khenaidoo | 7585a96 | 2021-06-10 16:15:38 -0400 | [diff] [blame] | 1 | /* |
Joey Armstrong | 5f51f2e | 2023-01-17 17:06:26 -0500 | [diff] [blame^] | 2 | * Copyright 2018-2023 Open Networking Foundation (ONF) and the ONF Contributors |
khenaidoo | 7585a96 | 2021-06-10 16:15:38 -0400 | [diff] [blame] | 3 | |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package group |
| 18 | |
| 19 | import ( |
| 20 | "context" |
| 21 | "sync" |
| 22 | |
khenaidoo | d948f77 | 2021-08-11 17:49:24 -0400 | [diff] [blame] | 23 | ofp "github.com/opencord/voltha-protos/v5/go/openflow_13" |
khenaidoo | 7585a96 | 2021-06-10 16:15:38 -0400 | [diff] [blame] | 24 | ) |
| 25 | |
| 26 | // Cache hides all low-level locking & synchronization related to group state updates |
| 27 | type Cache struct { |
| 28 | // this lock protects the groups map, it does not protect individual groups |
| 29 | lock sync.RWMutex |
| 30 | groups map[uint32]*chunk |
| 31 | } |
| 32 | |
| 33 | // chunk keeps a group and the lock for this group |
| 34 | type chunk struct { |
| 35 | // this lock is used to synchronize all access to the group, and also to the "deleted" variable |
| 36 | lock sync.Mutex |
| 37 | deleted bool |
| 38 | |
| 39 | group *ofp.OfpGroupEntry |
| 40 | } |
| 41 | |
| 42 | func NewCache() *Cache { |
| 43 | return &Cache{ |
| 44 | groups: make(map[uint32]*chunk), |
| 45 | } |
| 46 | } |
| 47 | |
| 48 | // LockOrCreate locks this group if it exists, or creates a new group if it does not. |
| 49 | // In the case of group creation, the provided "group" must not be modified afterwards. |
| 50 | func (cache *Cache) LockOrCreate(ctx context.Context, group *ofp.OfpGroupEntry) (*Handle, bool, error) { |
| 51 | // try to use read lock instead of full lock if possible |
| 52 | if handle, have := cache.Lock(group.Desc.GroupId); have { |
| 53 | return handle, false, nil |
| 54 | } |
| 55 | |
| 56 | cache.lock.Lock() |
| 57 | entry, have := cache.groups[group.Desc.GroupId] |
| 58 | if !have { |
| 59 | entry := &chunk{group: group} |
| 60 | cache.groups[group.Desc.GroupId] = entry |
| 61 | entry.lock.Lock() |
| 62 | cache.lock.Unlock() |
| 63 | |
| 64 | return &Handle{loader: cache, chunk: entry}, true, nil |
| 65 | } |
| 66 | cache.lock.Unlock() |
| 67 | |
| 68 | entry.lock.Lock() |
| 69 | if entry.deleted { |
| 70 | entry.lock.Unlock() |
| 71 | return cache.LockOrCreate(ctx, group) |
| 72 | } |
| 73 | return &Handle{loader: cache, chunk: entry}, false, nil |
| 74 | } |
| 75 | |
| 76 | // Lock acquires the lock for this group, and returns a handle which can be used to access the group until it's unlocked. |
| 77 | // This handle ensures that the group cannot be accessed if the lock is not held. |
| 78 | // Returns false if the group is not present. |
| 79 | // TODO: consider accepting a ctx and aborting the lock attempt on cancellation |
| 80 | func (cache *Cache) Lock(id uint32) (*Handle, bool) { |
| 81 | cache.lock.RLock() |
| 82 | entry, have := cache.groups[id] |
| 83 | cache.lock.RUnlock() |
| 84 | |
| 85 | if !have { |
| 86 | return nil, false |
| 87 | } |
| 88 | |
| 89 | entry.lock.Lock() |
| 90 | if entry.deleted { |
| 91 | entry.lock.Unlock() |
| 92 | return cache.Lock(id) |
| 93 | } |
| 94 | return &Handle{loader: cache, chunk: entry}, true |
| 95 | } |
| 96 | |
| 97 | // Handle is allocated for each Lock() call, all modifications are made using it, and it is invalidated by Unlock() |
| 98 | // This enforces correct Lock()-Usage()-Unlock() ordering. |
| 99 | type Handle struct { |
| 100 | loader *Cache |
| 101 | chunk *chunk |
| 102 | } |
| 103 | |
| 104 | // GetReadOnly returns an *ofp.OfpGroupEntry which MUST NOT be modified externally, but which is safe to keep indefinitely |
| 105 | func (h *Handle) GetReadOnly() *ofp.OfpGroupEntry { |
| 106 | return h.chunk.group |
| 107 | } |
| 108 | |
| 109 | // Update updates an existing group in cache. |
| 110 | // The provided "group" must not be modified afterwards. |
| 111 | func (h *Handle) Update(ctx context.Context, group *ofp.OfpGroupEntry) error { |
| 112 | h.chunk.group = group |
| 113 | return nil |
| 114 | } |
| 115 | |
| 116 | // Delete removes the group from the cache |
| 117 | func (h *Handle) Delete(ctx context.Context) error { |
| 118 | h.chunk.deleted = true |
| 119 | |
| 120 | h.loader.lock.Lock() |
| 121 | delete(h.loader.groups, h.chunk.group.Desc.GroupId) |
| 122 | h.loader.lock.Unlock() |
| 123 | |
| 124 | h.Unlock() |
| 125 | return nil |
| 126 | } |
| 127 | |
| 128 | // Unlock releases the lock on the group |
| 129 | func (h *Handle) Unlock() { |
| 130 | if h.chunk != nil { |
| 131 | h.chunk.lock.Unlock() |
| 132 | h.chunk = nil // attempting to access the group through this handle in future will panic |
| 133 | } |
| 134 | } |
| 135 | |
| 136 | // ListIDs returns a snapshot of all the managed group IDs |
| 137 | // TODO: iterating through groups safely is expensive now, since all groups are stored & locked separately |
| 138 | // should avoid this where possible |
| 139 | func (cache *Cache) ListIDs() map[uint32]struct{} { |
| 140 | cache.lock.RLock() |
| 141 | defer cache.lock.RUnlock() |
| 142 | // copy the IDs so caller can safely iterate |
| 143 | ret := make(map[uint32]struct{}, len(cache.groups)) |
| 144 | for id := range cache.groups { |
| 145 | ret[id] = struct{}{} |
| 146 | } |
| 147 | return ret |
| 148 | } |