Subject: [Boost-commit] svn:boost r64337 - trunk/boost/interprocess/detail
From: igaztanaga_at_[hidden]
Date: 2010-07-25 12:47:46
Author: igaztanaga
Date: 2010-07-25 12:47:46 EDT (Sun, 25 Jul 2010)
New Revision: 64337
URL: http://svn.boost.org/trac/boost/changeset/64337
Log:
Changes for Boost 1.45
Text files modified:
trunk/boost/interprocess/detail/intermodule_singleton.hpp | 496 +++++++++++++++++++++++++--------------
1 files changed, 317 insertions(+), 179 deletions(-)
Modified: trunk/boost/interprocess/detail/intermodule_singleton.hpp
==============================================================================
--- trunk/boost/interprocess/detail/intermodule_singleton.hpp (original)
+++ trunk/boost/interprocess/detail/intermodule_singleton.hpp 2010-07-25 12:47:46 EDT (Sun, 25 Jul 2010)
@@ -24,11 +24,12 @@
#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/detail/tmp_dir_helpers.hpp>
#include <boost/interprocess/detail/os_file_functions.hpp>
-#include <boost/interprocess/streams/bufferstream.hpp>
+#include <boost/interprocess/detail/mpl.hpp>
#include <cassert>
#include <cstddef>
#include <cstdio>
#include <cstring>
+#include <string>
#include <sys/types.h>
#include <sys/stat.h>
@@ -49,57 +50,96 @@
namespace interprocess{
namespace detail{
-namespace intermodule_singleton_helpers {
-
-const int GMemMarkToBeRemoved = -1;
-const int GMemNotPresent = -2;
-
-typedef char pid_str_t[sizeof(OS_process_id_t)*3+1];
+namespace file_locking_helpers {
-inline void get_pid_str(pid_str_t &pid_str)
+inline void get_pid_creation_time_str(std::string &s)
{
- OS_process_id_t pid = get_current_process_id();
- bufferstream bstream(pid_str, sizeof(pid_str));
- bstream << pid << std::ends;
+ std::stringstream stream;
+ stream << get_current_process_id() << '_';
+ stream.precision(6);
+ stream << std::fixed << get_current_process_creation_time();
+ s = stream.str();
}
-inline const char *get_lock_file_base_name()
-{ return "bip.gmem.lock."; }
-
-inline const char *get_lock_file_subdir_name()
-{ return "bip.gmem.locks"; }
-
-inline void create_and_get_lock_file_path(std::string &s)
+inline void create_tmp_subdir_and_get_pid_based_filepath(const char *subdir_name, const char *file_prefix, OS_process_id_t pid, std::string &s, bool creation_time = false)
{
- std::string filename(get_lock_file_base_name());
- pid_str_t pid_str;
- get_pid_str(pid_str);
- filename += pid_str;
- tmp_folder(s);
- if(!open_or_create_directory(s.c_str())){
- throw interprocess_exception(error_info(system_error_code()));
- }
+ //Let's create a lock file for each process gmem that will mark if
+ //the process is alive or not
+ create_tmp_and_clean_old(s);
s += "/";
- s += get_lock_file_subdir_name();
+ s += subdir_name;
if(!open_or_create_directory(s.c_str())){
throw interprocess_exception(error_info(system_error_code()));
}
s += "/";
- s += filename;
+ s += file_prefix;
+ if(creation_time){
+ std::string sstamp;
+ get_pid_creation_time_str(sstamp);
+ s += sstamp;
+ }
+ else{
+ pid_str_t pid_str;
+ get_pid_str(pid_str, pid);
+ s += pid_str;
+ }
}
-inline void get_lock_file_path(std::string &s)
-{
- std::string filename(get_lock_file_base_name());
+inline bool check_if_filename_complies_with_pid
+ (const char *filename, const char *prefix, OS_process_id_t pid, std::string &file_suffix, bool creation_time = false)
+{
+ //Check if filename complies with lock file name pattern
+ std::string fname(filename);
+ std::string fprefix(prefix);
+ if(fname.size() <= fprefix.size()){
+ return false;
+ }
+ fname.resize(fprefix.size());
+ if(fname != fprefix){
+ return false;
+ }
+
+ //If not our lock file, delete it if we can lock it
+ fname = filename;
+ fname.erase(0, fprefix.size());
pid_str_t pid_str;
- get_pid_str(pid_str);
- filename += pid_str;
+ get_pid_str(pid_str, pid);
+ file_suffix = pid_str;
+ if(creation_time){
+ std::size_t p = fname.find('_');
+ if (p == std::string::npos){
+ return false;
+ }
+ std::string save_suffix(fname);
+ fname.erase(p);
+ fname.swap(file_suffix);
+ bool ret = (file_suffix == fname);
+ file_suffix.swap(save_suffix);
+ return ret;
+ }
+ else{
+ fname.swap(file_suffix);
+ return (file_suffix == fname);
+ }
+}
- tmp_folder(s);
- s += "/";
- s += get_lock_file_subdir_name();
- s += "/";
- s += filename;
+} //file_locking_helpers
+
+namespace intermodule_singleton_helpers {
+
+const int GMemMarkToBeRemoved = -1;
+const int GMemNotPresent = -2;
+
+inline const char *get_lock_file_subdir_name()
+{ return "gmem"; }
+
+inline const char *get_lock_file_base_name()
+{ return "lck"; }
+
+inline void create_and_get_singleton_lock_file_path(std::string &s)
+{
+ file_locking_helpers::create_tmp_subdir_and_get_pid_based_filepath
+ (get_lock_file_subdir_name(), get_lock_file_base_name(), get_current_process_id(), s, true);
}
inline const char *get_shm_base_name()
@@ -107,55 +147,26 @@
inline void get_shm_name(std::string &shm_name)
{
- shm_name = get_shm_base_name();
- pid_str_t pid_str;
- get_pid_str(pid_str);
- shm_name += pid_str;
+ file_locking_helpers::get_pid_creation_time_str(shm_name);
+ shm_name.insert(0, get_shm_base_name());
}
inline std::size_t get_shm_size()
{ return 65536; }
-inline bool is_other_process_gmem_lock_file(const char *filename, std::string &pid_string)
-{
- const char * const base_str = get_lock_file_base_name();
- const std::size_t base_str_len = std::strlen(base_str);
- const std::size_t filename_length = std::strlen(filename);
-
- //Get pid string
- pid_str_t pid_str;
- get_pid_str(pid_str);
-
- //Check filename length
- const std::size_t pid_str_len = std::strlen(pid_str);
- if(base_str_len >= filename_length){
- return false;
- }
- //Check base str
- for(std::size_t i = 0, max = base_str_len; i != max; ++i){
- if(base_str[i] != filename[i]){
- return false;
- }
- }
-
- pid_string = &filename[base_str_len];
- if((base_str_len + pid_str_len) != filename_length){
- return true;
- }
+inline void apply_gmem_erase_logic(const char *filepath, const char *filename);
- //Check pid
- for(std::size_t i = base_str_len, max = filename_length, pid_i = 0; i != max; ++i, ++pid_i){
- if(filename[i] != pid_str[pid_i]){
- return true;
- }
- }
- return false;
+inline bool remove_old_gmem()
+{
+ std::string refcstrRootDirectory;
+ tmp_folder(refcstrRootDirectory);
+ refcstrRootDirectory += "/";
+ refcstrRootDirectory += get_lock_file_subdir_name();
+ return for_each_file_in_dir(refcstrRootDirectory.c_str(), apply_gmem_erase_logic);
}
-inline void apply_gmem_erase_logic(const char *filepath, const char *filename);
-
#if (defined BOOST_INTERPROCESS_WINDOWS)
-
+/*
inline bool remove_old_gmem()
{
void * hFile; // Handle to directory
@@ -193,7 +204,7 @@
}
return true;
}
-
+*/
struct locking_file_serial_id
{
@@ -201,7 +212,11 @@
unsigned long dwVolumeSerialNumber;
unsigned long nFileIndexHigh;
unsigned long nFileIndexLow;
- volatile boost::uint32_t ref_count;
+ //This reference count counts the number of modules attached
+ //to the shared memory and lock file. This serves to unlink
+ //the locking file and shared memory when all modules are
+ //done with the global memory (shared memory)
+ volatile boost::uint32_t modules_attached_to_gmem_count;
};
inline bool lock_locking_file(int fd)
@@ -220,8 +235,10 @@
inline int open_or_create_and_lock_file(const char *name)
{
+ permissions p;
+ p.set_unrestricted();
while(1){
- file_handle_t handle = create_or_open_file(name);
+ file_handle_t handle = create_or_open_file(name, read_write, p);
int fd = _open_osfhandle((intptr_t)handle, _O_TEXT);
if(fd < 0){
close_file(handle);
@@ -243,7 +260,7 @@
inline int try_open_and_lock_file(const char *name)
{
- file_handle_t handle = open_existing_file(name);
+ file_handle_t handle = open_existing_file(name, read_write);
int fd = _open_osfhandle((intptr_t)handle, _O_TEXT);
if(fd < 0){
close_file(handle);
@@ -292,7 +309,7 @@
id.dwVolumeSerialNumber = info.dwVolumeSerialNumber;
id.nFileIndexHigh = info.nFileIndexHigh;
id.nFileIndexLow = info.nFileIndexLow;
- id.ref_count = 1; //Initialize attached count
+ id.modules_attached_to_gmem_count = 1; //Initialize attached count
return true;
}
@@ -308,7 +325,7 @@
}
#else //UNIX
-
+/*
inline bool remove_old_gmem()
{
std::string refcstrRootDirectory;
@@ -341,7 +358,7 @@
fn += '/';
fn += de->d_name;
- if(std::remove(fn.c_str())) {
+ //if(std::remove(fn.c_str())) {
if(::stat(fn.c_str(), & st)) {
return false;
}
@@ -349,17 +366,21 @@
if(!S_ISDIR(st.st_mode)) {
apply_gmem_erase_logic(fn.c_str(), de->d_name);
}
- }
+ //}
}
return true;
}
-
+*/
struct locking_file_serial_id
{
int fd;
dev_t st_dev;
ino_t st_ino;
- volatile boost::uint32_t ref_count;
+ //This reference count counts the number of modules attached
+ //to the shared memory and lock file. This serves to unlink
+ //the locking file and shared memory when all modules are
+ //done with the global memory (shared memory)
+ volatile boost::uint32_t modules_attached_to_gmem_count;
};
inline bool lock_locking_file(int fd)
@@ -388,8 +409,10 @@
inline int open_or_create_and_lock_file(const char *name)
{
+ permissions p;
+ p.set_unrestricted();
while(1){
- int fd = create_or_open_file(name);
+ int fd = create_or_open_file(name, read_write, p);
if(fd < 0){
return fd;
}
@@ -409,7 +432,7 @@
inline int try_open_and_lock_file(const char *name)
{
- int fd = open_existing_file(name);
+ int fd = open_existing_file(name, read_write);
if(fd < 0){
return fd;
}
@@ -453,7 +476,7 @@
id.fd = fd;
id.st_dev = s.st_dev;
id.st_ino = s.st_ino;
- id.ref_count = 1; //Initialize attached count
+ id.modules_attached_to_gmem_count = 1; //Initialize attached count
return true;
}
@@ -471,8 +494,8 @@
struct gmem_erase_func
{
- gmem_erase_func(const char *shm_name, const char *lock_file_path, managed_shared_memory & shm)
- :shm_name_(shm_name), lock_file_path_(lock_file_path), shm_(shm)
+ gmem_erase_func(const char *shm_name, const char *singleton_lock_file_path, managed_shared_memory & shm)
+ :shm_name_(shm_name), singleton_lock_file_path_(singleton_lock_file_path), shm_(shm)
{}
void operator()()
@@ -481,27 +504,33 @@
if(pserial_id){
pserial_id->fd = GMemMarkToBeRemoved;
}
- delete_file(lock_file_path_);
+ delete_file(singleton_lock_file_path_);
shared_memory_object::remove(shm_name_);
}
const char * const shm_name_;
- const char * const lock_file_path_;
+ const char * const singleton_lock_file_path_;
managed_shared_memory & shm_;
};
+//This function applies shared memory erasure logic based on the passed lock file.
inline void apply_gmem_erase_logic(const char *filepath, const char *filename)
{
int fd = GMemMarkToBeRemoved;
try{
std::string str;
- if(!is_other_process_gmem_lock_file(filename, str)){
+ //If the filename is current process lock file, then avoid it
+ if(file_locking_helpers::check_if_filename_complies_with_pid
+ (filename, get_lock_file_base_name(), get_current_process_id(), str, true)){
return;
}
+ //Open and lock the other process' lock file
fd = try_open_and_lock_file(filepath);
if(fd < 0){
return;
}
+ //If done, then the process is dead so take global shared memory name
+ //(the name is based on the lock file name) and try to apply erasure logic
str.insert(0, get_shm_base_name());
try{
managed_shared_memory shm(open_only, str.c_str());
@@ -509,6 +538,7 @@
shm.try_atomic_func(func);
}
catch(interprocess_exception &e){
+ //If shared memory is not found erase the lock file
if(e.get_error_code() == not_found_error){
delete_file(filepath);
}
@@ -528,6 +558,7 @@
namespace intermodule_singleton_helpers {
+//The lock file logic creates uses a unique instance to a file
struct lock_file_logic
{
lock_file_logic(managed_shared_memory &shm)
@@ -544,19 +575,30 @@
void operator()(void)
{
retry_with_new_shm = false;
- locking_file_serial_id *pserial_id = mshm.find<locking_file_serial_id>("lock_file_fd").first;
+
+ //First find the file locking descriptor id
+ locking_file_serial_id *pserial_id =
+ mshm.find<locking_file_serial_id>("lock_file_fd").first;
int fd;
+ //If not found schedule a creation
if(!pserial_id){
fd = GMemNotPresent;
}
+ //Else get it
else{
fd = pserial_id->fd;
}
+ //If we need to create a new one, do it
if(fd == GMemNotPresent){
std::string lck_str;
- create_and_get_lock_file_path(lck_str);
+ //Create a unique current pid based lock file path
+ create_and_get_singleton_lock_file_path(lck_str);
+ //Open or create and lock file
int fd = intermodule_singleton_helpers::open_or_create_and_lock_file(lck_str.c_str());
+ //If failed, write a bad file descriptor to notify other modules that
+ //something was wrong and unlink shared memory. Mark the function object
+ //to tell caller to retry with another shared memory
if(fd < 0){
this->register_lock_file(GMemMarkToBeRemoved);
std::string s;
@@ -564,13 +606,21 @@
shared_memory_object::remove(s.c_str());
retry_with_new_shm = true;
}
+ //If successful, register the file descriptor
else{
this->register_lock_file(fd);
}
}
+ //If the fd was invalid (maybe a previous try failed) notify caller that
+ //should retry creation logic, since this shm might have been already
+ //unlinked since the shm was removed
else if (fd == GMemMarkToBeRemoved){
retry_with_new_shm = true;
}
+ //If the stored fd is not valid (a open fd, a normal file with the
+ //expected size, or does not have the same file id number,
+ //then it's an old shm from an old process with the same pid.
+ //If that's the case, mark it as invalid
else if(!is_valid_fd(fd) ||
!is_normal_file(fd) ||
0 != get_size(fd) ||
@@ -582,8 +632,9 @@
retry_with_new_shm = true;
}
else{
- //Valid lock file, just increment ref count
- atomic_inc32(&pserial_id->ref_count);
+ //If the lock file is ok, increment reference count of
+ //attached modules to shared memory
+ atomic_inc32(&pserial_id->modules_attached_to_gmem_count);
}
}
@@ -601,19 +652,30 @@
class intermodule_singleton_common
{
public:
- typedef void*(init_func_t)(managed_shared_memory &);
- typedef void (fini_func_t)(void *, managed_shared_memory &);
+ typedef void*(singleton_constructor_t)(managed_shared_memory &);
+ typedef void (singleton_destructor_t)(void *, managed_shared_memory &);
+
+ static const ::boost::uint32_t Uninitialized = 0u;
+ static const ::boost::uint32_t Initializing = 1u;
+ static const ::boost::uint32_t Initialized = 2u;
+ static const ::boost::uint32_t Broken = 3u;
- static void destroy_pc(void *ptr, fini_func_t fini_func)
+ static void finalize_singleton_logic(void *ptr, singleton_destructor_t destructor)
{
if(ptr)
- fini_func(ptr, get_shm());
- if(1 == atomic_dec32(&shm_ref_count)){
+ destructor(ptr, get_shm());
+ //If this is the last singleton of this module
+ //apply shm destruction.
+ //Note: singletons are destroyed when the module is unloaded
+ //so no threads should be executing or holding references
+ //to this module
+ if(1 == atomic_dec32(&this_module_singleton_count)){
destroy_shm();
}
}
- static void initialize_pc(void *&ptr, volatile boost::uint32_t &barrier, init_func_t ini_func);
+ static void initialize_singleton_logic
+ (void *&ptr, volatile boost::uint32_t &this_module_singleton_initialized, singleton_constructor_t ini_func);
private:
static managed_shared_memory &get_shm()
@@ -625,19 +687,21 @@
static void initialize_shm();
static void destroy_shm();
//Static data, zero-initalized without any dependencies
- static volatile boost::uint32_t shm_ref_count;
- static volatile boost::uint32_t shm_initialized;
+ //this_module_singleton_count is the number of singletons used by this module
+ static volatile boost::uint32_t this_module_singleton_count;
+ //this_module_shm_initialized is the state of this module's shm class object
+ static volatile boost::uint32_t this_module_shm_initialized;
static max_align shm_mem[MemSize];
};
template<int Dummy>
-volatile boost::uint32_t intermodule_singleton_common<Dummy>::shm_ref_count;
+volatile boost::uint32_t intermodule_singleton_common<Dummy>::this_module_singleton_count;
-template<int Dummy>
-const std::size_t intermodule_singleton_common<Dummy>::MemSize;
+//template<int Dummy>
+//const std::size_t intermodule_singleton_common<Dummy>::MemSize;
template<int Dummy>
-volatile boost::uint32_t intermodule_singleton_common<Dummy>::shm_initialized;
+volatile boost::uint32_t intermodule_singleton_common<Dummy>::this_module_shm_initialized;
template<int Dummy>
max_align intermodule_singleton_common<Dummy>::shm_mem[intermodule_singleton_common<Dummy>::MemSize];
@@ -645,30 +709,41 @@
template<int Dummy>
void intermodule_singleton_common<Dummy>::initialize_shm()
{
+ //Obtain unique shm name and size
std::string s;
intermodule_singleton_helpers::get_shm_name(s);
const char *ShmName = s.c_str();
const std::size_t ShmSize = intermodule_singleton_helpers::get_shm_size();;
while(1){
- ::boost::uint32_t tmp = atomic_cas32(&shm_initialized, 1, 0);
- if(tmp >= 2u){
+ //Try to pass shm state to initializing
+ ::boost::uint32_t tmp = atomic_cas32(&this_module_shm_initialized, Initializing, Uninitialized);
+ if(tmp >= Initialized){
break;
}
- else if(tmp == 1u){
+ //If some other thread is doing the work wait
+ else if(tmp == Initializing){
thread_yield();
}
- else{ //(tmp == 0u)
+ else{ //(tmp == Uninitialized)
+ //If not initialized try it again?
try{
+ //Remove old shared memory from the system
intermodule_singleton_helpers::remove_old_gmem();
+ //in-place construction of the shared memory class
::new (&get_shm())managed_shared_memory(open_or_create, ShmName, ShmSize);
- intermodule_singleton_helpers::lock_file_logic f(get_shm());
+ //Use shared memory internal lock to initialize the lock file
+ //that will mark this gmem as "in use".
+ intermodule_singleton_helpers::lock_file_logic f(get_shm());
get_shm().atomic_func(f);
+ //If function failed (maybe a competing process has erased the shared
+ //memory between creation and file locking), retry with a new instance.
if(f.retry_with_new_shm){
get_shm().~managed_shared_memory();
- atomic_write32(&shm_initialized, 0);
+ atomic_write32(&this_module_shm_initialized, Uninitialized);
}
else{
- atomic_write32(&shm_initialized, 2);
+ //Locking succeeded, so this shared memory module-instance is ready
+ atomic_write32(&this_module_shm_initialized, Initialized);
break;
}
}
@@ -691,12 +766,12 @@
mshm_.find<intermodule_singleton_helpers::locking_file_serial_id>
("lock_file_fd").first;
assert(0 != pserial_id);
- if(1 == atomic_dec32(&pserial_id->ref_count)){
+ if(1 == atomic_dec32(&pserial_id->modules_attached_to_gmem_count)){
int fd = pserial_id->fd;
if(fd > 0){
pserial_id->fd = intermodule_singleton_helpers::GMemMarkToBeRemoved;
std::string s;
- intermodule_singleton_helpers::get_lock_file_path(s);
+ intermodule_singleton_helpers::create_and_get_singleton_lock_file_path(s);
delete_file(s.c_str());
intermodule_singleton_helpers::close_lock_file(fd);
intermodule_singleton_helpers::get_shm_name(s);
@@ -710,51 +785,80 @@
template<int Dummy>
void intermodule_singleton_common<Dummy>::destroy_shm()
{
- if(!atomic_read32(&shm_ref_count)){
+ if(!atomic_read32(&this_module_singleton_count)){
+ //This module is being unloaded, so destroy
+ //the shared memory object of this module
+ //and unlink the shared memory if it's the last
unlink_shmlogic f(get_shm());
get_shm().atomic_func(f);
(get_shm()).~managed_shared_memory();
- atomic_write32(&shm_initialized, 0u);
+ atomic_write32(&this_module_shm_initialized, Uninitialized);
+ //Do some cleanup for other processes old gmem instances
intermodule_singleton_helpers::remove_old_gmem();
}
}
+//Initialize this_module_singleton_ptr, creates the shared memory if needed and also creates an unique
+//opaque type in shared memory through a singleton_constructor_t function call,
+//initializing the passed pointer to that unique instance.
+//
+//We have two concurrency types here. a)the shared memory/singleton creation must
+//be safe between threads of this process but in different modules/dlls. b)
+//the pointer to the singleton is per-module, so we have to protect this
+//initization between threads of the same module.
+//
+//All static variables declared here are shared between inside a module
+//so atomic operations will synchronize only threads of the same module.
template<int Dummy>
-void intermodule_singleton_common<Dummy>::initialize_pc(void *&ptr, volatile boost::uint32_t &barrier, init_func_t init_func)
+void intermodule_singleton_common<Dummy>::initialize_singleton_logic
+ (void *&ptr, volatile boost::uint32_t &this_module_singleton_initialized, singleton_constructor_t constructor)
{
- // insert memory barrier
- if(atomic_read32(&barrier) != 2u){
- //Try to pass from 0 to 1, and insert memory barrier
- ::boost::uint32_t tmp_barrier = atomic_cas32(&barrier, 1, 0);
- if(tmp_barrier == 0u){
+ //If current module is not initialized enter to lock free logic
+ if(atomic_read32(&this_module_singleton_initialized) != Initialized){
+ //Now a single thread of the module will succeed in this CAS.
+ //trying to pass from Uninitialized to Initializing
+ ::boost::uint32_t previous_module_singleton_initialized = atomic_cas32
+ (&this_module_singleton_initialized, Initializing, Uninitialized);
+ //If the thread succeeded the CAS (winner) it will compete with other
+ //winner threads from other modules to create the shared memory
+ if(previous_module_singleton_initialized == Uninitialized){
try{
+ //Now initialize shm, this function solves concurrency issues
+ //between threads of several modules
initialize_shm();
- atomic_inc32(&shm_ref_count);
- //This can throw
- void *tmp = init_func(get_shm());
- //Barrier...
- atomic_write32(&barrier, 1u);
- //This won't throw
+ //Increment the module reference count that reflects how many
+ //singletons this module holds, so that we can safely destroy
+ //module shared memory object when no singleton is left
+ atomic_inc32(&this_module_singleton_count);
+ //Now try to create the singleton in shared memory.
+ //This function solves concurrency issues
+ //between threads of several modules
+ void *tmp = constructor(get_shm());
+ //Insert a barrier before assigning the pointer to
+ //make sure this assignment comes after the initialization
+ atomic_write32(&this_module_singleton_initialized, Initializing);
+ //Assign the singleton address to the module-local pointer
ptr = tmp;
//Memory barrier inserted, all previous operations should complete
- //before this one
- atomic_inc32(&barrier);
+ //before this one. Now marked as initialized
+ atomic_inc32(&this_module_singleton_initialized);
}
catch(...){
//Mark singleton failed to initialize
- atomic_write32(&barrier, 3u);
+ atomic_write32(&this_module_singleton_initialized, Broken);
throw;
}
}
- else if(tmp_barrier == 1u){
- //Another thread is initializing the singleton, just wait
+ //If previous state was initializing, this means that another winner thread is
+ //trying to initialize the singleton. Just wait until completes its work.
+ else if(previous_module_singleton_initialized == Initializing){
while(1){
- tmp_barrier = atomic_read32(&barrier);
- if(tmp_barrier >= 2u){
+ previous_module_singleton_initialized = atomic_read32(&this_module_singleton_initialized);
+ if(previous_module_singleton_initialized >= Initialized){
//Already initialized, or exception thrown by initializer thread
break;
}
- else if(tmp_barrier == 1u){
+ else if(previous_module_singleton_initialized == Initializing){
detail::thread_yield();
}
else{
@@ -763,65 +867,95 @@
}
}
}
- if(tmp_barrier > 2u){
- //Exception thrown, singleton initialization failed
- throw interprocess_exception();
+ else if(previous_module_singleton_initialized == Initialized){
+ //Nothing to do here, the singleton is ready
+ }
+ //If previous state was greater than initialized, then memory is broken
+ //trying to initialize the singleton.
+ else{//(previous_module_singleton_initialized > Initialized)
+ throw interprocess_exception("boost::interprocess::intermodule_singleton initialization failed");
}
}
assert(ptr != 0);
}
-
-//Now this class is a classic singleton, initializing the singleton in
-//the first get() function call
-
-template<typename C>
+//Now this class is a singleton, initializing the singleton in
+//the first get() function call if LazyInit is false. If true
+//then the singleton will be initialized when loading the module.
+template<typename C, bool LazyInit = false>
class intermodule_singleton
{
public:
static C& get() //Let's make inlining easy
{
- if(!pc){
- if(deleter.dummy_function()) //This forces deleter instantiation, for reference counted destruction
- intermodule_singleton_common<0>::initialize_pc(pc, barrier, initialize);
+ if(!this_module_singleton_ptr){
+ if(lifetime.dummy_function()) //This forces lifetime instantiation, for reference counted destruction
+ intermodule_singleton_common<0>::initialize_singleton_logic
+ (this_module_singleton_ptr, this_module_singleton_initialized, singleton_constructor);
}
- return *static_cast<C*>(pc);
+ return *static_cast<C*>(this_module_singleton_ptr);
}
struct ref_count_ptr
{
ref_count_ptr(C *p, boost::uint32_t count)
- : ptr(p), ref_count(count)
+ : ptr(p), singleton_ref_count(count)
{}
C *ptr;
- volatile boost::uint32_t ref_count;
+ //This reference count serves to count the number of attached
+ //modules to this singleton
+ volatile boost::uint32_t singleton_ref_count;
};
private:
- //These will be zero-initialized without any constructor call dependency
- static void* pc;
- static volatile boost::uint32_t barrier;
+ //These statics will be zero-initialized without any constructor call dependency
+ //this_module_singleton_ptr will be a module-local pointer to the singleton
+ static void* this_module_singleton_ptr;
+ //this_module_singleton_count will be used to synchronize threads of the same module
+ //for access to a singleton instance, and to flag the state of the
+ //singleton.
+ static volatile boost::uint32_t this_module_singleton_initialized;
+
//This class destructor will trigger singleton destruction
- static struct deleter_type
+ struct lifetime_type_lazy
{
bool dummy_function()
{ return m_dummy == 0; }
- ~deleter_type()
+ ~lifetime_type_lazy()
{
- intermodule_singleton_common<0>::destroy_pc(pc, finalize);
+ intermodule_singleton_common<0>::finalize_singleton_logic
+ (this_module_singleton_ptr, singleton_destructor);
}
//Dummy volatile so that the compiler can't resolve its value at compile-time
- //and can't avoid deleter_type instantiation if dummy_function() is called.
+ //and can't avoid lifetime_type instantiation if dummy_function() is called.
static volatile int m_dummy;
- } deleter;
+ };
-
+ struct lifetime_type_static
+ : public lifetime_type_lazy
+ {
+ lifetime_type_static()
+ {
+ intermodule_singleton_common<0>::initialize_singleton_logic
+ (this_module_singleton_ptr, this_module_singleton_initialized, singleton_constructor);
+ }
+ };
+
+ typedef typename if_c
+ <LazyInit, lifetime_type_lazy, lifetime_type_static>::type lifetime_type;
+
+ static lifetime_type lifetime;
+
+ //A functor to be executed inside shared memory lock that just
+ //searches for the singleton in shm and if not present creates a new one.
+ //If singleton constructor throws, the exception is propagated
struct init_atomic_func
{
init_atomic_func(managed_shared_memory &m)
: mshm(m)
{}
+
void operator()()
{
ref_count_ptr *rcount = mshm.find<ref_count_ptr>(unique_instance).first;
@@ -835,25 +969,28 @@
throw;
}
}
- atomic_inc32(&rcount->ref_count);
+ atomic_inc32(&rcount->singleton_ref_count);
ret_ptr = rcount->ptr;
}
managed_shared_memory &mshm;
void *ret_ptr;
};
+ //A functor to be executed inside shared memory lock that just
+ //deletes the singleton in shm if the attached count reaches to zero
struct fini_atomic_func
{
fini_atomic_func(managed_shared_memory &m)
: mshm(m)
{}
+
void operator()()
{
ref_count_ptr *rcount = mshm.find<ref_count_ptr>(unique_instance).first;
//The object must exist
assert(rcount);
//Check if last reference
- if(atomic_dec32(&rcount->ref_count) == 1){
+ if(atomic_dec32(&rcount->singleton_ref_count) == 1){
//If last, destroy the object
assert(rcount->ptr != 0);
delete rcount->ptr;
@@ -866,33 +1003,34 @@
void *ret_ptr;
};
-
- static void *initialize(managed_shared_memory &mshm)
+ //A wrapper to execute init_atomic_func
+ static void *singleton_constructor(managed_shared_memory &mshm)
{
init_atomic_func f(mshm);
mshm.atomic_func(f);
return f.ret_ptr;
}
- static void finalize(void *p, managed_shared_memory &mshm)
+ //A wrapper to execute fini_atomic_func
+ static void singleton_destructor(void *p, managed_shared_memory &mshm)
{ (void)p;
fini_atomic_func f(mshm);
mshm.atomic_func(f);
}
};
-template <typename C>
-volatile int intermodule_singleton<C>::deleter_type::m_dummy;
+template <typename C, bool L>
+volatile int intermodule_singleton<C, L>::lifetime_type_lazy::m_dummy;
//These will be zero-initialized by the loader
-template <typename C>
-void *intermodule_singleton<C>::pc;
+template <typename C, bool L>
+void *intermodule_singleton<C, L>::this_module_singleton_ptr;
-template <typename C>
-volatile boost::uint32_t intermodule_singleton<C>::barrier;
+template <typename C, bool L>
+volatile boost::uint32_t intermodule_singleton<C, L>::this_module_singleton_initialized;
-template <typename C>
-typename intermodule_singleton<C>::deleter_type intermodule_singleton<C>::deleter;
+template <typename C, bool L>
+typename intermodule_singleton<C, L>::lifetime_type intermodule_singleton<C, L>::lifetime;
} //namespace detail{