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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
/*
* Ceph - scalable distributed file system
*
* Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
*
* This is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 2.1, as published by the Free Software
* Foundation. See file COPYING.
*
*/
#ifndef CEPH_COMMON_MUTEX_DEBUG_H
#define CEPH_COMMON_MUTEX_DEBUG_H
#include <atomic>
#include <system_error>
#include <thread>
#include <pthread.h>
#include "include/ceph_assert.h"
#include "include/common_fwd.h"
#include "ceph_time.h"
#include "likely.h"
#include "lockdep.h"
namespace ceph {
namespace mutex_debug_detail {
class mutex_debugging_base
{
protected:
std::string group;
int id = -1;
bool lockdep; // track this mutex using lockdep_*
bool backtrace; // gather backtrace on lock acquisition
std::atomic<int> nlock = 0;
std::thread::id locked_by = {};
bool _enable_lockdep() const {
return lockdep && g_lockdep;
}
void _register();
void _will_lock(bool recursive=false); // about to lock
void _locked(); // just locked
void _will_unlock(); // about to unlock
mutex_debugging_base(std::string group, bool ld = true, bool bt = false);
~mutex_debugging_base();
public:
bool is_locked() const {
return (nlock > 0);
}
bool is_locked_by_me() const {
return nlock.load(std::memory_order_acquire) > 0 && locked_by == std::this_thread::get_id();
}
operator bool() const {
return is_locked_by_me();
}
};
// Since this is a /debugging/ mutex just define it in terms of the
// pthread error check mutex.
template<bool Recursive>
class mutex_debug_impl : public mutex_debugging_base
{
private:
pthread_mutex_t m;
void _init() {
pthread_mutexattr_t a;
pthread_mutexattr_init(&a);
int r;
if (recursive)
r = pthread_mutexattr_settype(&a, PTHREAD_MUTEX_RECURSIVE);
else
r = pthread_mutexattr_settype(&a, PTHREAD_MUTEX_ERRORCHECK);
ceph_assert(r == 0);
r = pthread_mutex_init(&m, &a);
ceph_assert(r == 0);
}
bool enable_lockdep(bool no_lockdep) const {
if (recursive) {
return false;
} else if (no_lockdep) {
return false;
} else {
return _enable_lockdep();
}
}
public:
static constexpr bool recursive = Recursive;
mutex_debug_impl(std::string group, bool ld = true, bool bt = false)
: mutex_debugging_base(group, ld, bt) {
_init();
}
// Mutex is Destructible
~mutex_debug_impl() {
int r = pthread_mutex_destroy(&m);
ceph_assert(r == 0);
}
// Mutex concept is non-Copyable
mutex_debug_impl(const mutex_debug_impl&) = delete;
mutex_debug_impl& operator =(const mutex_debug_impl&) = delete;
// Mutex concept is non-Movable
mutex_debug_impl(mutex_debug_impl&&) = delete;
mutex_debug_impl& operator =(mutex_debug_impl&&) = delete;
void lock_impl() {
int r = pthread_mutex_lock(&m);
// Allowed error codes for Mutex concept
if (unlikely(r == EPERM ||
r == EDEADLK ||
r == EBUSY)) {
throw std::system_error(r, std::generic_category());
}
ceph_assert(r == 0);
}
void unlock_impl() noexcept {
int r = pthread_mutex_unlock(&m);
ceph_assert(r == 0);
}
bool try_lock_impl() {
int r = pthread_mutex_trylock(&m);
switch (r) {
case 0:
return true;
case EBUSY:
return false;
default:
throw std::system_error(r, std::generic_category());
}
}
pthread_mutex_t* native_handle() {
return &m;
}
void _post_lock() {
if (!recursive)
ceph_assert(nlock == 0);
locked_by = std::this_thread::get_id();
nlock.fetch_add(1, std::memory_order_release);
}
void _pre_unlock() {
if (recursive) {
ceph_assert(nlock > 0);
} else {
ceph_assert(nlock == 1);
}
ceph_assert(locked_by == std::this_thread::get_id());
if (nlock == 1)
locked_by = std::thread::id();
nlock.fetch_sub(1, std::memory_order_release);
}
bool try_lock(bool no_lockdep = false) {
bool locked = try_lock_impl();
if (locked) {
if (enable_lockdep(no_lockdep))
_locked();
_post_lock();
}
return locked;
}
void lock(bool no_lockdep = false) {
if (enable_lockdep(no_lockdep))
_will_lock(recursive);
if (try_lock(no_lockdep))
return;
lock_impl();
if (enable_lockdep(no_lockdep))
_locked();
_post_lock();
}
void unlock(bool no_lockdep = false) {
_pre_unlock();
if (enable_lockdep(no_lockdep))
_will_unlock();
unlock_impl();
}
};
} // namespace mutex_debug_detail
typedef mutex_debug_detail::mutex_debug_impl<false> mutex_debug;
typedef mutex_debug_detail::mutex_debug_impl<true> mutex_recursive_debug;
} // namespace ceph
#endif
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