1 /*
2  * Copyright (C) 2020 The Android Open Source Project
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 #pragma once
18 
19 #include <atomic>
20 #include <list>
21 #include <mutex>
22 
23 #include "LogBuffer.h"
24 #include "LogBufferElement.h"
25 #include "LogReaderList.h"
26 #include "LogStatistics.h"
27 #include "LogTags.h"
28 #include "rwlock.h"
29 
30 class SimpleLogBuffer : public LogBuffer {
31   public:
32     SimpleLogBuffer(LogReaderList* reader_list, LogTags* tags, LogStatistics* stats);
33     ~SimpleLogBuffer();
34     void Init() override final;
35 
36     int Log(log_id_t log_id, log_time realtime, uid_t uid, pid_t pid, pid_t tid, const char* msg,
37             uint16_t len) override;
38     std::unique_ptr<FlushToState> CreateFlushToState(uint64_t start, LogMask log_mask) override;
39     bool FlushTo(LogWriter* writer, FlushToState& state,
40                  const std::function<FilterResult(log_id_t log_id, pid_t pid, uint64_t sequence,
41                                                   log_time realtime)>& filter) override;
42 
43     bool Clear(log_id_t id, uid_t uid) override;
44     unsigned long GetSize(log_id_t id) override;
45     int SetSize(log_id_t id, unsigned long size) override final;
46 
sequence()47     uint64_t sequence() const override { return sequence_.load(std::memory_order_relaxed); }
48 
49   protected:
50     virtual bool Prune(log_id_t id, unsigned long prune_rows, uid_t uid) REQUIRES(lock_);
51     virtual void LogInternal(LogBufferElement&& elem) REQUIRES(lock_);
52 
53     // Returns an iterator to the oldest element for a given log type, or logs_.end() if
54     // there are no logs for the given log type. Requires logs_lock_ to be held.
55     std::list<LogBufferElement>::iterator GetOldest(log_id_t log_id) REQUIRES(lock_);
56     std::list<LogBufferElement>::iterator Erase(std::list<LogBufferElement>::iterator it)
57             REQUIRES(lock_);
58     void KickReader(LogReaderThread* reader, log_id_t id, unsigned long prune_rows)
59             REQUIRES_SHARED(lock_);
60 
stats()61     LogStatistics* stats() { return stats_; }
reader_list()62     LogReaderList* reader_list() { return reader_list_; }
max_size(log_id_t id)63     unsigned long max_size(log_id_t id) REQUIRES_SHARED(lock_) { return max_size_[id]; }
logs()64     std::list<LogBufferElement>& logs() { return logs_; }
65 
66     RwLock lock_;
67 
68   private:
69     bool ShouldLog(log_id_t log_id, const char* msg, uint16_t len);
70     void MaybePrune(log_id_t id) REQUIRES(lock_);
71 
72     LogReaderList* reader_list_;
73     LogTags* tags_;
74     LogStatistics* stats_;
75 
76     std::atomic<uint64_t> sequence_ = 1;
77 
78     unsigned long max_size_[LOG_ID_MAX] GUARDED_BY(lock_);
79     std::list<LogBufferElement> logs_ GUARDED_BY(lock_);
80     // Keeps track of the iterator to the oldest log message of a given log type, as an
81     // optimization when pruning logs.  Use GetOldest() to retrieve.
82     std::optional<std::list<LogBufferElement>::iterator> oldest_[LOG_ID_MAX] GUARDED_BY(lock_);
83 };
84