ReadWriteLock.h
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1/*
2 * Copyright (C) 1996-2023 The Squid Software Foundation and contributors
3 *
4 * Squid software is distributed under GPLv2+ license and includes
5 * contributions from numerous individuals and organizations.
6 * Please see the COPYING and CONTRIBUTORS files for details.
7 */
8
9#ifndef SQUID_IPC_READ_WRITE_LOCK_H
10#define SQUID_IPC_READ_WRITE_LOCK_H
11
12#include <atomic>
13#include <iosfwd>
14
15class StoreEntry;
16
17namespace Ipc
18{
19
20class ReadWriteLockStats;
21
27{
28public:
30 {}
31
32 bool lockShared();
33 bool lockExclusive();
34 bool lockHeaders();
35 void unlockShared();
36 void unlockExclusive();
37 void unlockHeaders();
42
43 void startAppending();
44
47
48public:
49 mutable std::atomic<uint32_t> readers;
50 std::atomic<bool> writing;
51 std::atomic<bool> appending;
52 std::atomic_flag updating;
53
54private:
55 bool finalizeExclusive();
56
57 mutable std::atomic<uint32_t> readLevel;
58 std::atomic<uint32_t> writeLevel;
59};
60
62std::ostream &operator <<(std::ostream &, const ReadWriteLock &);
63
66{
67public:
69
70 void dump(StoreEntry &e) const;
71
72 int count;
75 int idle;
76 int readers;
77 int writers;
79};
80
84void AssertFlagIsSet(std::atomic_flag &flag);
85
86} // namespace Ipc
87
88#endif /* SQUID_IPC_READ_WRITE_LOCK_H */
89
approximate stats of a set of ReadWriteLocks
Definition: ReadWriteLock.h:66
int readable
number of locks locked for reading
Definition: ReadWriteLock.h:73
int idle
number of unlocked locks
Definition: ReadWriteLock.h:75
int writers
sum of lock.writers
Definition: ReadWriteLock.h:77
int count
the total number of locks
Definition: ReadWriteLock.h:72
void dump(StoreEntry &e) const
int writeable
number of locks locked for writing
Definition: ReadWriteLock.h:74
int readers
sum of lock.readers
Definition: ReadWriteLock.h:76
int appenders
number of appending writers
Definition: ReadWriteLock.h:78
void unlockHeaders()
undo successful lockHeaders()
std::atomic< uint32_t > readLevel
number of users reading (or trying to)
Definition: ReadWriteLock.h:57
void switchExclusiveToShared()
bool lockHeaders()
lock for [readable] metadata update or return false
std::atomic< uint32_t > readers
number of reading users
Definition: ReadWriteLock.h:49
void unlockExclusive()
undo successful exclusiveLock()
bool lockExclusive()
lock for modification or return false
std::atomic_flag updating
a reader is updating metadata/headers
Definition: ReadWriteLock.h:52
std::atomic< uint32_t > writeLevel
number of users writing (or trying to write)
Definition: ReadWriteLock.h:58
std::atomic< bool > writing
there is a writing user (there can be at most 1)
Definition: ReadWriteLock.h:50
bool unlockSharedAndSwitchToExclusive()
std::atomic< bool > appending
the writer has promised to only append
Definition: ReadWriteLock.h:51
void unlockShared()
undo successful sharedLock()
bool lockShared()
lock for reading or return false
void updateStats(ReadWriteLockStats &stats) const
adds approximate current stats to the supplied ones
void startAppending()
writer keeps its lock but also allows reading
Definition: IpcIoFile.h:24
void AssertFlagIsSet(std::atomic_flag &flag)
std::ostream & operator<<(std::ostream &os, const QuestionerId &qid)
Definition: QuestionerId.h:63
class Ping::pingStats_ stats

 

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