diff options
| -rw-r--r-- | pkg/sentry/kernel/futex/futex.go | 25 |
1 files changed, 19 insertions, 6 deletions
diff --git a/pkg/sentry/kernel/futex/futex.go b/pkg/sentry/kernel/futex/futex.go index 3bd5c04af..278cc8143 100644 --- a/pkg/sentry/kernel/futex/futex.go +++ b/pkg/sentry/kernel/futex/futex.go @@ -729,14 +729,14 @@ func (m *Manager) UnlockPI(t Target, addr usermem.Addr, tid uint32, private bool } b := m.lockBucket(&k) - err = m.unlockPILocked(t, addr, tid, b) + err = m.unlockPILocked(t, addr, tid, b, &k) k.release() b.mu.Unlock() return err } -func (m *Manager) unlockPILocked(t Target, addr usermem.Addr, tid uint32, b *bucket) error { +func (m *Manager) unlockPILocked(t Target, addr usermem.Addr, tid uint32, b *bucket, key *Key) error { cur, err := t.LoadUint32(addr) if err != nil { return err @@ -746,7 +746,22 @@ func (m *Manager) unlockPILocked(t Target, addr usermem.Addr, tid uint32, b *buc return syserror.EPERM } - if b.waiters.Empty() { + var next *Waiter // Who's the next owner? + var next2 *Waiter // Who's the one after that? + for w := b.waiters.Front(); w != nil; w = w.Next() { + if !w.key.matches(key) { + continue + } + + if next == nil { + next = w + } else { + next2 = w + break + } + } + + if next == nil { // It's safe to set 0 because there are no waiters, no new owner, and the // executing task is the current owner (no owner died bit). prev, err := t.CompareAndSwapUint32(addr, cur, 0) @@ -761,12 +776,10 @@ func (m *Manager) unlockPILocked(t Target, addr usermem.Addr, tid uint32, b *buc return nil } - next := b.waiters.Front() - // Set next owner's TID, waiters if there are any. Resets owner died bit, if // set, because the executing task takes over as the owner. val := next.tid - if next.Next() != nil { + if next2 != nil { val |= linux.FUTEX_WAITERS } |