mirror of
https://github.com/golang/go
synced 2024-10-04 08:21:22 -06:00
324cc3d040
package main func main() { go func() { *(*int)(nil) = 0 }() select{} } panic: runtime error: invalid memory address or nil pointer dereference [signal 0xb code=0x1 addr=0x0 pc=0x1c96] runtime.panic+0xac /Users/rsc/g/go/src/pkg/runtime/proc.c:1083 runtime.panic(0x11bf0, 0xf8400011f0) runtime.panicstring+0xa3 /Users/rsc/g/go/src/pkg/runtime/runtime.c:116 runtime.panicstring(0x29a57, 0x0) runtime.sigpanic+0x144 /Users/rsc/g/go/src/pkg/runtime/darwin/thread.c:470 runtime.sigpanic() main._func_001+0x16 /Users/rsc/g/go/src/pkg/runtime/x.go:188 main._func_001() runtime.goexit /Users/rsc/g/go/src/pkg/runtime/proc.c:150 runtime.goexit() ----- goroutine created by ----- main.main+0x3d /Users/rsc/g/go/src/pkg/runtime/x.go:4 goroutine 1 [4]: runtime.gosched+0x77 /Users/rsc/g/go/src/pkg/runtime/proc.c:598 runtime.gosched() runtime.block+0x27 /Users/rsc/g/go/src/pkg/runtime/chan.c:680 runtime.block() main.main+0x44 /Users/rsc/g/go/src/pkg/runtime/x.go:5 main.main() runtime.mainstart+0xf /Users/rsc/g/go/src/pkg/runtime/amd64/asm.s:77 runtime.mainstart() runtime.goexit /Users/rsc/g/go/src/pkg/runtime/proc.c:150 runtime.goexit() ----- goroutine created by ----- _rt0_amd64+0x8e /Users/rsc/g/go/src/pkg/runtime/amd64/asm.s:64 Fixes #1563. R=r CC=golang-dev https://golang.org/cl/4243046
855 lines
22 KiB
C
855 lines
22 KiB
C
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Garbage collector.
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#include "runtime.h"
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#include "malloc.h"
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enum {
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Debug = 0,
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UseCas = 1,
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PtrSize = sizeof(void*),
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// Four bits per word (see #defines below).
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wordsPerBitmapWord = sizeof(void*)*8/4,
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bitShift = sizeof(void*)*8/4,
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};
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// Bits in per-word bitmap.
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// #defines because enum might not be able to hold the values.
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//
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// Each word in the bitmap describes wordsPerBitmapWord words
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// of heap memory. There are 4 bitmap bits dedicated to each heap word,
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// so on a 64-bit system there is one bitmap word per 16 heap words.
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// The bits in the word are packed together by type first, then by
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// heap location, so each 64-bit bitmap word consists of, from top to bottom,
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// the 16 bitSpecial bits for the corresponding heap words, then the 16 bitMarked bits,
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// then the 16 bitNoPointers/bitBlockBoundary bits, then the 16 bitAllocated bits.
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// This layout makes it easier to iterate over the bits of a given type.
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//
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// The bitmap starts at mheap.arena_start and extends *backward* from
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// there. On a 64-bit system the off'th word in the arena is tracked by
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// the off/16+1'th word before mheap.arena_start. (On a 32-bit system,
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// the only difference is that the divisor is 8.)
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//
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// To pull out the bits corresponding to a given pointer p, we use:
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//
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// off = p - (uintptr*)mheap.arena_start; // word offset
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// b = (uintptr*)mheap.arena_start - off/wordsPerBitmapWord - 1;
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// shift = off % wordsPerBitmapWord
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// bits = *b >> shift;
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// /* then test bits & bitAllocated, bits & bitMarked, etc. */
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//
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#define bitAllocated ((uintptr)1<<(bitShift*0))
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#define bitNoPointers ((uintptr)1<<(bitShift*1)) /* when bitAllocated is set */
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#define bitMarked ((uintptr)1<<(bitShift*2)) /* when bitAllocated is set */
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#define bitSpecial ((uintptr)1<<(bitShift*3)) /* when bitAllocated is set - has finalizer or being profiled */
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#define bitBlockBoundary ((uintptr)1<<(bitShift*1)) /* when bitAllocated is NOT set */
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#define bitMask (bitBlockBoundary | bitAllocated | bitMarked | bitSpecial)
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static uint64 nlookup;
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static uint64 nsizelookup;
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static uint64 naddrlookup;
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static uint64 nhandoff;
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static int32 gctrace;
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typedef struct Workbuf Workbuf;
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struct Workbuf
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{
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Workbuf *next;
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uintptr nw;
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byte *w[2048-2];
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};
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extern byte data[];
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extern byte etext[];
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extern byte end[];
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static G *fing;
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static Finalizer *finq;
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static int32 fingwait;
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static uint32 nfullwait;
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static void runfinq(void);
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static bool bitlookup(void*, uintptr**, uintptr*, int32*);
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static Workbuf* getempty(Workbuf*);
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static Workbuf* getfull(Workbuf*);
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// scanblock scans a block of n bytes starting at pointer b for references
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// to other objects, scanning any it finds recursively until there are no
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// unscanned objects left. Instead of using an explicit recursion, it keeps
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// a work list in the Workbuf* structures and loops in the main function
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// body. Keeping an explicit work list is easier on the stack allocator and
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// more efficient.
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static void
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scanblock(byte *b, int64 n)
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{
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byte *obj, *arena_start, *p;
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void **vp;
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uintptr size, *bitp, bits, shift, i, j, x, xbits, off;
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MSpan *s;
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PageID k;
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void **bw, **w, **ew;
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Workbuf *wbuf;
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// Memory arena parameters.
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arena_start = runtime·mheap.arena_start;
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wbuf = nil; // current work buffer
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ew = nil; // end of work buffer
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bw = nil; // beginning of work buffer
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w = nil; // current pointer into work buffer
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// Align b to a word boundary.
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off = (uintptr)b & (PtrSize-1);
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if(off != 0) {
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b += PtrSize - off;
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n -= PtrSize - off;
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}
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for(;;) {
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// Each iteration scans the block b of length n, queueing pointers in
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// the work buffer.
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if(Debug > 1)
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runtime·printf("scanblock %p %D\n", b, n);
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vp = (void**)b;
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n /= PtrSize;
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for(i=0; i<n; i++) {
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obj = (byte*)vp[i];
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// Words outside the arena cannot be pointers.
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if((byte*)obj < arena_start || (byte*)obj >= runtime·mheap.arena_used)
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continue;
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// obj may be a pointer to a live object.
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// Try to find the beginning of the object.
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// Round down to word boundary.
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obj = (void*)((uintptr)obj & ~((uintptr)PtrSize-1));
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// Find bits for this word.
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off = (uintptr*)obj - (uintptr*)arena_start;
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bitp = (uintptr*)arena_start - off/wordsPerBitmapWord - 1;
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shift = off % wordsPerBitmapWord;
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xbits = *bitp;
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bits = xbits >> shift;
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// Pointing at the beginning of a block?
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if((bits & (bitAllocated|bitBlockBoundary)) != 0)
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goto found;
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// Pointing just past the beginning?
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// Scan backward a little to find a block boundary.
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for(j=shift; j-->0; ) {
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if(((xbits>>j) & (bitAllocated|bitBlockBoundary)) != 0) {
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obj = (byte*)obj - (shift-j)*PtrSize;
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shift = j;
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bits = xbits>>shift;
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goto found;
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}
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}
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// Otherwise consult span table to find beginning.
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// (Manually inlined copy of MHeap_LookupMaybe.)
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nlookup++;
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naddrlookup++;
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k = (uintptr)obj>>PageShift;
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x = k;
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if(sizeof(void*) == 8)
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x -= (uintptr)arena_start>>PageShift;
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s = runtime·mheap.map[x];
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if(s == nil || k < s->start || k - s->start >= s->npages || s->state != MSpanInUse)
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continue;
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p = (byte*)((uintptr)s->start<<PageShift);
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if(s->sizeclass == 0) {
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obj = p;
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} else {
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if((byte*)obj >= (byte*)s->limit)
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continue;
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size = runtime·class_to_size[s->sizeclass];
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int32 i = ((byte*)obj - p)/size;
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obj = p+i*size;
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}
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// Now that we know the object header, reload bits.
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off = (uintptr*)obj - (uintptr*)arena_start;
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bitp = (uintptr*)arena_start - off/wordsPerBitmapWord - 1;
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shift = off % wordsPerBitmapWord;
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xbits = *bitp;
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bits = xbits >> shift;
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found:
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// Now we have bits, bitp, and shift correct for
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// obj pointing at the base of the object.
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// If not allocated or already marked, done.
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if((bits & bitAllocated) == 0 || (bits & bitMarked) != 0)
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continue;
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*bitp |= bitMarked<<shift;
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// If object has no pointers, don't need to scan further.
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if((bits & bitNoPointers) != 0)
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continue;
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// If buffer is full, get a new one.
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if(w >= ew) {
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wbuf = getempty(wbuf);
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bw = wbuf->w;
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w = bw;
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ew = bw + nelem(wbuf->w);
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}
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*w++ = obj;
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}
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// Done scanning [b, b+n). Prepare for the next iteration of
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// the loop by setting b and n to the parameters for the next block.
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// Fetch b from the work buffers.
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if(w <= bw) {
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// Emptied our buffer: refill.
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wbuf = getfull(wbuf);
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if(wbuf == nil)
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break;
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bw = wbuf->w;
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ew = wbuf->w + nelem(wbuf->w);
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w = bw+wbuf->nw;
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}
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b = *--w;
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// Figure out n = size of b. Start by loading bits for b.
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off = (uintptr*)b - (uintptr*)arena_start;
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bitp = (uintptr*)arena_start - off/wordsPerBitmapWord - 1;
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shift = off % wordsPerBitmapWord;
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xbits = *bitp;
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bits = xbits >> shift;
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// Might be small; look for nearby block boundary.
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// A block boundary is marked by either bitBlockBoundary
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// or bitAllocated being set (see notes near their definition).
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enum {
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boundary = bitBlockBoundary|bitAllocated
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};
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// Look for a block boundary both after and before b
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// in the same bitmap word.
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//
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// A block boundary j words after b is indicated by
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// bits>>j & boundary
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// assuming shift+j < bitShift. (If shift+j >= bitShift then
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// we'll be bleeding other bit types like bitMarked into our test.)
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// Instead of inserting the conditional shift+j < bitShift into the loop,
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// we can let j range from 1 to bitShift as long as we first
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// apply a mask to keep only the bits corresponding
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// to shift+j < bitShift aka j < bitShift-shift.
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bits &= (boundary<<(bitShift-shift)) - boundary;
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// A block boundary j words before b is indicated by
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// xbits>>(shift-j) & boundary
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// (assuming shift >= j). There is no cleverness here
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// avoid the test, because when j gets too large the shift
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// turns negative, which is undefined in C.
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for(j=1; j<bitShift; j++) {
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if(((bits>>j)&boundary) != 0 || shift>=j && ((xbits>>(shift-j))&boundary) != 0) {
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n = j*PtrSize;
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goto scan;
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}
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}
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// Fall back to asking span about size class.
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// (Manually inlined copy of MHeap_Lookup.)
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nlookup++;
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nsizelookup++;
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x = (uintptr)b>>PageShift;
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if(sizeof(void*) == 8)
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x -= (uintptr)arena_start>>PageShift;
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s = runtime·mheap.map[x];
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if(s->sizeclass == 0)
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n = s->npages<<PageShift;
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else
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n = runtime·class_to_size[s->sizeclass];
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scan:;
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}
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}
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static struct {
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Workbuf *full;
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Workbuf *empty;
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byte *chunk;
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uintptr nchunk;
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} work;
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// Get an empty work buffer off the work.empty list,
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// allocating new buffers as needed.
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static Workbuf*
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getempty(Workbuf *b)
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{
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if(b != nil) {
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b->nw = nelem(b->w);
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b->next = work.full;
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work.full = b;
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}
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b = work.empty;
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if(b != nil) {
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work.empty = b->next;
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return b;
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}
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if(work.nchunk < sizeof *b) {
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work.nchunk = 1<<20;
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work.chunk = runtime·SysAlloc(work.nchunk);
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}
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b = (Workbuf*)work.chunk;
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work.chunk += sizeof *b;
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work.nchunk -= sizeof *b;
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return b;
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}
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// Get a full work buffer off the work.full list, or return nil.
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static Workbuf*
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getfull(Workbuf *b)
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{
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if(b != nil) {
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b->nw = 0;
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b->next = work.empty;
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work.empty = b;
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}
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b = work.full;
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if(b != nil)
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work.full = b->next;
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return b;
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}
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// Scanstack calls scanblock on each of gp's stack segments.
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static void
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scanstack(G *gp)
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{
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Stktop *stk;
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byte *sp;
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if(gp == g)
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sp = (byte*)&gp;
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else
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sp = gp->sched.sp;
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if(Debug > 1)
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runtime·printf("scanstack %d %p\n", gp->goid, sp);
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stk = (Stktop*)gp->stackbase;
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while(stk) {
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scanblock(sp, (byte*)stk - sp);
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sp = stk->gobuf.sp;
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stk = (Stktop*)stk->stackbase;
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}
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}
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// Markfin calls scanblock on the blocks that have finalizers:
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// the things pointed at cannot be freed until the finalizers have run.
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static void
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markfin(void *v)
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{
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uintptr size;
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size = 0;
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if(!runtime·mlookup(v, &v, &size, nil) || !runtime·blockspecial(v))
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runtime·throw("mark - finalizer inconsistency");
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// do not mark the finalizer block itself. just mark the things it points at.
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scanblock(v, size);
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}
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// Mark
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static void
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mark(void)
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{
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G *gp;
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// mark data+bss.
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// skip runtime·mheap itself, which has no interesting pointers
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// and is mostly zeroed and would not otherwise be paged in.
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scanblock(data, (byte*)&runtime·mheap - data);
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scanblock((byte*)(&runtime·mheap+1), end - (byte*)(&runtime·mheap+1));
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// mark stacks
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for(gp=runtime·allg; gp!=nil; gp=gp->alllink) {
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switch(gp->status){
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default:
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runtime·printf("unexpected G.status %d\n", gp->status);
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runtime·throw("mark - bad status");
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case Gdead:
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break;
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case Grunning:
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case Grecovery:
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case Gstackalloc:
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if(gp != g)
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runtime·throw("mark - world not stopped");
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scanstack(gp);
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break;
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case Grunnable:
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case Gsyscall:
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case Gwaiting:
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scanstack(gp);
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break;
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}
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}
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// mark things pointed at by objects with finalizers
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runtime·walkfintab(markfin);
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}
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// Sweep frees or calls finalizers for blocks not marked in the mark phase.
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// It clears the mark bits in preparation for the next GC round.
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static void
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sweep(void)
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{
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MSpan *s;
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int32 cl, n, npages;
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uintptr size;
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byte *p;
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MCache *c;
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Finalizer *f;
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for(s = runtime·mheap.allspans; s != nil; s = s->allnext) {
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if(s->state != MSpanInUse)
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continue;
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p = (byte*)(s->start << PageShift);
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cl = s->sizeclass;
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if(cl == 0) {
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size = s->npages<<PageShift;
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n = 1;
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} else {
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// Chunk full of small blocks.
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size = runtime·class_to_size[cl];
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npages = runtime·class_to_allocnpages[cl];
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n = (npages << PageShift) / size;
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}
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// sweep through n objects of given size starting at p.
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for(; n > 0; n--, p += size) {
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uintptr off, *bitp, shift, bits;
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off = (uintptr*)p - (uintptr*)runtime·mheap.arena_start;
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bitp = (uintptr*)runtime·mheap.arena_start - off/wordsPerBitmapWord - 1;
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shift = off % wordsPerBitmapWord;
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bits = *bitp>>shift;
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if((bits & bitAllocated) == 0)
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continue;
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if((bits & bitMarked) != 0) {
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*bitp &= ~(bitMarked<<shift);
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continue;
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}
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if((bits & bitSpecial) != 0) {
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// Special means it has a finalizer or is being profiled.
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f = runtime·getfinalizer(p, 1);
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if(f != nil) {
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f->arg = p;
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f->next = finq;
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finq = f;
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continue;
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}
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runtime·MProf_Free(p, size);
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}
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// Mark freed; restore block boundary bit.
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*bitp = (*bitp & ~(bitMask<<shift)) | (bitBlockBoundary<<shift);
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if(s->sizeclass == 0) {
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// Free large span.
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runtime·unmarkspan(p, 1<<PageShift);
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*(uintptr*)p = 1; // needs zeroing
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runtime·MHeap_Free(&runtime·mheap, s, 1);
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} else {
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// Free small object.
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c = m->mcache;
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if(size > sizeof(uintptr))
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((uintptr*)p)[1] = 1; // mark as "needs to be zeroed"
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mstats.by_size[s->sizeclass].nfree++;
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runtime·MCache_Free(c, p, s->sizeclass, size);
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}
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mstats.alloc -= size;
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mstats.nfree++;
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}
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}
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}
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// Semaphore, not Lock, so that the goroutine
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// reschedules when there is contention rather
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// than spinning.
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static uint32 gcsema = 1;
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// Initialized from $GOGC. GOGC=off means no gc.
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//
|
|
// Next gc is after we've allocated an extra amount of
|
|
// memory proportional to the amount already in use.
|
|
// If gcpercent=100 and we're using 4M, we'll gc again
|
|
// when we get to 8M. This keeps the gc cost in linear
|
|
// proportion to the allocation cost. Adjusting gcpercent
|
|
// just changes the linear constant (and also the amount of
|
|
// extra memory used).
|
|
static int32 gcpercent = -2;
|
|
|
|
static void
|
|
stealcache(void)
|
|
{
|
|
M *m;
|
|
|
|
for(m=runtime·allm; m; m=m->alllink)
|
|
runtime·MCache_ReleaseAll(m->mcache);
|
|
}
|
|
|
|
static void
|
|
cachestats(void)
|
|
{
|
|
M *m;
|
|
MCache *c;
|
|
|
|
for(m=runtime·allm; m; m=m->alllink) {
|
|
c = m->mcache;
|
|
mstats.heap_alloc += c->local_alloc;
|
|
c->local_alloc = 0;
|
|
mstats.heap_objects += c->local_objects;
|
|
c->local_objects = 0;
|
|
}
|
|
}
|
|
|
|
void
|
|
runtime·gc(int32 force)
|
|
{
|
|
int64 t0, t1, t2, t3;
|
|
uint64 heap0, heap1, obj0, obj1;
|
|
byte *p;
|
|
Finalizer *fp;
|
|
|
|
// The gc is turned off (via enablegc) until
|
|
// the bootstrap has completed.
|
|
// Also, malloc gets called in the guts
|
|
// of a number of libraries that might be
|
|
// holding locks. To avoid priority inversion
|
|
// problems, don't bother trying to run gc
|
|
// while holding a lock. The next mallocgc
|
|
// without a lock will do the gc instead.
|
|
if(!mstats.enablegc || m->locks > 0 || runtime·panicking)
|
|
return;
|
|
|
|
if(gcpercent == -2) { // first time through
|
|
p = runtime·getenv("GOGC");
|
|
if(p == nil || p[0] == '\0')
|
|
gcpercent = 100;
|
|
else if(runtime·strcmp(p, (byte*)"off") == 0)
|
|
gcpercent = -1;
|
|
else
|
|
gcpercent = runtime·atoi(p);
|
|
|
|
p = runtime·getenv("GOGCTRACE");
|
|
if(p != nil)
|
|
gctrace = runtime·atoi(p);
|
|
}
|
|
if(gcpercent < 0)
|
|
return;
|
|
|
|
runtime·semacquire(&gcsema);
|
|
if(!force && mstats.heap_alloc < mstats.next_gc) {
|
|
runtime·semrelease(&gcsema);
|
|
return;
|
|
}
|
|
|
|
t0 = runtime·nanotime();
|
|
nlookup = 0;
|
|
nsizelookup = 0;
|
|
naddrlookup = 0;
|
|
|
|
m->gcing = 1;
|
|
runtime·stoptheworld();
|
|
if(runtime·mheap.Lock.key != 0)
|
|
runtime·throw("runtime·mheap locked during gc");
|
|
|
|
cachestats();
|
|
heap0 = mstats.heap_alloc;
|
|
obj0 = mstats.nmalloc - mstats.nfree;
|
|
|
|
mark();
|
|
t1 = runtime·nanotime();
|
|
sweep();
|
|
t2 = runtime·nanotime();
|
|
stealcache();
|
|
|
|
mstats.next_gc = mstats.heap_alloc+mstats.heap_alloc*gcpercent/100;
|
|
m->gcing = 0;
|
|
|
|
m->locks++; // disable gc during the mallocs in newproc
|
|
fp = finq;
|
|
if(fp != nil) {
|
|
// kick off or wake up goroutine to run queued finalizers
|
|
if(fing == nil)
|
|
fing = runtime·newproc1((byte*)runfinq, nil, 0, 0, runtime·gc);
|
|
else if(fingwait) {
|
|
fingwait = 0;
|
|
runtime·ready(fing);
|
|
}
|
|
}
|
|
m->locks--;
|
|
|
|
cachestats();
|
|
heap1 = mstats.heap_alloc;
|
|
obj1 = mstats.nmalloc - mstats.nfree;
|
|
|
|
t3 = runtime·nanotime();
|
|
mstats.pause_ns[mstats.numgc%nelem(mstats.pause_ns)] = t3 - t0;
|
|
mstats.pause_total_ns += t3 - t0;
|
|
mstats.numgc++;
|
|
if(mstats.debuggc)
|
|
runtime·printf("pause %D\n", t3-t0);
|
|
|
|
if(gctrace) {
|
|
runtime·printf("gc%d: %D+%D+%D ms %D -> %D MB %D -> %D (%D-%D) objects %D pointer lookups (%D size, %D addr)\n",
|
|
mstats.numgc, (t1-t0)/1000000, (t2-t1)/1000000, (t3-t2)/1000000,
|
|
heap0>>20, heap1>>20, obj0, obj1,
|
|
mstats.nmalloc, mstats.nfree,
|
|
nlookup, nsizelookup, naddrlookup);
|
|
}
|
|
|
|
runtime·semrelease(&gcsema);
|
|
runtime·starttheworld();
|
|
|
|
// give the queued finalizers, if any, a chance to run
|
|
if(fp != nil)
|
|
runtime·gosched();
|
|
|
|
if(gctrace > 1 && !force)
|
|
runtime·gc(1);
|
|
}
|
|
|
|
static void
|
|
runfinq(void)
|
|
{
|
|
Finalizer *f, *next;
|
|
byte *frame;
|
|
|
|
for(;;) {
|
|
// There's no need for a lock in this section
|
|
// because it only conflicts with the garbage
|
|
// collector, and the garbage collector only
|
|
// runs when everyone else is stopped, and
|
|
// runfinq only stops at the gosched() or
|
|
// during the calls in the for loop.
|
|
f = finq;
|
|
finq = nil;
|
|
if(f == nil) {
|
|
fingwait = 1;
|
|
g->status = Gwaiting;
|
|
runtime·gosched();
|
|
continue;
|
|
}
|
|
for(; f; f=next) {
|
|
next = f->next;
|
|
frame = runtime·mal(sizeof(uintptr) + f->nret);
|
|
*(void**)frame = f->arg;
|
|
reflect·call((byte*)f->fn, frame, sizeof(uintptr) + f->nret);
|
|
runtime·free(frame);
|
|
f->fn = nil;
|
|
f->arg = nil;
|
|
f->next = nil;
|
|
runtime·free(f);
|
|
}
|
|
runtime·gc(1); // trigger another gc to clean up the finalized objects, if possible
|
|
}
|
|
}
|
|
|
|
// mark the block at v of size n as allocated.
|
|
// If noptr is true, mark it as having no pointers.
|
|
void
|
|
runtime·markallocated(void *v, uintptr n, bool noptr)
|
|
{
|
|
uintptr *b, obits, bits, off, shift;
|
|
|
|
if(0)
|
|
runtime·printf("markallocated %p+%p\n", v, n);
|
|
|
|
if((byte*)v+n > (byte*)runtime·mheap.arena_used || (byte*)v < runtime·mheap.arena_start)
|
|
runtime·throw("markallocated: bad pointer");
|
|
|
|
off = (uintptr*)v - (uintptr*)runtime·mheap.arena_start; // word offset
|
|
b = (uintptr*)runtime·mheap.arena_start - off/wordsPerBitmapWord - 1;
|
|
shift = off % wordsPerBitmapWord;
|
|
|
|
for(;;) {
|
|
obits = *b;
|
|
bits = (obits & ~(bitMask<<shift)) | (bitAllocated<<shift);
|
|
if(noptr)
|
|
bits |= bitNoPointers<<shift;
|
|
if(runtime·gomaxprocs == 1) {
|
|
*b = bits;
|
|
break;
|
|
} else {
|
|
// gomaxprocs > 1: use atomic op
|
|
if(runtime·casp((void**)b, (void*)obits, (void*)bits))
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
// mark the block at v of size n as freed.
|
|
void
|
|
runtime·markfreed(void *v, uintptr n)
|
|
{
|
|
uintptr *b, obits, bits, off, shift;
|
|
|
|
if(0)
|
|
runtime·printf("markallocated %p+%p\n", v, n);
|
|
|
|
if((byte*)v+n > (byte*)runtime·mheap.arena_used || (byte*)v < runtime·mheap.arena_start)
|
|
runtime·throw("markallocated: bad pointer");
|
|
|
|
off = (uintptr*)v - (uintptr*)runtime·mheap.arena_start; // word offset
|
|
b = (uintptr*)runtime·mheap.arena_start - off/wordsPerBitmapWord - 1;
|
|
shift = off % wordsPerBitmapWord;
|
|
|
|
for(;;) {
|
|
obits = *b;
|
|
bits = (obits & ~(bitMask<<shift)) | (bitBlockBoundary<<shift);
|
|
if(runtime·gomaxprocs == 1) {
|
|
*b = bits;
|
|
break;
|
|
} else {
|
|
// gomaxprocs > 1: use atomic op
|
|
if(runtime·casp((void**)b, (void*)obits, (void*)bits))
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
// check that the block at v of size n is marked freed.
|
|
void
|
|
runtime·checkfreed(void *v, uintptr n)
|
|
{
|
|
uintptr *b, bits, off, shift;
|
|
|
|
if(!runtime·checking)
|
|
return;
|
|
|
|
if((byte*)v+n > (byte*)runtime·mheap.arena_used || (byte*)v < runtime·mheap.arena_start)
|
|
return; // not allocated, so okay
|
|
|
|
off = (uintptr*)v - (uintptr*)runtime·mheap.arena_start; // word offset
|
|
b = (uintptr*)runtime·mheap.arena_start - off/wordsPerBitmapWord - 1;
|
|
shift = off % wordsPerBitmapWord;
|
|
|
|
bits = *b>>shift;
|
|
if((bits & bitAllocated) != 0) {
|
|
runtime·printf("checkfreed %p+%p: off=%p have=%p\n",
|
|
v, n, off, bits & bitMask);
|
|
runtime·throw("checkfreed: not freed");
|
|
}
|
|
}
|
|
|
|
// mark the span of memory at v as having n blocks of the given size.
|
|
// if leftover is true, there is left over space at the end of the span.
|
|
void
|
|
runtime·markspan(void *v, uintptr size, uintptr n, bool leftover)
|
|
{
|
|
uintptr *b, off, shift;
|
|
byte *p;
|
|
|
|
if((byte*)v+size*n > (byte*)runtime·mheap.arena_used || (byte*)v < runtime·mheap.arena_start)
|
|
runtime·throw("markspan: bad pointer");
|
|
|
|
p = v;
|
|
if(leftover) // mark a boundary just past end of last block too
|
|
n++;
|
|
for(; n-- > 0; p += size) {
|
|
// Okay to use non-atomic ops here, because we control
|
|
// the entire span, and each bitmap word has bits for only
|
|
// one span, so no other goroutines are changing these
|
|
// bitmap words.
|
|
off = (uintptr*)p - (uintptr*)runtime·mheap.arena_start; // word offset
|
|
b = (uintptr*)runtime·mheap.arena_start - off/wordsPerBitmapWord - 1;
|
|
shift = off % wordsPerBitmapWord;
|
|
*b = (*b & ~(bitMask<<shift)) | (bitBlockBoundary<<shift);
|
|
}
|
|
}
|
|
|
|
// unmark the span of memory at v of length n bytes.
|
|
void
|
|
runtime·unmarkspan(void *v, uintptr n)
|
|
{
|
|
uintptr *p, *b, off;
|
|
|
|
if((byte*)v+n > (byte*)runtime·mheap.arena_used || (byte*)v < runtime·mheap.arena_start)
|
|
runtime·throw("markspan: bad pointer");
|
|
|
|
p = v;
|
|
off = p - (uintptr*)runtime·mheap.arena_start; // word offset
|
|
if(off % wordsPerBitmapWord != 0)
|
|
runtime·throw("markspan: unaligned pointer");
|
|
b = (uintptr*)runtime·mheap.arena_start - off/wordsPerBitmapWord - 1;
|
|
n /= PtrSize;
|
|
if(n%wordsPerBitmapWord != 0)
|
|
runtime·throw("unmarkspan: unaligned length");
|
|
// Okay to use non-atomic ops here, because we control
|
|
// the entire span, and each bitmap word has bits for only
|
|
// one span, so no other goroutines are changing these
|
|
// bitmap words.
|
|
n /= wordsPerBitmapWord;
|
|
while(n-- > 0)
|
|
*b-- = 0;
|
|
}
|
|
|
|
bool
|
|
runtime·blockspecial(void *v)
|
|
{
|
|
uintptr *b, off, shift;
|
|
|
|
off = (uintptr*)v - (uintptr*)runtime·mheap.arena_start;
|
|
b = (uintptr*)runtime·mheap.arena_start - off/wordsPerBitmapWord - 1;
|
|
shift = off % wordsPerBitmapWord;
|
|
|
|
return (*b & (bitSpecial<<shift)) != 0;
|
|
}
|
|
|
|
void
|
|
runtime·setblockspecial(void *v)
|
|
{
|
|
uintptr *b, off, shift, bits, obits;
|
|
|
|
off = (uintptr*)v - (uintptr*)runtime·mheap.arena_start;
|
|
b = (uintptr*)runtime·mheap.arena_start - off/wordsPerBitmapWord - 1;
|
|
shift = off % wordsPerBitmapWord;
|
|
|
|
for(;;) {
|
|
obits = *b;
|
|
bits = obits | (bitSpecial<<shift);
|
|
if(runtime·gomaxprocs == 1) {
|
|
*b = bits;
|
|
break;
|
|
} else {
|
|
// gomaxprocs > 1: use atomic op
|
|
if(runtime·casp((void**)b, (void*)obits, (void*)bits))
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
void
|
|
runtime·MHeap_MapBits(MHeap *h)
|
|
{
|
|
// Caller has added extra mappings to the arena.
|
|
// Add extra mappings of bitmap words as needed.
|
|
// We allocate extra bitmap pieces in chunks of bitmapChunk.
|
|
enum {
|
|
bitmapChunk = 8192
|
|
};
|
|
uintptr n;
|
|
|
|
n = (h->arena_used - h->arena_start) / wordsPerBitmapWord;
|
|
n = (n+bitmapChunk-1) & ~(bitmapChunk-1);
|
|
if(h->bitmap_mapped >= n)
|
|
return;
|
|
|
|
runtime·SysMap(h->arena_start - n, n - h->bitmap_mapped);
|
|
h->bitmap_mapped = n;
|
|
}
|