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https://github.com/oxen-io/lokinet.git
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b4440094b0
- util::Mutex is now a std::shared_timed_mutex, which is capable of
exclusive and shared locks.
- util::Lock is still present as a std::lock_guard<util::Mutex>.
- the locking annotations are preserved, but updated to the latest
supported by clang rather than using abseil's older/deprecated ones.
- ACQUIRE_LOCK macro is gone since we don't pass mutexes by pointer into
locks anymore (WTF abseil).
- ReleasableLock is gone. Instead there are now some llarp::util helper
methods to obtain unique and/or shared locks:
- `auto lock = util::unique_lock(mutex);` gets an RAII-but-also
unlockable object (std::unique_lock<T>, with T inferred from
`mutex`).
- `auto lock = util::shared_lock(mutex);` gets an RAII shared (i.e.
"reader") lock of the mutex.
- `auto lock = util::unique_locks(mutex1, mutex2, mutex3);` can be
used to atomically lock multiple mutexes at once (returning a
tuple of the locks).
This are templated on the mutex which makes them a bit more flexible
than using a concrete type: they can be used for any type of lockable
mutex, not only util::Mutex. (Some of the code here uses them for
getting locks around a std::mutex). Until C++17, using the RAII types
is painfully verbose:
```C++
// pre-C++17 - needing to figure out the mutex type here is annoying:
std::unique_lock<util::Mutex> lock(mutex);
// pre-C++17 and even more verbose (but at least the type isn't needed):
std::unique_lock<decltype(mutex)> lock(mutex);
// our compromise:
auto lock = util::unique_lock(mutex);
// C++17:
std::unique_lock lock(mutex);
```
All of these functions will also warn (under gcc or clang) if you
discard the return value. You can also do fancy things like
`auto l = util::unique_lock(mutex, std::adopt_lock)` (which lets a
lock take over an already-locked mutex).
- metrics code is gone, which also removes a big pile of code that was
only used by metrics:
- llarp::util::Scheduler
- llarp:🧵:TimerQueue
- llarp::util::Stopwatch
47 lines
1.0 KiB
C++
47 lines
1.0 KiB
C++
#pragma once
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#include <mutex>
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#include <condition_variable>
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namespace llarp
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{
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namespace util
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{
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/// Barrier class that blocks all threads until the high water mark of
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/// threads (set during construction) is reached, then releases them all.
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class Barrier
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{
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std::mutex mutex;
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std::condition_variable cv;
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unsigned pending;
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public:
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Barrier(unsigned threads) : pending{threads}
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{
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}
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/// Returns true if *this* Block call is the one that releases all of
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/// them; returns false (i.e. after unblocking) if some other thread
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/// triggered the released.
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bool
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Block()
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{
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std::unique_lock< std::mutex > lock{mutex};
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if(pending == 1)
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{
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pending = 0;
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lock.unlock();
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cv.notify_all();
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return true;
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}
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else if(pending > 1)
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{
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pending--;
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}
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cv.wait(lock, [this] { return !pending; });
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return false;
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}
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};
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} // namespace util
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} // namespace llarp
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