When refreshing after a reboot, force lock allocation

After a reboot, when we refresh Podman's state, we retrieved the
lock from the fresh SHM instance, but we did not mark it as
allocated to prevent it being handed out to other containers and
pods.

Provide a method for marking locks as in-use, and use it when we
refresh Podman state after a reboot.

Fixes #2900

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

1 files changed, 16 insertions, 0 deletions

diff --git a/libpod/lock/in_memory_locks.go b/libpod/lock/in_memory_locks.go
index 7c9605917..f3c842f89 100644
--- a/libpod/lock/in_memory_locks.go
+++ b/libpod/lock/in_memory_locks.go
@@ -90,6 +90,22 @@ func (m *InMemoryManager) RetrieveLock(id uint32) (Locker, error) {
 	return m.locks[id], nil
 }
 
+// AllocateAndRetrieveLock allocates a lock with the given ID (if not already in
+// use) and returns it.
+func (m *InMemoryManager) AllocateAndRetrieveLock(id uint32) (Locker, error) {
+	if id >= m.numLocks {
+		return nil, errors.Errorf("given lock ID %d is too large - this manager only supports lock indexes up to %d", id, m.numLocks)
+	}
+
+	if m.locks[id].allocated {
+		return nil, errors.Errorf("given lock ID %d is already in use, cannot reallocate", id)
+	}
+
+	m.locks[id].allocated = true
+
+	return m.locks[id], nil
+}
+
 // FreeAllLocks frees all locks.
 // This function is DANGEROUS. Please read the full comment in locks.go before
 // trying to use it.