Adding upstream version 18.2.2.upstream/18.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 393 insertions, 0 deletions

diff --git a/src/common/shunique_lock.h b/src/common/shunique_lock.h
new file mode 100644
index 000000000..5f809e83a
--- /dev/null
+++ b/src/common/shunique_lock.h
@@ -0,0 +1,393 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#ifndef CEPH_COMMON_SHUNIQUE_LOCK_H
+#define CEPH_COMMON_SHUNIQUE_LOCK_H
+
+#include <mutex>
+#include <shared_mutex>
+#include <system_error>
+
+namespace ceph {
+// This is a 'lock' class in the style of shared_lock and
+// unique_lock. Like shared_mutex it implements both Lockable and
+// SharedLockable.
+
+// My rationale is thus: one of the advantages of unique_lock is that
+// I can pass a thread of execution's control of a lock around as a
+// parameter. So that methods further down the call stack can unlock
+// it, do something, relock it, and have the lock state be known by
+// the caller afterward, explicitly. The shared_lock class offers a
+// similar advantage to shared_lock, but each class is one or the
+// other. In Objecter we have calls that in most cases need /a/ lock
+// on the shared mutex, and whether it's shared or exclusive doesn't
+// matter. In some circumstances they may drop the shared lock and
+// reacquire an exclusive one. This could be handled by passing both a
+// shared and unique lock down the call stack. This is vexacious and
+// shameful.
+
+// Wanting to avoid heaping shame and vexation upon myself, I threw
+// this class together.
+
+// This class makes no attempt to support atomic upgrade or
+// downgrade. I don't want either. Matt has convinced me that if you
+// think you want them you've usually made a mistake somewhere. It is
+// exactly and only a reification of the state held on a shared mutex.
+
+/// Acquire unique ownership of the mutex.
+struct acquire_unique_t { };
+
+/// Acquire shared ownership of the mutex.
+struct acquire_shared_t { };
+
+constexpr acquire_unique_t acquire_unique { };
+constexpr acquire_shared_t acquire_shared { };
+
+template<typename Mutex>
+class shunique_lock {
+public:
+  typedef Mutex mutex_type;
+  typedef std::unique_lock<Mutex> unique_lock_type;
+  typedef std::shared_lock<Mutex> shared_lock_type;
+
+  shunique_lock() noexcept : m(nullptr), o(ownership::none) { }
+
+  // We do not provide a default locking/try_locking constructor that
+  // takes only the mutex, since it is not clear whether to take it
+  // shared or unique. We explicitly require the use of lock_deferred
+  // to prevent Nasty Surprises.
+
+  shunique_lock(mutex_type& m, std::defer_lock_t) noexcept
+    : m(&m), o(ownership::none) { }
+
+  shunique_lock(mutex_type& m, acquire_unique_t)
+    : m(&m), o(ownership::none) {
+    lock();
+  }
+
+  shunique_lock(mutex_type& m, acquire_shared_t)
+    : m(&m), o(ownership::none) {
+    lock_shared();
+  }
+
+  template<typename AcquireType>
+  shunique_lock(mutex_type& m, AcquireType at, std::try_to_lock_t)
+    : m(&m), o(ownership::none) {
+    try_lock(at);
+  }
+
+  shunique_lock(mutex_type& m, acquire_unique_t, std::adopt_lock_t)
+    : m(&m), o(ownership::unique) {
+    // You'd better actually have a lock, or I will find you and I
+    // will hunt you down.
+  }
+
+  shunique_lock(mutex_type& m, acquire_shared_t, std::adopt_lock_t)
+    : m(&m), o(ownership::shared) {
+  }
+
+  template<typename AcquireType, typename Clock, typename Duration>
+  shunique_lock(mutex_type& m, AcquireType at,
+		const std::chrono::time_point<Clock, Duration>& t)
+    : m(&m), o(ownership::none) {
+    try_lock_until(at, t);
+  }
+
+  template<typename AcquireType, typename Rep, typename Period>
+  shunique_lock(mutex_type& m, AcquireType at,
+		const std::chrono::duration<Rep, Period>& dur)
+    : m(&m), o(ownership::none) {
+    try_lock_for(at, dur);
+  }
+
+  ~shunique_lock() {
+    switch (o) {
+    case ownership::none:
+      return;
+    case ownership::unique:
+      m->unlock();
+      break;
+    case ownership::shared:
+      m->unlock_shared();
+      break;
+    }
+  }
+
+  shunique_lock(shunique_lock const&) = delete;
+  shunique_lock& operator=(shunique_lock const&) = delete;
+
+  shunique_lock(shunique_lock&& l) noexcept : shunique_lock() {
+    swap(l);
+  }
+
+  shunique_lock(unique_lock_type&& l) noexcept {
+    if (l.owns_lock())
+      o = ownership::unique;
+    else
+      o = ownership::none;
+    m = l.release();
+  }
+
+  shunique_lock(shared_lock_type&& l) noexcept {
+    if (l.owns_lock())
+      o = ownership::shared;
+    else
+      o = ownership::none;
+    m = l.release();
+  }
+
+  shunique_lock& operator=(shunique_lock&& l) noexcept {
+    shunique_lock(std::move(l)).swap(*this);
+    return *this;
+  }
+
+  shunique_lock& operator=(unique_lock_type&& l) noexcept {
+    shunique_lock(std::move(l)).swap(*this);
+    return *this;
+  }
+
+  shunique_lock& operator=(shared_lock_type&& l) noexcept {
+    shunique_lock(std::move(l)).swap(*this);
+    return *this;
+  }
+
+  void lock() {
+    lockable();
+    m->lock();
+    o = ownership::unique;
+  }
+
+  void lock_shared() {
+    lockable();
+    m->lock_shared();
+    o = ownership::shared;
+  }
+
+  void lock(ceph::acquire_unique_t) {
+    lock();
+  }
+
+  void lock(ceph::acquire_shared_t) {
+    lock_shared();
+  }
+
+  bool try_lock() {
+    lockable();
+    if (m->try_lock()) {
+      o = ownership::unique;
+      return true;
+    }
+    return false;
+  }
+
+  bool try_lock_shared() {
+    lockable();
+    if (m->try_lock_shared()) {
+      o = ownership::shared;
+      return true;
+    }
+    return false;
+  }
+
+  bool try_lock(ceph::acquire_unique_t) {
+    return try_lock();
+  }
+
+  bool try_lock(ceph::acquire_shared_t) {
+    return try_lock_shared();
+  }
+
+  template<typename Rep, typename Period>
+  bool try_lock_for(const std::chrono::duration<Rep, Period>& dur) {
+    lockable();
+    if (m->try_lock_for(dur)) {
+      o = ownership::unique;
+      return true;
+    }
+    return false;
+  }
+
+  template<typename Rep, typename Period>
+  bool try_lock_shared_for(const std::chrono::duration<Rep, Period>& dur) {
+    lockable();
+    if (m->try_lock_shared_for(dur)) {
+      o = ownership::shared;
+      return true;
+    }
+    return false;
+  }
+
+  template<typename Rep, typename Period>
+  bool try_lock_for(ceph::acquire_unique_t,
+		    const std::chrono::duration<Rep, Period>& dur) {
+    return try_lock_for(dur);
+  }
+
+  template<typename Rep, typename Period>
+  bool try_lock_for(ceph::acquire_shared_t,
+		    const std::chrono::duration<Rep, Period>& dur) {
+    return try_lock_shared_for(dur);
+  }
+
+  template<typename Clock, typename Duration>
+  bool try_lock_until(const std::chrono::time_point<Clock, Duration>& time) {
+    lockable();
+    if (m->try_lock_until(time)) {
+      o = ownership::unique;
+      return true;
+    }
+    return false;
+  }
+
+  template<typename Clock, typename Duration>
+  bool try_lock_shared_until(const std::chrono::time_point<Clock,
+			     Duration>& time) {
+    lockable();
+    if (m->try_lock_shared_until(time)) {
+      o = ownership::shared;
+      return true;
+    }
+    return false;
+  }
+
+  template<typename Clock, typename Duration>
+  bool try_lock_until(ceph::acquire_unique_t,
+		      const std::chrono::time_point<Clock, Duration>& time) {
+    return try_lock_until(time);
+  }
+
+  template<typename Clock, typename Duration>
+  bool try_lock_until(ceph::acquire_shared_t,
+		      const std::chrono::time_point<Clock, Duration>& time) {
+    return try_lock_shared_until(time);
+  }
+
+  // Only have a single unlock method. Otherwise we'd be building an
+  // Acme lock class suitable only for ravenous coyotes desparate to
+  // devour a road runner. It would be bad. It would be disgusting. It
+  // would be infelicitous as heck. It would leave our developers in a
+  // state of seeming safety unaware of the yawning chasm of failure
+  // that had opened beneath their feet that would soon transition
+  // into a sickening realization of the error they made and a brief
+  // moment of blinking self pity before their program hurled itself
+  // into undefined behaviour and plummeted up the stack with core
+  // dumps trailing behind it.
+
+  void unlock() {
+    switch (o) {
+    case ownership::none:
+      throw std::system_error((int)std::errc::resource_deadlock_would_occur,
+			      std::generic_category());
+      break;
+
+    case ownership::unique:
+      m->unlock();
+      break;
+
+    case ownership::shared:
+      m->unlock_shared();
+      break;
+    }
+    o = ownership::none;
+  }
+
+  // Setters
+
+  void swap(shunique_lock& u) noexcept {
+    std::swap(m, u.m);
+    std::swap(o, u.o);
+  }
+
+  mutex_type* release() noexcept {
+    o = ownership::none;
+    mutex_type* tm = m;
+    m = nullptr;
+    return tm;
+  }
+
+  // Ideally I'd rather make a move constructor for std::unique_lock
+  // that took a shunique_lock, but obviously I can't.
+  unique_lock_type release_to_unique() {
+    if (o == ownership::unique) {
+      o = ownership::none;
+      unique_lock_type tu(*m, std::adopt_lock);
+      m = nullptr;
+      return tu;
+    } else if (o == ownership::none) {
+      unique_lock_type tu(*m, std::defer_lock);
+      m = nullptr;
+      return tu;
+    } else if (m == nullptr) {
+      return unique_lock_type();
+    }
+    throw std::system_error((int)std::errc::operation_not_permitted,
+			    std::generic_category());
+  }
+
+  shared_lock_type release_to_shared() {
+    if (o == ownership::shared) {
+      o = ownership::none;
+      shared_lock_type ts(*m, std::adopt_lock);
+      m = nullptr;
+      return ts;
+    } else if (o == ownership::none) {
+      shared_lock_type ts(*m, std::defer_lock);
+      m = nullptr;
+      return ts;
+    } else if (m == nullptr) {
+      return shared_lock_type();
+    }
+    throw std::system_error((int)std::errc::operation_not_permitted,
+			    std::generic_category());
+    return shared_lock_type();
+  }
+
+  // Getters
+
+  // Note that this returns true if the lock UNIQUE, it will return
+  // false for shared
+  bool owns_lock() const noexcept {
+    return o == ownership::unique;
+  }
+
+  bool owns_lock_shared() const noexcept {
+    return o == ownership::shared;
+  }
+
+  // If you want to make sure you have a lock of some sort on the
+  // mutex, just treat as a bool.
+  explicit operator bool() const noexcept {
+    return o != ownership::none;
+  }
+
+  mutex_type* mutex() const noexcept {
+    return m;
+  }
+
+private:
+  void lockable() const {
+    if (m == nullptr)
+      throw std::system_error((int)std::errc::operation_not_permitted,
+			      std::generic_category());
+    if (o != ownership::none)
+      throw std::system_error((int)std::errc::resource_deadlock_would_occur,
+			      std::generic_category());
+  }
+
+  mutex_type*	m;
+  enum struct ownership : uint8_t {
+    none, unique, shared
+      };
+  ownership o;
+};
+} // namespace ceph
+
+namespace std {
+  template<typename Mutex>
+  void swap(ceph::shunique_lock<Mutex> sh1,
+	    ceph::shunique_lock<Mutex> sha) {
+    sh1.swap(sha);
+  }
+} // namespace std
+
+#endif // CEPH_COMMON_SHUNIQUE_LOCK_H