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index_locks.go
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index_locks.go
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package stores
import (
"context"
"sync"
"golang.org/x/xerrors"
"github.com/filecoin-project/go-state-types/abi"
)
type sectorLock struct {
cond *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
}
}
// check that there are no locks taken for either read or write file types we want
return l.w&read == 0 && l.w&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
}
type lockFn func(l *sectorLock, ctx context.Context, read SectorFileType, write SectorFileType) (bool, error)
func (l *sectorLock) tryLockSafe(ctx context.Context, read SectorFileType, write SectorFileType) (bool, error) {
l.cond.L.Lock()
defer l.cond.L.Unlock()
return l.tryLock(read, write), nil
}
func (l *sectorLock) lock(ctx context.Context, read SectorFileType, write SectorFileType) (bool, error) {
l.cond.L.Lock()
defer l.cond.L.Unlock()
for !l.tryLock(read, write) {
if err := l.cond.Wait(ctx); err != nil {
return false, err
}
}
return true, nil
}
func (l *sectorLock) unlock(read SectorFileType, write SectorFileType) {
l.cond.L.Lock()
defer l.cond.L.Unlock()
for i, set := range read.All() {
if set {
l.r[i]--
}
}
l.w &= ^write
l.cond.Broadcast()
}
type indexLocks struct {
lk sync.Mutex
locks map[abi.SectorID]*sectorLock
}
func (i *indexLocks) lockWith(ctx context.Context, lockFn lockFn, sector abi.SectorID, read SectorFileType, write SectorFileType) (bool, error) {
if read|write == 0 {
return false, nil
}
if read|write > (1<<FileTypes)-1 {
return false, xerrors.Errorf("unknown file types specified")
}
i.lk.Lock()
slk, ok := i.locks[sector]
if !ok {
slk = §orLock{}
slk.cond = newCtxCond(&sync.Mutex{})
i.locks[sector] = slk
}
slk.refs++
i.lk.Unlock()
locked, err := lockFn(slk, ctx, read, write)
if err != nil {
return false, err
}
if !locked {
return false, nil
}
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 true, nil
}
func (i *indexLocks) StorageLock(ctx context.Context, sector abi.SectorID, read SectorFileType, write SectorFileType) error {
ok, err := i.lockWith(ctx, (*sectorLock).lock, sector, read, write)
if err != nil {
return err
}
if !ok {
return xerrors.Errorf("failed to acquire lock")
}
return nil
}
func (i *indexLocks) StorageTryLock(ctx context.Context, sector abi.SectorID, read SectorFileType, write SectorFileType) (bool, error) {
return i.lockWith(ctx, (*sectorLock).tryLockSafe, sector, read, write)
}