);
if (leakedroots > 0) {
if (leakedroots == 1) {
fprintf(stderr,
"JS engine warning: 1 GC root remains after destroying the JSRuntime.\n"
" This root may point to freed memory. Objects reachable\n"
" through it have not been finalized.\n");
} else {
fprintf(stderr,
"JS engine warning: %lu GC roots remain after destroying the JSRuntime.\n"
" These roots may point to freed memory. Objects reachable\n"
" through them have not been finalized.\n",
(unsigned long) leakedroots);
}
}
#endif
JS_DHashTableFinish(&rt->gcRootsHash);
rt->gcRootsHash.ops = NULL;
}
if (rt->gcLocksHash) {
JS_DHashTableDestroy(rt->gcLocksHash);
rt->gcLocksHash = NULL;
}
}
JSBool
js_AddRoot(JSContext *cx, void *rp, const char *name)
{
JSBool ok = js_AddRootRT(cx->runtime, rp, name);
if (!ok)
JS_ReportOutOfMemory(cx);
return ok;
}
JSBool
js_AddRootRT(JSRuntime *rt, void *rp, const char *name)
{
JSBool ok;
JSGCRootHashEntry *rhe;
/*
* Due to the long-standing, but now removed, use of rt->gcLock across the
* bulk of js_GC, API users have come to depend on JS_AddRoot etc. locking
* properly with a racing GC, without calling JS_AddRoot from a request.
* We have to preserve API compatibility here, now that we avoid holding
* rt->gcLock across the mark phase (including the root hashtable mark).
*
* If the GC is running and we're called on another thread, wait for this
* GC activation to finish. We can safely wait here (in the case where we
* are called within a request on another thread's context) without fear
* of deadlock because the GC doesn't set rt->gcRunning until after it has
* waited for all active requests to end.
*/
JS_LOCK_GC(rt);
#ifdef JS_THREADSAFE
JS_ASSERT(!rt->gcRunning || rt->gcLevel > 0);
if (rt->gcRunning && rt->gcThread != js_CurrentThreadId()) {
do {
JS_AWAIT_GC_DONE(rt);
} while (rt->gcLevel > 0);
}
#endif
rhe = (JSGCRootHashEntry *) JS_DHashTableOperate(&rt->gcRootsHash, rp,
JS_DHASH_ADD);
if (rhe) {
rhe->root = rp;
rhe->name = name;
ok = JS_TRUE;
} else {
ok = JS_FALSE;
}
JS_UNLOCK_GC(rt);
return ok;
}
JSBool
js_RemoveRoot(JSRuntime *rt, void *rp)
{
/*
* Due to the JS_RemoveRootRT API, we may be called outside of a request.
* Same synchronization drill as above in js_AddRoot.
*/
JS_LOCK_GC(rt);
#ifdef JS_THREADSAFE
JS_ASSERT(!rt->gcRunning || rt->gcLevel > 0);
if (rt->gcRunning && rt->gcThread != js_CurrentThreadId()) {
do {
JS_AWAIT_GC_DONE(rt);
} while (rt->gcLevel > 0);
}
#endif
(void) JS_DHashTableOperate(&rt->gcRootsHash, rp, JS_DHASH_REMOVE);
rt->gcPoke = JS_TRUE;
JS_UNLOCK_GC(rt);
return JS_TRUE;
}
#ifdef DEBUG_brendan
#define NGCHIST 64
static struct GCHist {
JSBool lastDitch;
JSGCThing *freeList;
} gchist[NGCHIST];
unsigned gchpos;
#endif
void *
js_NewGCThing(JSContext *cx, uintN flags, size_t nbytes)
{
JSBool tried_gc;
JSRuntime *rt;
size_t nflags;
uintN i;
JSGCThing *thing, **flp;
uint8 *flagp;
JSLocalRootStack *lrs;
uint32 *bytesptr;
rt = cx->runtime;
JS_LOCK_GC(rt);
JS_ASSERT(!rt->gcRunning);
if (rt->gcRunning) {
METER(rt->gcStats.finalfail++);
JS_UNLOCK_GC(rt);
return NULL;
}
#ifdef TOO_MUCH_GC
#ifdef WAY_TOO_MUCH_GC
rt->gcPoke = JS_TRUE;
#endif
js_GC(cx, GC_KEEP_ATOMS | GC_ALREADY_LOCKED);
tried_gc = JS_TRUE;
#else
tried_gc = JS_FALSE;
#endif
METER(rt->gcStats.alloc++);
nbytes = JS_ROUNDUP(nbytes, sizeof(JSGCThing));
nflags = nbytes / sizeof(JSGCThing);
i = GC_FREELIST_INDEX(nbytes);
flp = &rt->gcFreeList[i];
retry:
thing = *flp;
if (thing) {
*flp = thing->next;
flagp = thing->flagp;
METER(rt->gcStats.freelen[i]--);
METER(rt->gcStats.recycle[i]++);
} else {
if (rt->gcBytes < rt->gcMaxBytes &&
(tried_gc || rt->gcMallocBytes < rt->gcMaxBytes))
{
/*
* Inline form of JS_ARENA_ALLOCATE adapted to truncate the current
* arena's limit to a GC_PAGE_SIZE boundary, and to skip over every
* GC_PAGE_SIZE-byte-aligned thing (which is actually not a thing,
* it's a JSGCPageInfo record).
*/
JSArenaPool *pool = &rt->gcArenaPool[i];
JSArena *a = pool->current;
jsuword p = a->avail;
jsuword q = p + nbytes;
if (q > (a->limit & ~GC_PAGE_MASK)) {
thing = gc_new_arena(pool, nbytes);
} else {
if ((p & GC_PAGE_MASK) == 0) {
/* Beware, p points to a JSGCPageInfo record! */
p = FIRST_THING(p, nbytes);
q = p + nbytes;
JS_ArenaCountAllocation(pool, p & GC_PAGE_MASK);
}
a->avail = q;
thing = (JSGCThing *)p;
}
JS_ArenaCountAllocation(pool, nbytes);
}
/*
* Consider doing a "last ditch" GC if thing couldn't be allocated.
*
* Keep rt->gcLock across the call into js_GC so we don't starve and
* lose to racing threads who deplete the heap just after js_GC has
* replenished it (or has synchronized with a racing GC that collected
* a bunch of garbage). This unfair scheduling can happen on certain
* operating systems. For the gory details, see Mozilla bug 162779
* (http://bugzilla.mozilla.org/show_bug.cgi?id=162779).
*/
if (!thing) {
if (!tried_gc) {
rt->gcPoke = JS_TRUE;
js_GC(cx, GC_KEEP_ATOMS | GC_ALREADY_LOCKED);
if (JS_HAS_NATIVE_BRANCH_CALLBACK_OPTION(cx) &&
cx->branchCallback &&
!cx->branchCallback(cx, NULL)) {
METER(rt->gcStats.retryhalt++);
JS_UNLOCK_GC(rt);
return NULL;
}
tried_gc = JS_TRUE;
METER(rt->gcStats.retry++);
goto retry;
}
goto fail;
}
/* Find the flags pointer given thing's address. */
flagp = js_GetGCThingFlags(thing);
}
lrs = cx->localRootStack;
if (lrs) {
/*
* If we're in a local root scope, don't set cx->newborn[type] at all,
* to avoid entraining garbage from it for an unbounded amount of time
* on this context. A caller will leave the local root scope and pop
* this reference, allowing thing to be GC'd if it has no other refs.
* See JS_EnterLocalRootScope and related APIs.
*/
if (js_PushLocalRoot(cx, lrs, (jsval) thing) < 0)
goto fail;
} else {
/*
* No local root scope, so we're stuck with the old, fragile model of
* depending on a pigeon-hole newborn per type per context.
*/
cx->newborn[flags & GCF_TYPEMASK] = thing;
}
/* We can't fail now, so update flags and rt->gc{,Private}Bytes. */
*flagp = (uint8)flags;
bytesptr = ((flags & GCF_TYPEMASK) == GCX_PRIVATE)
? &rt->gcPrivateBytes
: &rt->gcBytes;
*bytesptr += nbytes + nflags;
/*
* Clear thing before unlocking in case a GC run is about to scan it,
* finding it via cx->newborn[].
*/
thing->next = NULL;
thing->flagp = NULL;
#ifdef DEBUG_brendan
gchist[gchpos].lastDitch = tried_gc;
gchist[gchpos].freeList = *flp;
if (++gchpos == NGCHIST)
gchpos = 0;
#endif
METER(if (flags & GCF_LOCK) rt->gcStats.lockborn++);
JS_UNLOCK_GC(rt);
return thing;
fail:
METER(rt->gcStats.fail++);
JS_UNLOCK_GC(rt);
JS_ReportOutOfMemory(cx);
return NULL;
}
JSBool
js_LockGCThing(JSContext *cx, void *thing)
{
JSBool ok = js_LockGCThingRT(cx->runtime, thing);
if (!ok)
JS_ReportOutOfMemory(cx);
return ok;
}
/*
* Deep GC-things can't be locked just by setting the GCF_LOCK bit, because
* their descendants must be marked by the GC. To find them during the mark
* phase, they are added to rt->gcLocksHash, which is created lazily.
*
* NB: we depend on the order of GC-thing type indexes here!
*/
#define GC_TYPE_IS_STRING(t) ((t) == GCX_STRING || \
(t) >= GCX_EXTERNAL_STRING)
#define GC_TYPE_IS_XML(t) ((unsigned)((t) - GCX_NAMESPACE) <= \
(unsigned)(GCX_XML - GCX_NAMESPACE))
#define GC_TYPE_IS_DEEP(t) ((t) == GCX_OBJECT || GC_TYPE_IS_XML(t))
#define IS_DEEP_STRING(t,o) (GC_TYPE_IS_STRING(t) && \
JSSTRING_IS_DEPENDENT((JSString *)(o)))
#define GC_THING_IS_DEEP(t,o) (GC_TYPE_IS_DEEP(t) || IS_DEEP_STRING(t, o))
JSBool
js_LockGCThingRT(JSRuntime *rt, void *thing)
{
JSBool ok, deep;
uint8 *flagp, flags, lock, type;
JSGCLockHashEntry *lhe;
ok = JS_TRUE;
if (!thing)
return ok;
flagp = js_GetGCThingFlags(thing);
JS_LOCK_GC(rt);
flags = *flagp;
lock = (flags & GCF_LOCK);
type = (flags & GCF_TYPEMASK);
deep = GC_THING_IS_DEEP(type, thing);
/*
* Avoid adding a rt->gcLocksHash entry for shallow things until someone
* nests a lock -- then start such an entry with a count of 2, not 1.
*/
if (lock || deep) {
if (!rt->gcLocksHash) {
rt->gcLocksHash =
JS_NewDHashTable(JS_DHashGetStubOps(), NULL,
sizeof(JSGCLockHashEntry),
GC_ROOTS_SIZE);
if (!rt->gcLocksHash) {
ok = JS_FALSE;
goto done;
}
} else if (lock == 0) {
#ifdef DEBUG
JSDHashEntryHdr *hdr =
JS_DHashTableOperate(rt->gcLocksHash, thing,
JS_DHASH_LOOKUP);
JS_ASSERT(JS_DHASH_ENTRY_IS_FREE(hdr));
#endif
}
lhe = (JSGCLockHashEntry *)
JS_DHashTableOperate(rt->gcLocksHash, thing, JS_DHASH_ADD);
if (!lhe) {
ok = JS_FALSE;
goto done;
}
if (!lhe->thing) {
lhe->thing = thing;
lhe->count = deep ? 1 : 2;
} else {
JS_ASSERT(lhe->count >= 1);
lhe->count++;
}
}
*flagp = (uint8)(flags | GCF_LOCK);
METER(rt->gcStats.lock++);
ok = JS_TRUE;
done:
JS_UNLOCK_GC(rt);
return ok;
}
JSBool
js_UnlockGCThingRT(JSRuntime *rt, void *thing)
{
uint8 *flagp, flags;
JSGCLockHashEntry *lhe;
if (!thing)
return JS_TRUE;
flagp = js_GetGCThingFlags(thing);
JS_LOCK_GC(rt);
flags = *flagp;
if (flags & GCF_LOCK) {
if (!rt->gcLocksHash ||
(lhe = (JSGCLockHashEntry *)
JS_DHashTableOperate(rt->gcLocksHash, thing,
JS_DHASH_LOOKUP),
JS_DHASH_ENTRY_IS_FREE(&lhe->hdr))) {
/* Shallow GC-thing with an implicit lock count of 1. */
JS_ASSERT(!GC_THING_IS_DEEP(flags & GCF_TYPEMASK, thing));
} else {
/* Basis or nested unlock of a deep thing, or nested of shallow. */
if (--lhe->count != 0)
goto out;
JS_DHashTableOperate(rt->gcLocksHash, thing, JS_DHASH_REMOVE);
}
*flagp = (uint8)(flags & ~GCF_LOCK);
}
rt->gcPoke = JS_TRUE;
out:
METER(rt->gcStats.unlock++);
JS_UNLOCK_GC(rt);
return JS_TRUE;
}
#ifdef GC_MARK_DEBUG
#include <stdio.h>
#include "jsprf.h"
JS_FRIEND_DATA(FILE *) js_DumpGCHeap;
JS_EXPORT_DATA(void *) js_LiveThingToFind;
#ifdef HAVE_XPCONNECT
#include "dump_xpc.h"
#endif
static const char *
gc_object_class_name(void* thing)
{
uint8 *flagp = js_GetGCThingFlags(thing);
const char *className = "";
static char depbuf[32];
switch (*flagp & GCF_TYPEMASK) {
case GCX_OBJECT: {
JSObject *obj = (JSObject *)thing;
JSClass *clasp = JSVAL_TO_PRIVATE(obj->slots[JSSLOT_CLASS]);
className = clasp->name;
#ifdef HAVE_XPCONNECT
if (clasp->flags & JSCLASS_PRIVATE_IS_NSISUPPORTS) {
jsval privateValue = obj->slots[JSSLOT_PRIVATE];
JS_ASSERT(clasp->flags & JSCLASS_HAS_PRIVATE);
if (!JSVAL_IS_VOID(privateValue)) {
void *privateThing = JSVAL_TO_PRIVATE(privateValue);
const char *xpcClassName = GetXPCObjectClassName(privateThing);
if (xpcClassName)
className = xpcClassName;
}
}
#endif
break;
}
case GCX_STRING:
case GCX_MUTABLE_STRING: {
JSString *str = (JSString *)thing;
if (JSSTRING_IS_DEPENDENT(str)) {
JS_snprintf(depbuf, sizeof depbuf, "start:%u, length:%u",
JSSTRDEP_START(str), JSSTRDEP_LENGTH(str));
className = depbuf;
} else {
className = "string";
}
break;
}
case GCX_DOUBLE:
className = "double";
break;
}
return className;
}
static void
gc_dump_thing(JSGCThing *thing, uint8 flags, GCMarkNode *prev, FILE *fp)
{
GCMarkNode *next = NULL;
char *path = NULL;
while (prev) {
next = prev;
prev = prev->prev;
}
while (next) {
uint8 nextFlags = *js_GetGCThingFlags(next->thing);
if ((nextFlags & GCF_TYPEMASK) == GCX_OBJECT) {
path = JS_sprintf_append(path, "%s(%s @ 0x%08p).",
next->name,
gc_object_class_name(next->thing),
(JSObject*)next->thing);
} else {
path = JS_sprintf_append(path, "%s(%s).",
next->name,
gc_object_class_name(next->thing));
}
next = next->next;
}
if (!path)
return;
fprintf(fp, "%08lx ", (long)thing);
switch (flags & GCF_TYPEMASK) {
case GCX_OBJECT:
{
JSObject *obj = (JSObject *)thing;
jsval privateValue = obj->slots[JSSLOT_PRIVATE];
void *privateThing = JSVAL_IS_VOID(privateValue)
? NULL
: JSVAL_TO_PRIVATE(privateValue);
const char *className = gc_object_class_name(thing);
fprintf(fp, "object %8p %s", privateThing, className);
break;
}
#if JS_HAS_XML_SUPPORT
case GCX_NAMESPACE:
{
JSXMLNamespace *ns = (JSXMLNamespace *)thing;
fprintf(fp, "namespace %s:%s",
JS_GetStringBytes(ns->prefix), JS_GetStringBytes(ns->uri));
break;
}
case GCX_QNAME:
{
JSXMLQName *qn = (JSXMLQName *)thing;
fprintf(fp, "qname %s(%s):%s",
JS_GetStringBytes(qn->prefix), JS_GetStringBytes(qn->uri),
JS_GetStringBytes(qn->localName));
break;
}
case GCX_XML:
{
extern const char *js_xml_class_str[];
JSXML *xml = (JSXML *)thing;
fprintf(fp, "xml %8p %s", xml, js_xml_class_str[xml->xml_class]);
break;
}
#endif
case GCX_DOUBLE:
fprintf(fp, "double %g", *(jsdouble *)thing);
break;
case GCX_PRIVATE:
fprintf(fp, "private %8p", (void *)thing);
break;
default:
fprintf(fp, "string %s", JS_GetStringBytes((JSString *)thing));
break;
}
fprintf(fp, " via %s\n", path);
free(path);
}
#endif /* !GC_MARK_DEBUG */
static void
gc_mark_atom_key_thing(void *thing, void *arg)
{
JSContext *cx = (JSContext *) arg;
GC_MARK(cx, thing, "atom", NULL);
}
void
js_MarkAtom(JSContext *cx, JSAtom *atom, void *arg)
{
jsval key;
if (atom->flags & ATOM_MARK)
return;
atom->flags |= ATOM_MARK;
key = ATOM_KEY(atom);
if (JSVAL_IS_GCTHING(key)) {
#ifdef GC_MARK_DEBUG
char name[32];
if (JSVAL_IS_STRING(key)) {
JS_snprintf(name, sizeof name, "'%s'",
JS_GetStringBytes(JSVAL_TO_STRING(key)));
} else {
JS_snprintf(name, sizeof name, "<%x>", key);
}
#endif
GC_MARK(cx, JSVAL_TO_GCTHING(key), name, arg);
}
if (atom->flags & ATOM_HIDDEN)
js_MarkAtom(cx, atom->entry.value, arg);
}
/*
* These macros help avoid passing the GC_MARK_DEBUG-only |arg| parameter
* during recursive calls when GC_MARK_DEBUG is not defined.
*/
#ifdef GC_MARK_DEBUG
# define UNMARKED_GC_THING_FLAGS(thing, arg) \
UnmarkedGCThingFlags(thing, arg)
# define NEXT_UNMARKED_GC_THING(vp, end, thingp, flagpp, arg) \
NextUnmarkedGCThing(vp, end, thingp, flagpp, arg)
# define MARK_GC_THING(cx, thing, flagp, arg) \
MarkGCThing(cx, thing, flagp, arg)
# define CALL_GC_THING_MARKER(marker, cx, thing, arg) \
marker(cx, thing, arg)
#else
# define UNMARKED_GC_THING_FLAGS(thing, arg) \
UnmarkedGCThingFlags(thing)
# define NEXT_UNMARKED_GC_THING(vp, end, thingp, flagpp, arg) \
NextUnmarkedGCThing(vp, end, thingp, flagpp)
# define MARK_GC_THING(cx, thing, flagp, arg) \
MarkGCThing(cx, thing, flagp)
# define CALL_GC_THING_MARKER(marker, cx, thing, arg) \
marker(cx, thing, NULL)
#endif
static uint8 *
UNMARKED_GC_THING_FLAGS(void *thing, void *arg)
{
uint8 flags, *flagp;
if (!thing)
return NULL;
flagp = js_GetGCThingFlags(thing);
flags = *flagp;
JS_ASSERT(flags != GCF_FINAL);
#ifdef GC_MARK_DEBUG
if (js_LiveThingToFind == thing)
gc_dump_thing(thing, flags, arg, stderr);
#endif
if (flags & GCF_MARK)
return NULL;
return flagp;
}
static jsval *
NEXT_UNMARKED_GC_THING(jsval *vp, jsval *end, void **thingp, uint8 **flagpp,
void *arg)
{
jsval v;
void *thing;
uint8 *flagp;
while (vp < end) {
v = *vp;
if (JSVAL_IS_GCTHING(v)) {
thing = JSVAL_TO_GCTHING(v);
flagp = UNMARKED_GC_THING_FLAGS(thing, arg);
if (flagp) {
*thingp = thing;
*flagpp = flagp;
return vp;
}
}
vp++;
}
return NULL;
}
static void
DeutschSchorrWaite(JSContext *cx, void *thing, uint8 *flagp);
static JSBool
MARK_GC_THING(JSContext *cx, void *thing, uint8 *flagp, void *arg)
{
JSRuntime *rt;
JSObject *obj;
jsval v, *vp, *end;
JSString *str;
void *next_thing;
uint8 *next_flagp;
#ifdef JS_GCMETER
uint32 tailCallNesting;
#endif
#ifdef GC_MARK_DEBUG
JSScope *scope;
JSScopeProperty *sprop;
char name[32];
#endif
int stackDummy;
rt = cx->runtime;
METER(tailCallNesting = 0);
METER(if (++rt->gcStats.cdepth > rt->gcStats.maxcdepth)
rt->gcStats.maxcdepth = rt->gcStats.cdepth);
#ifndef GC_MARK_DEBUG
start:
#endif
JS_ASSERT(flagp);
METER(if (++rt->gcStats.depth > rt->gcStats.maxdepth)
rt->gcStats.maxdepth = rt->gcStats.depth);
if (*flagp & GCF_MARK) {
/*
* This should happen only if recursive MARK_GC_THING marks flags
* already stored in the caller's *next_flagp.
*/
goto out;
}
*flagp |= GCF_MARK;
#ifdef GC_MARK_DEBUG
if (js_DumpGCHeap)
gc_dump_thing(thing, *flagp, arg, js_DumpGCHeap);
#endif
switch (*flagp & GCF_TYPEMASK) {
case GCX_OBJECT:
/* If obj->slots is null, obj must be a newborn. */
obj = (JSObject *) thing;
vp = obj->slots;
if (!vp)
goto out;
/* Switch to Deutsch-Schorr-Waite if we exhaust our stack quota. */
if (!JS_CHECK_STACK_SIZE(cx, stackDummy)) {
METER(rt->gcStats.dswmark++);
DeutschSchorrWaite(cx, thing, flagp);
goto out;
}
/* Mark slots if they are small enough to be GC-allocated. */
if ((vp[-1] + 1) * sizeof(jsval) <= GC_NBYTES_MAX)
GC_MARK(cx, vp - 1, "slots", arg);
/* Set up local variables to loop over unmarked things. */
end = vp + ((obj->map->ops->mark)
? CALL_GC_THING_MARKER(obj->map->ops->mark, cx, obj, arg)
: JS_MIN(obj->map->freeslot, obj->map->nslots));
vp = NEXT_UNMARKED_GC_THING(vp, end, &thing, &flagp, arg);
if (!vp)
goto out;
v = *vp;
/*
* Here, thing is the first value in obj->slots referring to an
* unmarked GC-thing.
*/
#ifdef GC_MARK_DEBUG
scope = OBJ_IS_NATIVE(obj) ? OBJ_SCOPE(obj) : NULL;
#endif
for (;;) {
/* Check loop invariants. */
JS_ASSERT(v == *vp && JSVAL_IS_GCTHING(v));
JS_ASSERT(thing == JSVAL_TO_GCTHING(v));
JS_ASSERT(flagp == js_GetGCThingFlags(thing));
#ifdef GC_MARK_DEBUG
if (scope) {
uint32 slot;
jsval nval;
slot = vp - obj->slots;
for (sprop = SCOPE_LAST_PROP(scope); ; sprop = sprop->parent) {
if (!sprop) {
switch (slot) {
case JSSLOT_PROTO:
strcpy(name, js_proto_str);
break;
case JSSLOT_PARENT:
strcpy(name, js_parent_str);
break;
default:
JS_snprintf(name, sizeof name,
"**UNKNOWN SLOT %ld**",
(long)slot);
break;
}
break;
}
if (sprop->slot == slot) {
nval = ID_TO_VALUE(sprop->id);
if (JSVAL_IS_INT(nval)) {
JS_snprintf(name, sizeof name, "%ld",
(long)JSVAL_TO_INT(nval));
} else if (JSVAL_IS_STRING(nval)) {
JS_snprintf(name, sizeof name, "%s",
JS_GetStringBytes(JSVAL_TO_STRING(nval)));
} else {
strcpy(name, "**FINALIZED ATOM KEY**");
}
break;
}
}
} else {
strcpy(name, "**UNKNOWN OBJECT MAP ENTRY**");
}
#endif
do {
vp = NEXT_UNMARKED_GC_THING(vp+1, end, &next_thing, &next_flagp,
arg);
if (!vp) {
/*
* Here thing came from the last unmarked GC-thing slot.
* We can eliminate tail recursion unless GC_MARK_DEBUG
* is defined.
*/
#ifdef GC_MARK_DEBUG
GC_MARK(cx, thing, name, arg);
goto out;
#else
METER(++tailCallNesting);
goto start;
#endif
}
} while (next_thing == thing);
v = *vp;
#ifdef GC_MARK_DEBUG
GC_MARK(cx, thing, name, arg);
#else
MARK_GC_THING(cx, thing, flagp, arg);
#endif
thing = next_thing;
flagp = next_flagp;
}
break;
#ifdef DEBUG
case GCX_STRING:
str = (JSString *)thing;
JS_ASSERT(!JSSTRING_IS_DEPENDENT(str));
break;
#endif
case GCX_MUTABLE_STRING:
str = (JSString *)thing;
if (JSSTRING_IS_DEPENDENT(str)) {
thing = JSSTRDEP_BASE(str);
flagp = UNMARKED_GC_THING_FLAGS(thing, arg);
if (flagp) {
#ifdef GC_MARK_DEBUG
GC_MARK(cx, thing, "base", arg);
goto out;
#else
METER(++tailCallNesting);
goto start;
#endif
}
}
break;
#if JS_HAS_XML_SUPPORT
case GCX_NAMESPACE:
CALL_GC_THING_MARKER(js_MarkXMLNamespace, cx, (JSXMLNamespace *)thing,
arg);
break;
case GCX_QNAME:
CALL_GC_THING_MARKER(js_MarkXMLQName, cx, (JSXMLQName *)thing, arg);
break;
case GCX_XML:
CALL_GC_THING_MARKER(js_MarkXML, cx, (JSXML *)thing, arg);
break;
#endif
}
out:
METER(rt->gcStats.depth -= 1 + tailCallNesting);
METER(rt->gcStats.cdepth--);
return JS_TRUE;
}
/*
* An invalid object reference that's distinct from JSVAL_TRUE and JSVAL_FALSE
* when tagged as a boolean. Used to indicate empty DSW mark stack.
*
* Reversed pointers that link the DSW mark stack through obj->slots entries
* are also tagged as booleans so we can find each pointer and unreverse it.
* Because no object pointer is <= 16, these values can be distinguished from
* JSVAL_EMPTY, JSVAL_TRUE, and JSVAL_FALSE.
*/
#define JSVAL_EMPTY (2 << JSVAL_TAGBITS)
/*
* To optimize native objects to avoid O(n^2) explosion in pathological cases,
* we use a dswIndex member of JSScope to tell where in obj->slots to find the
* reversed pointer. Scrounging space in JSScope by packing existing members
* tighter yielded 16 bits of index, which we use directly if obj->slots has
* 64K or fewer slots. Otherwise we make scope->dswIndex a fixed-point 16-bit
* fraction of the number of slots.
*/
static JS_INLINE uint16
EncodeDSWIndex(jsval *vp, jsval *slots)
{
uint32 nslots, limit, index;
jsdouble d;
nslots = slots[-1];
limit = JS_BIT(16);
index = PTRDIFF(vp, slots, jsval);
JS_ASSERT(index < nslots);
if (nslots > limit) {
d = ((jsdouble)index / nslots) * limit;
JS_ASSERT(0 <= d && d < limit);
return (uint16) d;
}
return (uint16) index;
}
static JS_INLINE uint32
DecodeDSWIndex(uint16 dswIndex, jsval *slots)
{
uint32 nslots, limit;
jsdouble d;
nslots = slots[-1];
limit = JS_BIT(16);
JS_ASSERT(dswIndex < nslots);
if (nslots > limit) {
d = ((jsdouble)dswIndex * nslots) / limit;
JS_ASSERT(0 <= d && d < nslots);
return (uint32) d;
}
return dswIndex;
}
static void
DeutschSchorrWaite(JSContext *cx, void *thing, uint8 *flagp)
{
jsval top, parent, v, *vp, *end;
JSObject *obj;
JSScope *scope;
#ifdef JS_GCMETER
JSRuntime *rt = cx->runtime;
#endif
top = JSVAL_EMPTY;
down:
METER(if (++rt->gcStats.dswdepth > rt->gcStats.maxdswdepth)
rt->gcStats.maxdswdepth = rt->gcStats.dswdepth);
obj = (JSObject *) thing;
parent = OBJECT_TO_JSVAL(obj);
/* Precompute for quick testing to set and get scope->dswIndex. */
scope = (OBJ_IS_NATIVE(obj) && OBJ_SCOPE(obj)->object == obj)
? OBJ_SCOPE(obj)
: NULL;
/* Mark slots if they are small enough to be GC-allocated. */
vp = obj->slots;
if ((vp[-1] + 1) * sizeof(jsval) <= GC_NBYTES_MAX)
GC_MARK(cx, vp - 1, "slots", NULL);
end = vp + ((obj->map->ops->mark)
? obj->map->ops->mark(cx, obj, NULL)
: JS_MIN(obj->map->freeslot, obj->map->nslots));
*flagp |= GCF_MARK;
for (;;) {
while ((vp = NEXT_UNMARKED_GC_THING(vp, end, &thing, &flagp, NULL))
!= NULL) {
v = *vp;
JS_ASSERT(JSVAL_TO_GCTHING(v) == thing);
if (JSVAL_IS_OBJECT(v)) {
*vp = JSVAL_SETTAG(top, JSVAL_BOOLEAN);
top = parent;
if (scope)
scope->dswIndex = EncodeDSWIndex(vp, obj->slots);
goto down;
}
/* Handle string and double GC-things. */
MARK_GC_THING(cx, thing, flagp, NULL);
}
/* If we are back at the root (or we never left it), we're done. */
METER(rt->gcStats.dswdepth--);
if (scope)
scope->dswIndex = 0;
if (top == JSVAL_EMPTY)
return;
/* Time to go back up the spanning tree. */
METER(rt->gcStats.dswup++);
obj = JSVAL_TO_OBJECT(top);
vp = obj->slots;
end = vp + vp[-1];
/*
* If obj is native and owns its own scope, we can minimize the cost
* of searching for the reversed pointer.
*/
scope = (OBJ_IS_NATIVE(obj) && OBJ_SCOPE(obj)->object == obj)
? OBJ_SCOPE(obj)
: NULL;
if (scope)
vp += DecodeDSWIndex(scope->dswIndex, vp);
/*
* Alas, we must search for the reversed pointer. If we used the
* scope->dswIndex hint, we'll step over a few slots for objects with
* a few times 64K slots, etc. For more typical (that is, far fewer
* than 64K slots) native objects that own their own scopes, this loop
* won't iterate at all. The order of complexity for host objects and
* unmutated native objects is O(n^2), but n (4 or 5 in most cases) is
* low enough that we don't care.
*
* We cannot use a reversed pointer into obj->slots, because there
* is no way to find an object from an address within its slots.
*/
v = *vp;
while (v <= JSVAL_TRUE || !JSVAL_IS_BOOLEAN(v)) {
METER(rt->gcStats.dswupstep++);
JS_ASSERT(vp + 1 < end);
v = *++vp;
}
*vp++ = parent;
parent = top;
top = JSVAL_CLRTAG(v);
}
}
void
js_MarkGCThing(JSContext *cx, void *thing, void *arg)
{
uint8 *flagp;
flagp = UNMARKED_GC_THING_FLAGS(thing, arg);
if (!flagp)
return;
MARK_GC_THING(cx, thing, flagp, arg);
}
JS_STATIC_DLL_CALLBACK(JSDHashOperator)
gc_root_marker(JSDHashTable *table, JSDHashEntryHdr *hdr, uint32 num, void *arg)
{
JSGCRootHashEntry *rhe = (JSGCRootHashEntry *)hdr;
jsval *rp = (jsval *)rhe->root;
jsval v = *rp;
/* Ignore null object and scalar values. */
if (!JSVAL_IS_NULL(v) && JSVAL_IS_GCTHING(v)) {
JSContext *cx = (JSContext *)arg;
#ifdef DEBUG
uintN i;
JSArena *a;
jsuword firstpage;
JSBool root_points_to_gcArenaPool = JS_FALSE;
void *thing = JSVAL_TO_GCTHING(v);
for (i = 0; i < GC_NUM_FREELISTS; i++) {
for (a = cx->runtime->gcArenaPool[i].first.next; a; a = a->next) {
firstpage = FIRST_THING_PAGE(a);
if (JS_UPTRDIFF(thing, firstpage) < a->avail - firstpage) {
root_points_to_gcArenaPool = JS_TRUE;
break;
}
}
}
if (!root_points_to_gcArenaPool && rhe->name) {
fprintf(stderr,
"JS API usage error: the address passed to JS_AddNamedRoot currently holds an\n"
"invalid jsval. This is usually caused by a missing call to JS_RemoveRoot.\n"
"The root's name is \"%s\".\n",
rhe->name);
}
JS_ASSERT(root_points_to_gcArenaPool);
#endif
GC_MARK(cx, JSVAL_TO_GCTHING(v), rhe->name ? rhe->name : "root", NULL);
}
return JS_DHASH_NEXT;
}
JS_STATIC_DLL_CALLBACK(JSDHashOperator)
gc_lock_marker(JSDHashTable *table, JSDHashEntryHdr *hdr, uint32 num, void *arg)
{
JSGCLockHashEntry *lhe = (JSGCLockHashEntry *)hdr;
void *thing = (void *)lhe->thing;
JSContext *cx = (JSContext *)arg;
GC_MARK(cx, thing, "locked object", NULL);
return JS_DHASH_NEXT;
}
void
js_ForceGC(JSContext *cx, uintN gcflags)
{
uintN i;
for (i = 0; i < GCX_NTYPES; i++)
cx->newborn[i] = NULL;
cx->lastAtom = NULL;
cx->runtime->gcPoke = JS_TRUE;
js_GC(cx, gcflags);
JS_ArenaFinish();
}
#define GC_MARK_JSVALS(cx, len, vec, name) \
JS_BEGIN_MACRO \
jsval _v, *_vp, *_end; \
\
for (_vp = vec, _end = _vp + len; _vp < _end; _vp++) { \
_v = *_vp; \
if (JSVAL_IS_GCTHING(_v)) \
GC_MARK(cx, JSVAL_TO_GCTHING(_v), name, NULL); \
} \
JS_END_MACRO
void
js_GC(JSContext *cx, uintN gcflags)
{
JSRuntime *rt;
JSContext *iter, *acx;
JSStackFrame *fp, *chain;
uintN i, depth, nslots, type;
JSStackHeader *sh;
JSTempValueRooter *tvr;
size_t nbytes, nflags;
JSArena *a, **ap;
uint8 flags, *flagp, *split;
JSGCThing *thing, *limit, **flp, **oflp;
GCFinalizeOp finalizer;
uint32 *bytesptr;
JSBool all_clear;
#ifdef JS_THREADSAFE
jsword currentThread;
uint32 requestDebit;
#endif
rt = cx->runtime;
#ifdef JS_THREADSAFE
/* Avoid deadlock. */
JS_ASSERT(!JS_IS_RUNTIME_LOCKED(rt));
#endif
/*
* Don't collect garbage if the runtime isn't up, and cx is not the last
* context in the runtime. The last context must force a GC, and nothing
* should suppress that final collection or there may be shutdown leaks,
* or runtime bloat until the next context is created.
*/
if (rt->state != JSRTS_UP && !(gcflags & GC_LAST_CONTEXT))
return;
/*
* Let the API user decide to defer a GC if it wants to (unless this
* is the last context). Invoke the callback regardless.
*/
if (rt->gcCallback) {
if (!rt->gcCallback(cx, JSGC_BEGIN) && !(gcflags & GC_LAST_CONTEXT))
return;
}
/* Lock out other GC allocator and collector invocations. */
if (!(gcflags & GC_ALREADY_LOCKED))
JS_LOCK_GC(rt);
/* Do nothing if no mutator has executed since the last GC. */
if (!rt->gcPoke) {
METER(rt->gcStats.nopoke++);
if (!(gcflags & GC_ALREADY_LOCKED))
JS_UNLOCK_GC(rt);
return;
}
METER(rt->gcStats.poke++);
rt->gcPoke = JS_FALSE;
#ifdef JS_THREADSAFE
/* Bump gcLevel and return rather than nest on this thread. */
currentThread = js_CurrentThreadId();
if (rt->gcThread == currentThread) {
JS_ASSERT(rt->gcLevel > 0);
rt->gcLevel++;
METER(if (rt->gcLevel > rt->gcStats.maxlevel)
rt->gcStats.maxlevel = rt->gcLevel);
if (!(gcflags & GC_ALREADY_LOCKED))
JS_UNLOCK_GC(rt);
return;
}
/*
* If we're in one or more requests (possibly on more than one context)
* running on the current thread, indicate, temporarily, that all these
* requests are inactive. NB: if cx->thread is 0, then cx is not using
* the request model, and does not contribute to rt->requestCount.
*/
requestDebit = 0;
if (cx->thread) {
/*
* Check all contexts for any with the same thread-id. XXX should we
* keep a sub-list of contexts having the same id?
*/
iter = NULL;
while ((acx = js_ContextIterator(rt, JS_FALSE, &iter)) != NULL) {
if (acx->thread == cx->thread && acx->requestDepth)
requestDebit++;
}
} else {
/*
* We assert, but check anyway, in case someone is misusing the API.
* Avoiding the loop over all of rt's contexts is a win in the event
* that the GC runs only on request-less contexts with 0 thread-ids,
* in a special thread such as might be used by the UI/DOM/Layout
* "mozilla" or "main" thread in Mozilla-the-browser.
*/
JS_ASSERT(cx->requestDepth == 0);
if (cx->requestDepth)
requestDebit = 1;
}
if (requestDebit) {
JS_ASSERT(requestDebit <= rt->requestCount);
rt->requestCount -= requestDebit;
if (rt->requestCount == 0)
JS_NOTIFY_REQUEST_DONE(rt);
}
/* If another thread is already in GC, don't attempt GC; wait instead. */
if (rt->gcLevel > 0) {
/* Bump gcLevel to restart the current GC, so it finds new garbage. */
rt->gcLevel++;
METER(if (rt->gcLevel > rt->gcStats.maxlevel)
rt->gcStats.maxlevel = rt->gcLevel);
/* Wait for the other thread to finish, then resume our request. */
while (rt->gcLevel > 0)
JS_AWAIT_GC_DONE(rt);
if (requestDebit)
rt->requestCount += requestDebit;
if (!(gcflags & GC_ALREADY_LOCKED))
JS_UNLOCK_GC(rt);
return;
}
/* No other thread is in GC, so indicate that we're now in GC. */
rt->gcLevel = 1;
rt->gcThread = currentThread;
/* Wait for all other requests to finish. */
while (rt->requestCount > 0)
JS_AWAIT_REQUEST_DONE(rt);
#else /* !JS_THREADSAFE */
/* Bump gcLevel and return rather than nest; the outer gc will restart. */
rt->gcLevel++;
METER(if (rt->gcLevel > rt->gcStats.maxlevel)
rt->gcStats.maxlevel = rt->gcLevel);
if (rt->gcLevel > 1)
return;
#endif /* !JS_THREADSAFE */
/*
* Set rt->gcRunning here within the GC lock, and after waiting for any
* active requests to end, so that new requests that try to JS_AddRoot,
* JS_RemoveRoot, or JS_RemoveRootRT block in JS_BeginRequest waiting for
* rt->gcLevel to drop to zero, while request-less calls to the *Root*
* APIs block in js_AddRoot or js_RemoveRoot (see above in this file),
* waiting for GC to finish.
*/
rt->gcRunning = JS_TRUE;
JS_UNLOCK_GC(rt);
/* If a suspended compile is running on another context, keep atoms. */
if (rt->gcKeepAtoms)
gcflags |= GC_KEEP_ATOMS;
/* Reset malloc counter. */
rt->gcMallocBytes = 0;
/* Drop atoms held by the property cache, and clear property weak links. */
js_DisablePropertyCache(cx);
js_FlushPropertyCache(cx);
#ifdef DEBUG_notme
{ extern void js_DumpScopeMeters(JSRuntime *rt);
js_DumpScopeMeters(rt);
}
#endif
restart:
rt->gcNumber++;
/*
* Mark phase.
*/
JS_DHashTableEnumerate(&rt->gcRootsHash, gc_root_marker, cx);
if (rt->gcLocksHash)
JS_DHashTableEnumerate(rt->gcLocksHash, gc_lock_marker, cx);
js_MarkAtomState(&rt->atomState, gcflags, gc_mark_atom_key_thing, cx);
js_MarkWatchPoints(rt);
js_MarkScriptFilenames(rt, gcflags);
iter = NULL;
while ((acx = js_ContextIterator(rt, JS_TRUE, &iter)) != NULL) {
/*
* Iterate frame chain and dormant chains. Temporarily tack current
* frame onto the head of the dormant list to ease iteration.
*
* (NB: see comment on this whole "dormant" thing in js_Execute.)
*/
chain = acx->fp;
if (chain) {
JS_ASSERT(!chain->dormantNext);
chain->dormantNext = acx->dormantFrameChain;
} else {
chain = acx->dormantFrameChain;
}
for (fp = chain; fp; fp = chain = chain->dormantNext) {
do {
if (fp->callobj)
GC_MARK(cx, fp->callobj, "call object", NULL);
if (fp->argsobj)
GC_MARK(cx, fp->argsobj, "arguments object", NULL);
if (fp->varobj)
GC_MARK(cx, fp->varobj, "variables object", NULL);
if (fp->script) {
js_MarkScript(cx, fp->script, NULL);
if (fp->spbase) {
/*
* Don't mark what has not been pushed yet, or what
* has been popped already.
*/
depth = fp->script->depth;
nslots = (JS_UPTRDIFF(fp->sp, fp->spbase)
< depth * sizeof(jsval))
? (uintN)(fp->sp - fp->spbase)
: depth;
GC_MARK_JSVALS(cx, nslots, fp->spbase, "operand");
}
}
GC_MARK(cx, fp->thisp, "this", NULL);
if (fp->argv) {
nslots = fp->argc;
if (fp->fun) {
if (fp->fun->nargs > nslots)
nslots = fp->fun->nargs;
nslots += fp->fun->extra;
}
GC_MARK_JSVALS(cx, nslots, fp->argv, "arg");
}
if (JSVAL_IS_GCTHING(fp->rval))
GC_MARK(cx, JSVAL_TO_GCTHING(fp->rval), "rval", NULL);
if (fp->vars)
GC_MARK_JSVALS(cx, fp->nvars, fp->vars, "var");
GC_MARK(cx, fp->scopeChain, "scope chain", NULL);
if (fp->sharpArray)
GC_MARK(cx, fp->sharpArray, "sharp array", NULL);
if (fp->xmlNamespace)
GC_MARK(cx, fp->xmlNamespace, "xmlNamespace", NULL);
} while ((fp = fp->down) != NULL);
}
/* Cleanup temporary "dormant" linkage. */
if (acx->fp)
acx->fp->dormantNext = NULL;
/* Mark other roots-by-definition in acx. */
GC_MARK(cx, acx->globalObject, "global object", NULL);
for (i = 0; i < GCX_NTYPES; i++)
GC_MARK(cx, acx->newborn[i], gc_typenames[i], NULL);
if (acx->lastAtom)
GC_MARK_ATOM(cx, acx->lastAtom, NULL);
if (JSVAL_IS_GCTHING(acx->lastInternalResult)) {
thing = JSVAL_TO_GCTHING(acx->lastInternalResult);
if (thing)
GC_MARK(cx, thing, "lastInternalResult", NULL);
}
#if JS_HAS_EXCEPTIONS
if (acx->throwing && JSVAL_IS_GCTHING(acx->exception))
GC_MARK(cx, JSVAL_TO_GCTHING(acx->exception), "exception", NULL);
#endif
#if JS_HAS_LVALUE_RETURN
if (acx->rval2set && JSVAL_IS_GCTHING(acx->rval2))
GC_MARK(cx, JSVAL_TO_GCTHING(acx->rval2), "rval2", NULL);
#endif
for (sh = acx->stackHeaders; sh; sh = sh->down) {
METER(rt->gcStats.stackseg++);
METER(rt->gcStats.segslots += sh->nslots);
GC_MARK_JSVALS(cx, sh->nslots, JS_STACK_SEGMENT(sh), "stack");
}
if (acx->localRootStack)
js_MarkLocalRoots(cx, acx->localRootStack);
for (tvr = acx->tempValueRooters; tvr; tvr = tvr->down) {
if (tvr->count < 0) {
if (JSVAL_IS_GCTHING(tvr->u.value)) {
GC_MARK(cx, JSVAL_TO_GCTHING(tvr->u.value), "tvr->u.value",
NULL);
}
} else {
GC_MARK_JSVALS(cx, tvr->count, tvr->u.array, "tvr->u.array");
}
}
}
#ifdef DUMP_CALL_TABLE
js_DumpCallTable(cx);
#endif
if (rt->gcCallback)
(void) rt->gcCallback(cx, JSGC_MARK_END);
/*
* Sweep phase.
*
* Finalize as we sweep, outside of rt->gcLock, but with rt->gcRunning set
* so that any attempt to allocate a GC-thing from a finalizer will fail,
* rather than nest badly and leave the unmarked newborn to be swept.
*
* Finalize smaller objects before larger, to guarantee finalization of
* GC-allocated obj->slots after obj. See FreeSlots in jsobj.c.
*/
js_SweepAtomState(&rt->atomState);
js_SweepScopeProperties(rt);
js_SweepScriptFilenames(rt);
for (i = 0; i < GC_NUM_FREELISTS; i++) {
nbytes = GC_FREELIST_NBYTES(i);
nflags = nbytes / sizeof(JSGCThing);
for (a = rt->gcArenaPool[i].first.next; a; a = a->next) {
flagp = (uint8 *) a->base;
split = (uint8 *) FIRST_THING_PAGE(a);
limit = (JSGCThing *) a->avail;
for (thing = (JSGCThing *) split; thing < limit; thing += nflags) {
if (((jsuword)thing & GC_PAGE_MASK) == 0) {
thing = (JSGCThing *) FIRST_THING((jsuword)thing, nbytes);
flagp = js_GetGCThingFlags(thing);
}
flags = *flagp;
if (flags & GCF_MARK) {
*flagp &= ~GCF_MARK;
} else if (!(flags & (GCF_LOCK | GCF_FINAL))) {
/* Call the finalizer with GCF_FINAL ORed into flags. */
type = flags & GCF_TYPEMASK;
finalizer = gc_finalizers[type];
if (finalizer) {
*flagp = (uint8)(flags | GCF_FINAL);
if (type >= GCX_EXTERNAL_STRING)
js_PurgeDeflatedStringCache((JSString *)thing);
finalizer(cx, thing);
}
/* Set flags to GCF_FINAL, signifying that thing is free. */
*flagp = GCF_FINAL;
bytesptr = (type == GCX_PRIVATE)
? &rt->gcPrivateBytes
: &rt->gcBytes;
JS_ASSERT(*bytesptr >= nbytes + nflags);
*bytesptr -= nbytes + nflags;
}
flagp += nflags;
if (JS_UPTRDIFF(flagp, split) < nflags)
flagp += GC_THINGS_SIZE;
}
}
}
/*
* Free phase.
* Free any unused arenas and rebuild the JSGCThing freelist.
*/
for (i = 0; i < GC_NUM_FREELISTS; i++) {
ap = &rt->gcArenaPool[i].first.next;
a = *ap;
if (!a)
continue;
all_clear = JS_TRUE;
flp = oflp = &rt->gcFreeList[i];
*flp = NULL;
METER(rt->gcStats.freelen[i] = 0);
nbytes = GC_FREELIST_NBYTES(i);
nflags = nbytes / sizeof(JSGCThing);
do {
flagp = (uint8 *) a->base;
split = (uint8 *) FIRST_THING_PAGE(a);
limit = (JSGCThing *) a->avail;
for (thing = (JSGCThing *) split; thing < limit; thing += nflags) {
if (((jsuword)thing & GC_PAGE_MASK) == 0) {
thing = (JSGCThing *) FIRST_THING((jsuword)thing, nbytes);
flagp = js_GetGCThingFlags(thing);
}
if (*flagp != GCF_FINAL) {
all_clear = JS_FALSE;
} else {
thing->flagp = flagp;
*flp = thing;
flp = &thing->next;
METER(rt->gcStats.freelen[i]++);
}
flagp += nflags;
if (JS_UPTRDIFF(flagp, split) < nflags)
flagp += GC_THINGS_SIZE;
}
if (all_clear) {
JS_ARENA_DESTROY(&rt->gcArenaPool[i], a, ap);
flp = oflp;
METER(rt->gcStats.afree++);
} else {
ap = &a->next;
all_clear = JS_TRUE;
oflp = flp;
}
} while ((a = *ap) != NULL);
/* Terminate the new freelist. */
*flp = NULL;
}
if (rt->gcCallback)
(void) rt->gcCallback(cx, JSGC_FINALIZE_END);
#ifdef DEBUG_notme
{ extern void DumpSrcNoteSizeHist();
DumpSrcNoteSizeHist();
printf("GC HEAP SIZE %lu (%lu)\n",
(unsigned long)rt->gcBytes, (unsigned long)rt->gcPrivateBytes);
}
#endif
JS_LOCK_GC(rt);
if (rt->gcLevel > 1 || rt->gcPoke) {
rt->gcLevel = 1;
rt->gcPoke = JS_FALSE;
JS_UNLOCK_GC(rt);
goto restart;
}
js_EnablePropertyCache(cx);
rt->gcLevel = 0;
rt->gcLastBytes = rt->gcBytes;
rt->gcRunning = JS_FALSE;
#ifdef JS_THREADSAFE
/* If we were invoked during a request, pay back the temporary debit. */
if (requestDebit)
rt->requestCount += requestDebit;
rt->gcThread = 0;
JS_NOTIFY_GC_DONE(rt);
if (!(gcflags & GC_ALREADY_LOCKED))
JS_UNLOCK_GC(rt);
#endif
if (rt->gcCallback) {
if (gcflags & GC_ALREADY_LOCKED)
JS_UNLOCK_GC(rt);
(void) rt->gcCallback(cx, JSGC_END);
if (gcflags & GC_ALREADY_LOCKED)
JS_LOCK_GC(rt);
}
}