lotus/stores/index_locks.go

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package stores
import (
"context"
"sync"
"golang.org/x/xerrors"
"github.com/filecoin-project/specs-actors/actors/abi"
)
type sectorLock struct {
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lk sync.Mutex
notif *ctxCond
r [FileTypes]uint
w SectorFileType
refs uint // access with indexLocks.lk
}
func (l *sectorLock) canLock(read SectorFileType, write SectorFileType) bool {
for i, b := range write.All() {
if b && l.r[i] > 0 {
return false
}
}
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return l.w&(read|write) == 0
}
func (l *sectorLock) tryLock(read SectorFileType, write SectorFileType) bool {
if !l.canLock(read, write) {
return false
}
for i, set := range read.All() {
if set {
l.r[i]++
}
}
l.w |= write
return true
}
func (l *sectorLock) lock(ctx context.Context, read SectorFileType, write SectorFileType) error {
l.lk.Lock()
defer l.lk.Unlock()
for {
if l.tryLock(read, write) {
return nil
}
if err := l.notif.Wait(ctx); err != nil {
return err
}
}
}
func (l *sectorLock) unlock(read SectorFileType, write SectorFileType) {
l.lk.Lock()
defer l.lk.Unlock()
for i, set := range read.All() {
if set {
l.r[i]--
}
}
l.w &= ^write
l.notif.Broadcast()
}
type indexLocks struct {
lk sync.Mutex
locks map[abi.SectorID]*sectorLock
}
func (i *indexLocks) StorageLock(ctx context.Context, sector abi.SectorID, read SectorFileType, write SectorFileType) error {
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if read|write == 0 {
return nil
}
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if read|write > (1<<FileTypes)-1 {
return xerrors.Errorf("unknown file types specified")
}
i.lk.Lock()
slk, ok := i.locks[sector]
if !ok {
slk = &sectorLock{}
slk.notif = newCtxCond(&slk.lk)
i.locks[sector] = slk
}
slk.refs++
i.lk.Unlock()
if err := slk.lock(ctx, read, write); err != nil {
return err
}
go func() {
// TODO: we can avoid this goroutine with a bit of creativity and reflect
<-ctx.Done()
i.lk.Lock()
slk.unlock(read, write)
slk.refs--
if slk.refs == 0 {
delete(i.locks, sector)
}
i.lk.Unlock()
}()
return nil
}