Newer
Older
// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package runtime
flagNoScan = _FlagNoScan
flagNoZero = _FlagNoZero
maxTinySize = _TinySize
tinySizeClass = _TinySizeClass
maxSmallSize = _MaxSmallSize
pageShift = _PageShift
pageSize = _PageSize
pageMask = _PageMask
bitsPerPointer = _BitsPerPointer
bitsMask = _BitsMask
pointersPerByte = _PointersPerByte
maxGCMask = _MaxGCMask
bitsDead = _BitsDead
bitsPointer = _BitsPointer
bitsScalar = _BitsScalar
concurrentSweep = _ConcurrentSweep
// Page number (address>>pageShift)
type pageID uintptr
// base address for all 0-byte allocations
var zerobase uintptr
// Allocate an object of size bytes.
// Small objects are allocated from the per-P cache's free lists.
// Large objects (> 32 kB) are allocated straight from the heap.
func mallocgc(size uintptr, typ *_type, flags uint32) unsafe.Pointer {
if flags&flagNoScan == 0 && typ == nil {
gothrow("malloc missing type")
}
// This function must be atomic wrt GC, but for performance reasons
// we don't acquirem/releasem on fast path. The code below does not have
// split stack checks, so it can't be preempted by GC.
// Functions like roundup/add are inlined. And systemstack/racemalloc are nosplit.
// If debugMalloc = true, these assumptions are checked below.
if debugMalloc {
mp := acquirem()
if mp.mallocing != 0 {
gothrow("malloc deadlock")
}
mp.mallocing = 1
if mp.curg != nil {
mp.curg.stackguard0 = ^uintptr(0xfff) | 0xbad
}
}
c := gomcache()
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
var s *mspan
var x unsafe.Pointer
if size <= maxSmallSize {
if flags&flagNoScan != 0 && size < maxTinySize {
// Tiny allocator.
//
// Tiny allocator combines several tiny allocation requests
// into a single memory block. The resulting memory block
// is freed when all subobjects are unreachable. The subobjects
// must be FlagNoScan (don't have pointers), this ensures that
// the amount of potentially wasted memory is bounded.
//
// Size of the memory block used for combining (maxTinySize) is tunable.
// Current setting is 16 bytes, which relates to 2x worst case memory
// wastage (when all but one subobjects are unreachable).
// 8 bytes would result in no wastage at all, but provides less
// opportunities for combining.
// 32 bytes provides more opportunities for combining,
// but can lead to 4x worst case wastage.
// The best case winning is 8x regardless of block size.
//
// Objects obtained from tiny allocator must not be freed explicitly.
// So when an object will be freed explicitly, we ensure that
// its size >= maxTinySize.
//
// SetFinalizer has a special case for objects potentially coming
// from tiny allocator, it such case it allows to set finalizers
// for an inner byte of a memory block.
//
// The main targets of tiny allocator are small strings and
// standalone escaping variables. On a json benchmark
// the allocator reduces number of allocations by ~12% and
// reduces heap size by ~20%.
tinysize := uintptr(c.tinysize)
if size <= tinysize {
tiny := unsafe.Pointer(c.tiny)
// Align tiny pointer for required (conservative) alignment.
if size&7 == 0 {
tiny = roundup(tiny, 8)
} else if size&3 == 0 {
tiny = roundup(tiny, 4)
} else if size&1 == 0 {
tiny = roundup(tiny, 2)
}
size1 := size + (uintptr(tiny) - uintptr(unsafe.Pointer(c.tiny)))
if size1 <= tinysize {
// The object fits into existing tiny block.
x = tiny
c.tiny = (*byte)(add(x, size))
c.tinysize -= uintptr(size1)
c.local_tinyallocs++
if debugMalloc {
mp := acquirem()
if mp.mallocing == 0 {
gothrow("bad malloc")
}
mp.mallocing = 0
if mp.curg != nil {
mp.curg.stackguard0 = mp.curg.stack.lo + _StackGuard
// Note: one releasem for the acquirem just above.
// The other for the acquirem at start of malloc.
releasem(mp)
releasem(mp)
}
return x
}
}
// Allocate a new maxTinySize block.
s = c.alloc[tinySizeClass]
v := s.freelist
Rick Hudson
committed
if v.ptr() == nil {
systemstack(func() {
mCache_Refill(c, tinySizeClass)
})
s = c.alloc[tinySizeClass]
v = s.freelist
}
Rick Hudson
committed
s.freelist = v.ptr().next
s.ref++
//TODO: prefetch v.next
x = unsafe.Pointer(v)
(*[2]uint64)(x)[0] = 0
(*[2]uint64)(x)[1] = 0
// See if we need to replace the existing tiny block with the new one
// based on amount of remaining free space.
if maxTinySize-size > tinysize {
c.tiny = (*byte)(add(x, size))
c.tinysize = uintptr(maxTinySize - size)
}
size = maxTinySize
} else {
var sizeclass int8
if size <= 1024-8 {
sizeclass = size_to_class8[(size+7)>>3]
} else {
sizeclass = size_to_class128[(size-1024+127)>>7]
}
size = uintptr(class_to_size[sizeclass])
s = c.alloc[sizeclass]
v := s.freelist
Rick Hudson
committed
if v.ptr() == nil {
systemstack(func() {
mCache_Refill(c, int32(sizeclass))
})
s = c.alloc[sizeclass]
v = s.freelist
}
Rick Hudson
committed
s.freelist = v.ptr().next
s.ref++
//TODO: prefetch
x = unsafe.Pointer(v)
if flags&flagNoZero == 0 {
Rick Hudson
committed
v.ptr().next = 0
if size > 2*ptrSize && ((*[2]uintptr)(x))[1] != 0 {
memclr(unsafe.Pointer(v), size)
}
}
}
c.local_cachealloc += intptr(size)
var s *mspan
systemstack(func() {
s = largeAlloc(size, uint32(flags))
})
x = unsafe.Pointer(uintptr(s.start << pageShift))
size = uintptr(s.elemsize)
}
if flags&flagNoScan != 0 {
// All objects are pre-marked as noscan.
goto marked
}
// If allocating a defer+arg block, now that we've picked a malloc size
// large enough to hold everything, cut the "asked for" size down to
// just the defer header, so that the GC bitmap will record the arg block
// as containing nothing at all (as if it were unused space at the end of
// a malloc block caused by size rounding).
// The defer arg areas are scanned as part of scanstack.
if typ == deferType {
size0 = unsafe.Sizeof(_defer{})
}
// From here till marked label marking the object as allocated
// and storing type info in the GC bitmap.
{
arena_start := uintptr(unsafe.Pointer(mheap_.arena_start))
off := (uintptr(x) - arena_start) / ptrSize
xbits := (*uint8)(unsafe.Pointer(arena_start - off/wordsPerBitmapByte - 1))
shift := (off % wordsPerBitmapByte) * gcBits
if debugMalloc && ((*xbits>>shift)&(bitMask|bitPtrMask)) != bitBoundary {
println("runtime: bits =", (*xbits>>shift)&(bitMask|bitPtrMask))
gothrow("bad bits in markallocated")
}
var ti, te uintptr
var ptrmask *uint8
// It's one word and it has pointers, it must be a pointer.
*xbits |= (bitsPointer << 2) << shift
goto marked
if typ.kind&kindGCProg != 0 {
nptr := (uintptr(typ.size) + ptrSize - 1) / ptrSize
masksize := nptr
if masksize%2 != 0 {
masksize *= 2 // repeated
masksize = masksize * pointersPerByte / 8 // 4 bits per word
masksize++ // unroll flag in the beginning
if masksize > maxGCMask && typ.gc[1] != 0 {
Russ Cox
committed
// write barriers have not been updated to deal with this case yet.
gothrow("maxGCMask too small for now")
// If the mask is too large, unroll the program directly
// into the GC bitmap. It's 7 times slower than copying
// from the pre-unrolled mask, but saves 1/16 of type size
// memory for the mask.
systemstack(func() {
unrollgcproginplace_m(x, typ, size, size0)
})
ptrmask = (*uint8)(unsafe.Pointer(uintptr(typ.gc[0])))
// Check whether the program is already unrolled
// by checking if the unroll flag byte is set
maskword := uintptr(atomicloadp(unsafe.Pointer(ptrmask)))
if *(*uint8)(unsafe.Pointer(&maskword)) == 0 {
systemstack(func() {
unrollgcprog_m(typ)
})
ptrmask = (*uint8)(add(unsafe.Pointer(ptrmask), 1)) // skip the unroll flag byte
} else {
ptrmask = (*uint8)(unsafe.Pointer(typ.gc[0])) // pointer to unrolled mask
}
if size == 2*ptrSize {
*xbits = *ptrmask | bitBoundary
te = uintptr(typ.size) / ptrSize
// If the type occupies odd number of words, its mask is repeated.
if te%2 == 0 {
te /= 2
}
// Copy pointer bitmask into the bitmap.
for i := uintptr(0); i < size0; i += 2 * ptrSize {
v := *(*uint8)(add(unsafe.Pointer(ptrmask), ti))
ti++
if ti == te {
ti = 0
if i == 0 {
v |= bitBoundary
}
if i+ptrSize == size0 {
v &^= uint8(bitPtrMask << 4)
}
*xbits = v
xbits = (*byte)(add(unsafe.Pointer(xbits), ^uintptr(0)))
if size0%(2*ptrSize) == 0 && size0 < size {
// Mark the word after last object's word as bitsDead.
// GCmarkterminate allocates black
// All slots hold nil so no scanning is needed.
// This may be racing with GC so do it atomically if there can be
// a race marking the bit.
if gcphase == _GCmarktermination {
systemstack(func() {
gcmarknewobject_m(uintptr(x))
})
if raceenabled {
racemalloc(x, size)
}
if debugMalloc {
mp := acquirem()
if mp.mallocing == 0 {
gothrow("bad malloc")
}
mp.mallocing = 0
if mp.curg != nil {
mp.curg.stackguard0 = mp.curg.stack.lo + _StackGuard
// Note: one releasem for the acquirem just above.
// The other for the acquirem at start of malloc.
releasem(mp)
releasem(mp)
}
if debug.allocfreetrace != 0 {
tracealloc(x, size, typ)
}
if rate := MemProfileRate; rate > 0 {
if size < uintptr(rate) && int32(size) < c.next_sample {
c.next_sample -= int32(size)
} else {
Rick Hudson
committed
if memstats.heap_alloc >= memstats.next_gc/2 {
Russ Cox
committed
func loadPtrMask(typ *_type) []uint8 {
var ptrmask *uint8
nptr := (uintptr(typ.size) + ptrSize - 1) / ptrSize
if typ.kind&kindGCProg != 0 {
masksize := nptr
if masksize%2 != 0 {
masksize *= 2 // repeated
}
masksize = masksize * pointersPerByte / 8 // 4 bits per word
masksize++ // unroll flag in the beginning
if masksize > maxGCMask && typ.gc[1] != 0 {
// write barriers have not been updated to deal with this case yet.
gothrow("maxGCMask too small for now")
}
ptrmask = (*uint8)(unsafe.Pointer(uintptr(typ.gc[0])))
// Check whether the program is already unrolled
// by checking if the unroll flag byte is set
maskword := uintptr(atomicloadp(unsafe.Pointer(ptrmask)))
if *(*uint8)(unsafe.Pointer(&maskword)) == 0 {
systemstack(func() {
unrollgcprog_m(typ)
})
Russ Cox
committed
}
ptrmask = (*uint8)(add(unsafe.Pointer(ptrmask), 1)) // skip the unroll flag byte
} else {
ptrmask = (*uint8)(unsafe.Pointer(typ.gc[0])) // pointer to unrolled mask
}
return (*[1 << 30]byte)(unsafe.Pointer(ptrmask))[:(nptr+1)/2]
}
// implementation of new builtin
func newobject(typ *_type) unsafe.Pointer {
if typ.kind&kindNoPointers != 0 {
flags |= flagNoScan
}
return mallocgc(uintptr(typ.size), typ, flags)
//go:linkname reflect_unsafe_New reflect.unsafe_New
func reflect_unsafe_New(typ *_type) unsafe.Pointer {
return newobject(typ)
}
// implementation of make builtin for slices
func newarray(typ *_type, n uintptr) unsafe.Pointer {
if typ.kind&kindNoPointers != 0 {
flags |= flagNoScan
}
if int(n) < 0 || (typ.size > 0 && n > _MaxMem/uintptr(typ.size)) {
panic("runtime: allocation size out of range")
}
return mallocgc(uintptr(typ.size)*n, typ, flags)
//go:linkname reflect_unsafe_NewArray reflect.unsafe_NewArray
func reflect_unsafe_NewArray(typ *_type, n uintptr) unsafe.Pointer {
return newarray(typ, n)
}
// rawmem returns a chunk of pointerless memory. It is
// not zeroed.
func rawmem(size uintptr) unsafe.Pointer {
return mallocgc(size, nil, flagNoScan|flagNoZero)
// round size up to next size class
func goroundupsize(size uintptr) uintptr {
if size < maxSmallSize {
if size <= 1024-8 {
return uintptr(class_to_size[size_to_class8[(size+7)>>3]])
}
return uintptr(class_to_size[size_to_class128[(size-1024+127)>>7]])
}
if size+pageSize < size {
return size
}
return (size + pageSize - 1) &^ pageMask
}
func profilealloc(mp *m, x unsafe.Pointer, size uintptr) {
c := mp.mcache
rate := MemProfileRate
if size < uintptr(rate) {
// pick next profile time
// If you change this, also change allocmcache.
if rate > 0x3fffffff { // make 2*rate not overflow
rate = 0x3fffffff
}
next := int32(fastrand1()) % (2 * int32(rate))
// Subtract the "remainder" of the current allocation.
// Otherwise objects that are close in size to sampling rate
// will be under-sampled, because we consistently discard this remainder.
next -= (int32(size) - c.next_sample)
if next < 0 {
next = 0
}
c.next_sample = next
}
// For now this must be bracketed with a stoptheworld and a starttheworld to ensure
// all go routines see the new barrier.
func gcinstallmarkwb() {
gcphase = _GCmark
}
// force = 0 - start concurrent GC
// force = 1 - do STW GC regardless of current heap usage
// force = 2 - go STW GC and eager sweep
// 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 deadlocks during stoptheworld, don't bother
// trying to run gc while holding a lock. The next mallocgc without a lock
// will do the gc instead.
if gp := getg(); gp == mp.g0 || mp.locks > 1 || !memstats.enablegc || panicking != 0 || gcpercent < 0 {
releasem(mp)
return
}
releasem(mp)
semacquire(&worldsema, false)
if force == 0 && memstats.heap_alloc < memstats.next_gc {
// typically threads which lost the race to grab
// worldsema exit here when gc is done.
semrelease(&worldsema)
return
}
// Pick up the remaining unswept/not being swept spans concurrently
for gosweepone() != ^uintptr(0) {
sweep.nbgsweep++
}
// Ok, we're doing it! Stop everybody else
startTime := nanotime()
gctimer.count++
if force == 0 {
gctimer.cycle.sweepterm = nanotime()
}
systemstack(stoptheworld)
systemstack(finishsweep_m) // finish sweep before we start concurrent scan.
if force == 0 { // Do as much work concurrently as possible
gctimer.cycle.scan = nanotime()
// Do a concurrent heap scan before we stop the world.
gctimer.cycle.installmarkwb = nanotime()
gcinstallmarkwb()
gctimer.cycle.mark = nanotime()
gctimer.cycle.markterm = nanotime()
systemstack(stoptheworld)
systemstack(gcinstalloffwb_m)
if mp != acquirem() {
gothrow("gogc: rescheduled")
}
clearpools()
// Run gc on the g0 stack. We do this so that the g stack
// we're currently running on will no longer change. Cuts
// the root set down a bit (g0 stacks are not scanned, and
// we don't need to scan gc's internal state). We also
// need to switch to g0 so we can shrink the stack.
n := 1
if debug.gctrace > 1 {
n = 2
}
startTime = nanotime()
}
// switch to g0, call gc, then switch back
systemstack(func() {
gc_m(startTime, eagersweep)
})
systemstack(func() {
gccheckmark_m(startTime, eagersweep)
})
if force == 0 {
gctimer.cycle.sweep = nanotime()
}
if force == 0 {
if gctimer.verbose > 1 {
GCprinttimes()
} else if gctimer.verbose > 0 {
calctimes() // ignore result
}
}
systemstack(starttheworld)
// now that gc is done, kick off finalizer thread if needed
if !concurrentSweep {
// give the queued finalizers, if any, a chance to run
func GCcheckmarkenable() {
systemstack(gccheckmarkenable_m)
}
func GCcheckmarkdisable() {
systemstack(gccheckmarkdisable_m)
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
// gctimes records the time in nanoseconds of each phase of the concurrent GC.
type gctimes struct {
sweepterm int64 // stw
scan int64 // stw
installmarkwb int64
mark int64
markterm int64 // stw
sweep int64
}
// gcchronograph holds timer information related to GC phases
// max records the maximum time spent in each GC phase since GCstarttimes.
// total records the total time spent in each GC phase since GCstarttimes.
// cycle records the absolute time (as returned by nanoseconds()) that each GC phase last started at.
type gcchronograph struct {
count int64
verbose int64
maxpause int64
max gctimes
total gctimes
cycle gctimes
}
var gctimer gcchronograph
// GCstarttimes initializes the gc timess. All previous timess are lost.
func GCstarttimes(verbose int64) {
gctimer = gcchronograph{verbose: verbose}
}
// GCendtimes stops the gc timers.
func GCendtimes() {
gctimer.verbose = 0
}
// calctimes converts gctimer.cycle into the elapsed times, updates gctimer.total
// and updates gctimer.max with the max pause time.
func calctimes() gctimes {
var times gctimes
var max = func(a, b int64) int64 {
if a > b {
return a
}
return b
}
times.sweepterm = gctimer.cycle.scan - gctimer.cycle.sweepterm
gctimer.total.sweepterm += times.sweepterm
gctimer.max.sweepterm = max(gctimer.max.sweepterm, times.sweepterm)
gctimer.maxpause = max(gctimer.maxpause, gctimer.max.sweepterm)
times.scan = gctimer.cycle.installmarkwb - gctimer.cycle.scan
gctimer.total.scan += times.scan
gctimer.max.scan = max(gctimer.max.scan, times.scan)
times.installmarkwb = gctimer.cycle.mark - gctimer.cycle.installmarkwb
gctimer.total.installmarkwb += times.installmarkwb
gctimer.max.installmarkwb = max(gctimer.max.installmarkwb, times.installmarkwb)
gctimer.maxpause = max(gctimer.maxpause, gctimer.max.installmarkwb)
times.mark = gctimer.cycle.markterm - gctimer.cycle.mark
gctimer.total.mark += times.mark
gctimer.max.mark = max(gctimer.max.mark, times.mark)
times.markterm = gctimer.cycle.sweep - gctimer.cycle.markterm
gctimer.total.markterm += times.markterm
gctimer.max.markterm = max(gctimer.max.markterm, times.markterm)
gctimer.maxpause = max(gctimer.maxpause, gctimer.max.markterm)
return times
}
// GCprinttimes prints latency information in nanoseconds about various
// phases in the GC. The information for each phase includes the maximum pause
// and total time since the most recent call to GCstarttimes as well as
// the information from the most recent Concurent GC cycle. Calls from the
// application to runtime.GC() are ignored.
func GCprinttimes() {
times := calctimes()
println("GC:", gctimer.count, "maxpause=", gctimer.maxpause, "Go routines=", allglen)
println(" sweep termination: max=", gctimer.max.sweepterm, "total=", gctimer.total.sweepterm, "cycle=", times.sweepterm, "absolute time=", gctimer.cycle.sweepterm)
println(" scan: max=", gctimer.max.scan, "total=", gctimer.total.scan, "cycle=", times.scan, "absolute time=", gctimer.cycle.scan)
println(" installmarkwb: max=", gctimer.max.installmarkwb, "total=", gctimer.total.installmarkwb, "cycle=", times.installmarkwb, "absolute time=", gctimer.cycle.installmarkwb)
println(" mark: max=", gctimer.max.mark, "total=", gctimer.total.mark, "cycle=", times.mark, "absolute time=", gctimer.cycle.mark)
println(" markterm: max=", gctimer.max.markterm, "total=", gctimer.total.markterm, "cycle=", times.markterm, "absolute time=", gctimer.cycle.markterm)
cycletime := gctimer.cycle.sweep - gctimer.cycle.sweepterm
println(" Total cycle time =", cycletime)
totalstw := times.sweepterm + times.installmarkwb + times.markterm
println(" Cycle STW time =", totalstw)
}
// GC runs a garbage collection.
func GC() {
gogc(2)
}
// linker-provided
var noptrdata struct{}
Russ Cox
committed
var enoptrdata struct{}
var noptrbss struct{}
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
// SetFinalizer sets the finalizer associated with x to f.
// When the garbage collector finds an unreachable block
// with an associated finalizer, it clears the association and runs
// f(x) in a separate goroutine. This makes x reachable again, but
// now without an associated finalizer. Assuming that SetFinalizer
// is not called again, the next time the garbage collector sees
// that x is unreachable, it will free x.
//
// SetFinalizer(x, nil) clears any finalizer associated with x.
//
// The argument x must be a pointer to an object allocated by
// calling new or by taking the address of a composite literal.
// The argument f must be a function that takes a single argument
// to which x's type can be assigned, and can have arbitrary ignored return
// values. If either of these is not true, SetFinalizer aborts the
// program.
//
// Finalizers are run in dependency order: if A points at B, both have
// finalizers, and they are otherwise unreachable, only the finalizer
// for A runs; once A is freed, the finalizer for B can run.
// If a cyclic structure includes a block with a finalizer, that
// cycle is not guaranteed to be garbage collected and the finalizer
// is not guaranteed to run, because there is no ordering that
// respects the dependencies.
//
// The finalizer for x is scheduled to run at some arbitrary time after
// x becomes unreachable.
// There is no guarantee that finalizers will run before a program exits,
// so typically they are useful only for releasing non-memory resources
// associated with an object during a long-running program.
// For example, an os.File object could use a finalizer to close the
// associated operating system file descriptor when a program discards
// an os.File without calling Close, but it would be a mistake
// to depend on a finalizer to flush an in-memory I/O buffer such as a
// bufio.Writer, because the buffer would not be flushed at program exit.
//
// It is not guaranteed that a finalizer will run if the size of *x is
// zero bytes.
//
// It is not guaranteed that a finalizer will run for objects allocated
// in initializers for package-level variables. Such objects may be
// linker-allocated, not heap-allocated.
//
// A single goroutine runs all finalizers for a program, sequentially.
// If a finalizer must run for a long time, it should do so by starting
// a new goroutine.
func SetFinalizer(obj interface{}, finalizer interface{}) {
e := (*eface)(unsafe.Pointer(&obj))
etyp := e._type
if etyp == nil {
gothrow("runtime.SetFinalizer: first argument is nil")
}
if etyp.kind&kindMask != kindPtr {
gothrow("runtime.SetFinalizer: first argument is " + *etyp._string + ", not pointer")
}
ot := (*ptrtype)(unsafe.Pointer(etyp))
if ot.elem == nil {
gothrow("nil elem type!")
}
// find the containing object
_, base, _ := findObject(e.data)
if base == nil {
// 0-length objects are okay.
if e.data == unsafe.Pointer(&zerobase) {
return
}
// Global initializers might be linker-allocated.
// var Foo = &Object{}
// func main() {
// runtime.SetFinalizer(Foo, nil)
// }
Russ Cox
committed
// The relevant segments are: noptrdata, data, bss, noptrbss.
// We cannot assume they are in any order or even contiguous,
// due to external linking.
if uintptr(unsafe.Pointer(&noptrdata)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&enoptrdata)) ||
uintptr(unsafe.Pointer(&data)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&edata)) ||
uintptr(unsafe.Pointer(&bss)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&ebss)) ||
uintptr(unsafe.Pointer(&noptrbss)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&enoptrbss)) {
return
}
gothrow("runtime.SetFinalizer: pointer not in allocated block")
}
if e.data != base {
// As an implementation detail we allow to set finalizers for an inner byte
// of an object if it could come from tiny alloc (see mallocgc for details).
if ot.elem == nil || ot.elem.kind&kindNoPointers == 0 || ot.elem.size >= maxTinySize {
gothrow("runtime.SetFinalizer: pointer not at beginning of allocated block")
}
}
f := (*eface)(unsafe.Pointer(&finalizer))
ftyp := f._type
// switch to system stack and remove finalizer
systemstack(func() {
removefinalizer(e.data)
})
return
}
if ftyp.kind&kindMask != kindFunc {
gothrow("runtime.SetFinalizer: second argument is " + *ftyp._string + ", not a function")
}
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
ft := (*functype)(unsafe.Pointer(ftyp))
ins := *(*[]*_type)(unsafe.Pointer(&ft.in))
if ft.dotdotdot || len(ins) != 1 {
gothrow("runtime.SetFinalizer: cannot pass " + *etyp._string + " to finalizer " + *ftyp._string)
}
fint := ins[0]
switch {
case fint == etyp:
// ok - same type
goto okarg
case fint.kind&kindMask == kindPtr:
if (fint.x == nil || fint.x.name == nil || etyp.x == nil || etyp.x.name == nil) && (*ptrtype)(unsafe.Pointer(fint)).elem == ot.elem {
// ok - not same type, but both pointers,
// one or the other is unnamed, and same element type, so assignable.
goto okarg
}
case fint.kind&kindMask == kindInterface:
ityp := (*interfacetype)(unsafe.Pointer(fint))
if len(ityp.mhdr) == 0 {
// ok - satisfies empty interface
goto okarg
}
if _, ok := assertE2I2(ityp, obj); ok {
goto okarg
}
}
gothrow("runtime.SetFinalizer: cannot pass " + *etyp._string + " to finalizer " + *ftyp._string)
okarg:
// compute size needed for return parameters
nret := uintptr(0)
for _, t := range *(*[]*_type)(unsafe.Pointer(&ft.out)) {
nret = round(nret, uintptr(t.align)) + uintptr(t.size)
}
nret = round(nret, ptrSize)
// make sure we have a finalizer goroutine
createfing()
systemstack(func() {
if !addfinalizer(e.data, (*funcval)(f.data), nret, fint, ot) {
gothrow("runtime.SetFinalizer: finalizer already set")
}
})
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
// round n up to a multiple of a. a must be a power of 2.
func round(n, a uintptr) uintptr {
return (n + a - 1) &^ (a - 1)
}
// Look up pointer v in heap. Return the span containing the object,
// the start of the object, and the size of the object. If the object
// does not exist, return nil, nil, 0.
func findObject(v unsafe.Pointer) (s *mspan, x unsafe.Pointer, n uintptr) {
c := gomcache()
c.local_nlookup++
if ptrSize == 4 && c.local_nlookup >= 1<<30 {
// purge cache stats to prevent overflow
lock(&mheap_.lock)
purgecachedstats(c)
unlock(&mheap_.lock)
}
// find span
arena_start := uintptr(unsafe.Pointer(mheap_.arena_start))
arena_used := uintptr(unsafe.Pointer(mheap_.arena_used))
if uintptr(v) < arena_start || uintptr(v) >= arena_used {
return
}
p := uintptr(v) >> pageShift
q := p - arena_start>>pageShift
s = *(**mspan)(add(unsafe.Pointer(mheap_.spans), q*ptrSize))
if s == nil {
return
}
x = unsafe.Pointer(uintptr(s.start) << pageShift)
if uintptr(v) < uintptr(x) || uintptr(v) >= uintptr(unsafe.Pointer(s.limit)) || s.state != mSpanInUse {
s = nil
x = nil
return
}
n = uintptr(s.elemsize)
if s.sizeclass != 0 {
x = add(x, (uintptr(v)-uintptr(x))/n*n)
}
return
}
var fingCreate uint32
func createfing() {
// start the finalizer goroutine exactly once
if fingCreate == 0 && cas(&fingCreate, 0, 1) {
go runfinq()
}
}
// This is the goroutine that runs all of the finalizers
func runfinq() {
var (
frame unsafe.Pointer
framecap uintptr
)
for {
lock(&finlock)
fb := finq
finq = nil
if fb == nil {
gp := getg()
fing = gp
fingwait = true
gp.issystem = true
goparkunlock(&finlock, "finalizer wait")
gp.issystem = false
continue
}
unlock(&finlock)
if raceenabled {
racefingo()
}
for fb != nil {
for i := int32(0); i < fb.cnt; i++ {
f := (*finalizer)(add(unsafe.Pointer(&fb.fin), uintptr(i)*unsafe.Sizeof(finalizer{})))
framesz := unsafe.Sizeof((interface{})(nil)) + uintptr(f.nret)
if framecap < framesz {
// The frame does not contain pointers interesting for GC,
// all not yet finalized objects are stored in finq.
// If we do not mark it as FlagNoScan,
// the last finalized object is not collected.
frame = mallocgc(framesz, nil, flagNoScan)
framecap = framesz
}
if f.fint == nil {
gothrow("missing type in runfinq")
}
switch f.fint.kind & kindMask {
case kindPtr:
// direct use of pointer
*(*unsafe.Pointer)(frame) = f.arg
case kindInterface:
ityp := (*interfacetype)(unsafe.Pointer(f.fint))
// set up with empty interface
(*eface)(frame)._type = &f.ot.typ
(*eface)(frame).data = f.arg
if len(ityp.mhdr) != 0 {
// convert to interface with methods
// this conversion is guaranteed to succeed - we checked in SetFinalizer
*(*fInterface)(frame) = assertE2I(ityp, *(*interface{})(frame))
}
default:
gothrow("bad kind in runfinq")
}
reflectcall(unsafe.Pointer(f.fn), frame, uint32(framesz), uint32(framesz))
// drop finalizer queue references to finalized object
f.fn = nil
f.arg = nil
f.ot = nil
}
fb.cnt = 0
next := fb.next
lock(&finlock)
fb.next = finc
finc = fb
unlock(&finlock)
fb = next
}
}
}
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
var persistent struct {
lock mutex
pos unsafe.Pointer
end unsafe.Pointer
}
// Wrapper around sysAlloc that can allocate small chunks.
// There is no associated free operation.
// Intended for things like function/type/debug-related persistent data.
// If align is 0, uses default align (currently 8).
func persistentalloc(size, align uintptr, stat *uint64) unsafe.Pointer {
const (
chunk = 256 << 10
maxBlock = 64 << 10 // VM reservation granularity is 64K on windows
)
if align != 0 {
if align&(align-1) != 0 {
gothrow("persistentalloc: align is not a power of 2")
}
if align > _PageSize {
gothrow("persistentalloc: align is too large")
}
} else {
align = 8
}
if size >= maxBlock {