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runtime: introduce a type for span states

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Currently span states are untyped constants and the field is just a
uint8. Make this more type-safe by introducing a type for the span
state.

Change-Id: I369bf59fe6e8234475f4921611424fceb7d0a6de
Reviewed-on: https://go-review.googlesource.com/30141
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
This commit is contained in:
Austin Clements 2016-09-09 10:31:27 -04:00
parent 5a6e511c61
commit 6879dbde4e
1 changed files with 19 additions and 17 deletions
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36
src/runtime/mheap.go
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@ -102,9 +102,11 @@ var mheap_ mheap
// * During GC (gcphase != _GCoff), a span *must not* transition from
// stack or in-use to free. Because concurrent GC may read a pointer
// and then look up its span, the span state must be monotonic.
type mSpanState uint8
const (
_MSpanInUse = iota // allocated for garbage collected heap
_MSpanStack // allocated for use by stack allocator
_MSpanInUse mSpanState = iota // allocated for garbage collected heap
_MSpanStack // allocated for use by stack allocator
_MSpanFree
_MSpanDead
)
@ -186,21 +188,21 @@ type mspan struct {
// h->sweepgen is incremented by 2 after every GC
sweepgen uint32
divMul uint32 // for divide by elemsize - divMagic.mul
allocCount uint16 // capacity - number of objects in freelist
sizeclass uint8 // size class
incache bool // being used by an mcache
state uint8 // mspaninuse etc
needzero uint8 // needs to be zeroed before allocation
divShift uint8 // for divide by elemsize - divMagic.shift
divShift2 uint8 // for divide by elemsize - divMagic.shift2
elemsize uintptr // computed from sizeclass or from npages
unusedsince int64 // first time spotted by gc in mspanfree state
npreleased uintptr // number of pages released to the os
limit uintptr // end of data in span
speciallock mutex // guards specials list
specials *special // linked list of special records sorted by offset.
baseMask uintptr // if non-0, elemsize is a power of 2, & this will get object allocation base
divMul uint32 // for divide by elemsize - divMagic.mul
allocCount uint16 // capacity - number of objects in freelist
sizeclass uint8 // size class
incache bool // being used by an mcache
state mSpanState // mspaninuse etc
needzero uint8 // needs to be zeroed before allocation
divShift uint8 // for divide by elemsize - divMagic.shift
divShift2 uint8 // for divide by elemsize - divMagic.shift2
elemsize uintptr // computed from sizeclass or from npages
unusedsince int64 // first time spotted by gc in mspanfree state
npreleased uintptr // number of pages released to the os
limit uintptr // end of data in span
speciallock mutex // guards specials list
specials *special // linked list of special records sorted by offset.
baseMask uintptr // if non-0, elemsize is a power of 2, & this will get object allocation base
}
func (s *mspan) base() uintptr {