ecency-mobile/ios/Pods/boost-for-react-native/boost/interprocess/detail/robust_emulation.hpp

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//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2010-2012. Distributed under the Boost
// Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/interprocess for documentation.
//
//////////////////////////////////////////////////////////////////////////////
#ifndef BOOST_INTERPROCESS_ROBUST_EMULATION_HPP
#define BOOST_INTERPROCESS_ROBUST_EMULATION_HPP
#ifndef BOOST_CONFIG_HPP
# include <boost/config.hpp>
#endif
#
#if defined(BOOST_HAS_PRAGMA_ONCE)
#pragma once
#endif
#include <boost/interprocess/detail/config_begin.hpp>
#include <boost/interprocess/detail/workaround.hpp>
#include <boost/interprocess/sync/interprocess_mutex.hpp>
#include <boost/interprocess/sync/interprocess_recursive_mutex.hpp>
#include <boost/interprocess/detail/atomic.hpp>
#include <boost/interprocess/detail/os_file_functions.hpp>
#include <boost/interprocess/detail/shared_dir_helpers.hpp>
#include <boost/interprocess/detail/intermodule_singleton.hpp>
#include <boost/interprocess/detail/portable_intermodule_singleton.hpp>
#include <boost/interprocess/exceptions.hpp>
#include <boost/interprocess/sync/spin/wait.hpp>
#include <boost/interprocess/sync/detail/common_algorithms.hpp>
#include <string>
namespace boost{
namespace interprocess{
namespace ipcdetail{
namespace robust_emulation_helpers {
template<class T>
class mutex_traits
{
public:
static void take_ownership(T &t)
{ t.take_ownership(); }
};
inline void remove_if_can_lock_file(const char *file_path)
{
file_handle_t fhnd = open_existing_file(file_path, read_write);
if(fhnd != invalid_file()){
bool acquired;
if(try_acquire_file_lock(fhnd, acquired) && acquired){
delete_file(file_path);
}
close_file(fhnd);
}
}
inline const char *robust_lock_subdir_path()
{ return "robust"; }
inline const char *robust_lock_prefix()
{ return "lck"; }
inline void robust_lock_path(std::string &s)
{
get_shared_dir(s);
s += "/";
s += robust_lock_subdir_path();
}
inline void create_and_get_robust_lock_file_path(std::string &s, OS_process_id_t pid)
{
intermodule_singleton_helpers::create_tmp_subdir_and_get_pid_based_filepath
(robust_lock_subdir_path(), robust_lock_prefix(), pid, s);
}
//This class will be a intermodule_singleton. The constructor will create
//a lock file, the destructor will erase it.
//
//We should take in care that another process might be erasing unlocked
//files while creating this one, so there are some race conditions we must
//take in care to guarantee some robustness.
class robust_mutex_lock_file
{
file_handle_t fd;
std::string fname;
public:
robust_mutex_lock_file()
{
permissions p;
p.set_unrestricted();
//Remove old lock files of other processes
remove_old_robust_lock_files();
//Create path and obtain lock file path for this process
create_and_get_robust_lock_file_path(fname, get_current_process_id());
//Now try to open or create the lock file
fd = create_or_open_file(fname.c_str(), read_write, p);
//If we can't open or create it, then something unrecoverable has happened
if(fd == invalid_file()){
throw interprocess_exception(other_error, "Robust emulation robust_mutex_lock_file constructor failed: could not open or create file");
}
//Now we must take in care a race condition with another process
//calling "remove_old_robust_lock_files()". No other threads from this
//process will be creating the lock file because intermodule_singleton
//guarantees this. So let's loop acquiring the lock and checking if we
//can't exclusively create the file (if the file is erased by another process
//then this exclusive open would fail). If the file can't be exclusively created
//then we have correctly open/create and lock the file. If the file can
//be exclusively created, then close previous locked file and try again.
while(1){
bool acquired;
if(!try_acquire_file_lock(fd, acquired) || !acquired ){
throw interprocess_exception(other_error, "Robust emulation robust_mutex_lock_file constructor failed: try_acquire_file_lock");
}
//Creating exclusively must fail with already_exists_error
//to make sure we've locked the file and no one has
//deleted it between creation and locking
file_handle_t fd2 = create_new_file(fname.c_str(), read_write, p);
if(fd2 != invalid_file()){
close_file(fd);
fd = fd2;
continue;
}
//If exclusive creation fails with expected error go ahead
else if(error_info(system_error_code()).get_error_code() == already_exists_error){ //must already exist
//Leak descriptor to mantain the file locked until the process dies
break;
}
//If exclusive creation fails with unexpected error throw an unrecoverable error
else{
close_file(fd);
throw interprocess_exception(other_error, "Robust emulation robust_mutex_lock_file constructor failed: create_file filed with unexpected error");
}
}
}
~robust_mutex_lock_file()
{
//The destructor is guaranteed by intermodule_singleton to be
//executed serialized between all threads from current process,
//so we just need to close and unlink the file.
close_file(fd);
//If some other process deletes the file before us after
//closing it there should not be any problem.
delete_file(fname.c_str());
}
private:
//This functor is execute for all files in the lock file directory
class other_process_lock_remover
{
public:
void operator()(const char *filepath, const char *filename)
{
std::string pid_str;
//If the lock file is not our own lock file, then try to do the cleanup
if(!intermodule_singleton_helpers::check_if_filename_complies_with_pid
(filename, robust_lock_prefix(), get_current_process_id(), pid_str)){
remove_if_can_lock_file(filepath);
}
}
};
bool remove_old_robust_lock_files()
{
std::string refcstrRootDirectory;
robust_lock_path(refcstrRootDirectory);
return for_each_file_in_dir(refcstrRootDirectory.c_str(), other_process_lock_remover());
}
};
} //namespace robust_emulation_helpers {
//This is the mutex class. Mutex should follow mutex concept
//with an additonal "take_ownership()" function to take ownership of the
//mutex when robust_spin_mutex determines the previous owner was dead.
template<class Mutex>
class robust_spin_mutex
{
public:
static const boost::uint32_t correct_state = 0;
static const boost::uint32_t fixing_state = 1;
static const boost::uint32_t broken_state = 2;
typedef robust_emulation_helpers::mutex_traits<Mutex> mutex_traits_t;
robust_spin_mutex();
void lock();
bool try_lock();
bool timed_lock(const boost::posix_time::ptime &abs_time);
void unlock();
void consistent();
bool previous_owner_dead();
private:
static const unsigned int spin_threshold = 100u;
bool lock_own_unique_file();
bool robust_check();
bool check_if_owner_dead_and_take_ownership_atomically();
bool is_owner_dead(boost::uint32_t own);
void owner_to_filename(boost::uint32_t own, std::string &s);
//The real mutex
Mutex mtx;
//The pid of the owner
volatile boost::uint32_t owner;
//The state of the mutex (correct, fixing, broken)
volatile boost::uint32_t state;
};
template<class Mutex>
inline robust_spin_mutex<Mutex>::robust_spin_mutex()
: mtx(), owner(get_invalid_process_id()), state(correct_state)
{}
template<class Mutex>
inline void robust_spin_mutex<Mutex>::lock()
{ try_based_lock(*this); }
template<class Mutex>
inline bool robust_spin_mutex<Mutex>::try_lock()
{
//Same as lock() but without spinning
if(atomic_read32(&this->state) == broken_state){
throw interprocess_exception(lock_error, "Broken id");
}
if(!this->lock_own_unique_file()){
throw interprocess_exception(lock_error, "Broken id");
}
if (mtx.try_lock()){
atomic_write32(&this->owner, get_current_process_id());
return true;
}
else{
if(!this->robust_check()){
return false;
}
else{
return true;
}
}
}
template<class Mutex>
inline bool robust_spin_mutex<Mutex>::timed_lock
(const boost::posix_time::ptime &abs_time)
{ return try_based_timed_lock(*this, abs_time); }
template<class Mutex>
inline void robust_spin_mutex<Mutex>::owner_to_filename(boost::uint32_t own, std::string &s)
{
robust_emulation_helpers::create_and_get_robust_lock_file_path(s, own);
}
template<class Mutex>
inline bool robust_spin_mutex<Mutex>::robust_check()
{
//If the old owner was dead, and we've acquired ownership, mark
//the mutex as 'fixing'. This means that a "consistent()" is needed
//to avoid marking the mutex as "broken" when the mutex is unlocked.
if(!this->check_if_owner_dead_and_take_ownership_atomically()){
return false;
}
atomic_write32(&this->state, fixing_state);
return true;
}
template<class Mutex>
inline bool robust_spin_mutex<Mutex>::check_if_owner_dead_and_take_ownership_atomically()
{
boost::uint32_t cur_owner = get_current_process_id();
boost::uint32_t old_owner = atomic_read32(&this->owner), old_owner2;
//The cas loop guarantees that only one thread from this or another process
//will succeed taking ownership
do{
//Check if owner is dead
if(!this->is_owner_dead(old_owner)){
return false;
}
//If it's dead, try to mark this process as the owner in the owner field
old_owner2 = old_owner;
old_owner = atomic_cas32(&this->owner, cur_owner, old_owner);
}while(old_owner2 != old_owner);
//If success, we fix mutex internals to assure our ownership
mutex_traits_t::take_ownership(mtx);
return true;
}
template<class Mutex>
inline bool robust_spin_mutex<Mutex>::is_owner_dead(boost::uint32_t own)
{
//If owner is an invalid id, then it's clear it's dead
if(own == (boost::uint32_t)get_invalid_process_id()){
return true;
}
//Obtain the lock filename of the owner field
std::string file;
this->owner_to_filename(own, file);
//Now the logic is to open and lock it
file_handle_t fhnd = open_existing_file(file.c_str(), read_write);
if(fhnd != invalid_file()){
//If we can open the file, lock it.
bool acquired;
if(try_acquire_file_lock(fhnd, acquired) && acquired){
//If locked, just delete the file
delete_file(file.c_str());
close_file(fhnd);
return true;
}
//If not locked, the owner is suppossed to be still alive
close_file(fhnd);
}
else{
//If the lock file does not exist then the owner is dead (a previous cleanup)
//function has deleted the file. If there is another reason, then this is
//an unrecoverable error
if(error_info(system_error_code()).get_error_code() == not_found_error){
return true;
}
}
return false;
}
template<class Mutex>
inline void robust_spin_mutex<Mutex>::consistent()
{
//This function supposes the previous state was "fixing"
//and the current process holds the mutex
if(atomic_read32(&this->state) != fixing_state &&
atomic_read32(&this->owner) != (boost::uint32_t)get_current_process_id()){
throw interprocess_exception(lock_error, "Broken id");
}
//If that's the case, just update mutex state
atomic_write32(&this->state, correct_state);
}
template<class Mutex>
inline bool robust_spin_mutex<Mutex>::previous_owner_dead()
{
//Notifies if a owner recovery has been performed in the last lock()
return atomic_read32(&this->state) == fixing_state;
}
template<class Mutex>
inline void robust_spin_mutex<Mutex>::unlock()
{
//If in "fixing" state, unlock and mark the mutex as unrecoverable
//so next locks will fail and all threads will be notified that the
//data protected by the mutex was not recoverable.
if(atomic_read32(&this->state) == fixing_state){
atomic_write32(&this->state, broken_state);
}
//Write an invalid owner to minimize pid reuse possibility
atomic_write32(&this->owner, get_invalid_process_id());
mtx.unlock();
}
template<class Mutex>
inline bool robust_spin_mutex<Mutex>::lock_own_unique_file()
{
//This function forces instantiation of the singleton
robust_emulation_helpers::robust_mutex_lock_file* dummy =
&ipcdetail::intermodule_singleton
<robust_emulation_helpers::robust_mutex_lock_file>::get();
return dummy != 0;
}
} //namespace ipcdetail{
} //namespace interprocess{
} //namespace boost{
#include <boost/interprocess/detail/config_end.hpp>
#endif