User:Kr/A Thread's Life/Library Example with SAL

From Apache OpenOffice Wiki
Jump to: navigation, search

SAL Thread Issues:

  • Different semantic of UNIX and Win32 implementations
  • Problematic "pthread_detach" in UNIX usage, likely leading to races if trying to join a thread.
  • Problematic "CloseHandle" in Win32 usage, only easily possible to create "detached" (daemon) threads if calling "osl_destroyThread" from within the new thread.

RFE:

  • Reliable thread cancellation mechanism ...
  • Result setting function. Needed in multi-thread keeping process alive scenario.
  • Passing of the "oslThread" object to the worker function, otherwise it must be explicitly passed with help of conditions etc.
  • Better named "osl_scheduleThread".
  • A way to get this threads "oslThread".
  • Missing pendant to "pthread_exit" / "ExitThread" and therefore also missing clean-up handlers etc.
  • Less capable cancellation mechanism compared to "pthread_cancel"

How-to Build

Get an OOo build environment
mkdir salexample
mkdir salexample/source
mkdir salexample/prj
touch salexample/prj/d.lst
cd salexample/source
dmake

The Program

#include "library.hxx"
 
#include <sal/main.h>
#include <osl/interlck.h>
#include <osl/thread.h>
#include <osl/module.hxx>
#include <rtl/alloc.h>
 
#include <stdio.h>
#include <time.h>
 
#ifdef WNT
extern "C" void _endthread(void);
 
#else
# include <pthread.h>
 
#endif
 
 
static oslInterlockedCount activities_ = 1; /* The "main" thread is the first "activity". */
 
static void activity_terminate_(void) {
    int use_exit = 0;
 
    use_exit = osl_decrementInterlockedCount(&activities_) == 0;
 
    /* Terminate the process, if this was the last "activity"! */
    if (use_exit)
        exit(0);
 
    else
#ifdef WNT
        _endthread();
#else
        pthread_exit(NULL);
#endif
}
 
typedef void activity_worker_t(void);
 
static void activity_func_(activity_worker_t ** ffunc) {
    activity_worker_t * func = *ffunc;
    rtl_freeMemory(ffunc);
 
    func();
 
    activity_terminate_();
}
 
static void activity_create_(activity_worker_t * func) {
    activity_worker_t ** ffunc = (activity_worker_t **)rtl_allocateMemory(sizeof(activity_worker_t *));
    *ffunc = func;
    oslThread thread = osl_createThread((oslWorkerFunction)activity_func_, ffunc);
 
    /* Activities need to be detached. */
#ifndef UNX
    TimeValue oneSecond_ = {1, 0};
    osl_waitThread(&oneSecond_); 
 
    osl_destroyThread(thread);
 
#else
    (void)thread;
 
#endif
 
    osl_incrementInterlockedCount(&activities_);
}
 
 
/* Some daemon functions. */
static daemon_create_t    * pdaemon_create_;
static daemons_getCount_t * pdaemons_getCount_;
 
 
extern "C" void log_threads(void) {
    fprintf(stderr, "activities: %u  daemons: %u\n", activities_, pdaemons_getCount_ ? pdaemons_getCount_() : 0);
}
 
static TimeValue oneSecond_ = {1, 0};
 
static void log_daemon_(oslThread thread) {
    fprintf(stderr, "\tlog daemon starting ...\n");
 
    while (osl_scheduleThread(thread)) {
        log_threads();
 
        osl_waitThread(&oneSecond_); 
    }
 
    fprintf(stderr, "\tlog daemon finishing ...\n");
}
 
static void some_daemon_(oslThread thread) /*throw (int)*/ {
    fprintf(stderr, "\tsome daemon starting ...\n");
 
    int n = 10;
    while (osl_scheduleThread(thread) && n > 0) {
        osl_waitThread(&oneSecond_); 
 
        if (rand() < (RAND_MAX / (pdaemons_getCount_() + 1)))
            pdaemon_create_(some_daemon_, thread);
 
        -- n;
    }
    fprintf(stderr, "\tsome daemon finishing ...\n");
}
 
/* Some activity functions. */
static void some_activity_(void) {
    fprintf(stderr, "\tsome activitiy starting ...\n");
 
    srand(time (0));
 
    int n = 3;
    while (n) {
        osl_waitThread(&oneSecond_); 
 
        if (rand() < (RAND_MAX / (activities_ + 1)))
            activity_create_(some_activity_);
 
        if (rand() < (RAND_MAX / (pdaemons_getCount_() + 1)))
            pdaemon_create_(some_daemon_, NULL);
 
        -- n;
    }
 
    fprintf(stderr, "\tsome activitiy dying ...\n");
}
 
static osl::Module library;
 
#if defined GCC
# define DAEMON_CREATE          "_Z13daemon_createPFvPvES_"
# define DAEMONS_GETCOUNT       "_Z16daemons_getCountv"
# define DAEMONS_CANCELANDJOIN  "_Z21daemons_cancelAndJoinv"
 
#elif defined __SUNPRO_CC
# define DAEMON_CREATE          "__1cNdaemon_create6FpFpv_v0_v_"
# define DAEMONS_GETCOUNT       "__1cQdaemons_getCount6F_i_"
# define DAEMONS_CANCELANDJOIN  "__1cVdaemons_cancelAndJoin6F_v_"
 
#elif defined _MSC_VER
# define DAEMON_CREATE          "?daemon_create@@YAXP6AXPAX@Z0@Z"
# define DAEMONS_GETCOUNT       "?daemons_getCount@@YAHXZ"
# define DAEMONS_CANCELANDJOIN  "?daemons_cancelAndJoin@@YAXXZ"
 
#else
# error "unknown compiler"
 
#endif
 
extern "C" void close_library(void) {
    daemons_cancelAndJoin_t * pdaemons_cancelAndJoin = 
         (daemons_cancelAndJoin_t *)library.getFunctionSymbol(rtl::OUString(RTL_CONSTASCII_USTRINGPARAM(DAEMONS_CANCELANDJOIN)));
    pdaemons_cancelAndJoin();
    library.unload();
    pdaemon_create_ = NULL;
    pdaemons_getCount_ = NULL;
}
 
SAL_IMPLEMENT_MAIN()
{
    atexit(log_threads);
    atexit(close_library);
 
    library.load(rtl::OUString(RTL_CONSTASCII_USTRINGPARAM("library" SAL_DLLEXTENSION)));
    pdaemon_create_    = (daemon_create_t *)library.getFunctionSymbol(
        rtl::OUString(RTL_CONSTASCII_USTRINGPARAM(DAEMON_CREATE)));
    pdaemons_getCount_ = (daemons_getCount_t *)library.getFunctionSymbol(
        rtl::OUString(RTL_CONSTASCII_USTRINGPARAM(DAEMONS_GETCOUNT)));
 
    pdaemon_create_(log_daemon_, NULL);
 
    some_activity_();
 
    activity_terminate_();
 
    return 0;
}

Library Header

[cpp]
#ifndef library_hxx_included
#  define library_hxx_included
 
#include <osl/thread.h>
 
#ifdef LIBRARY_IMPL
# define LIBRARY_EXPORT SAL_DLLPUBLIC_EXPORT
 
#else
# define LIBRARY_EXPORT SAL_DLLPUBLIC_IMPORT
 
#endif
 
 
typedef void daemon_worker_t(oslThread thread);
 
typedef void daemon_create_t        (daemon_worker_t * func, oslThread thread);
typedef int  daemons_getCount_t     (void);
typedef void daemons_cancelAndJoin_t(void);
 
LIBRARY_EXPORT void daemon_create        (daemon_worker_t * func, oslThread thread) /*throw (int)*/;
LIBRARY_EXPORT int  daemons_getCount     (void);
LIBRARY_EXPORT void daemons_cancelAndJoin(void);
 
 
#endif

Library Implementation

[cpp]
#define LIBRARY_IMPL
 
#include "library.hxx"
 
#include <rtl/alloc.h>
#include <osl/mutex.h>
#include <osl/thread.h>
 
#include <stdio.h>
 
 
typedef struct Daemon  Daemon;
 
struct Daemon {
    Daemon * previous_;
    Daemon * next_;
 
    daemon_worker_t * func_;
    oslThread         hd_;
    int               finished_;
};
 
static oslMutex daemons_mutex_;
struct DaemonConstruct {
    DaemonConstruct() {
        daemons_mutex_ = osl_createMutex();
    }
 
    ~DaemonConstruct() {
        osl_destroyMutex(daemons_mutex_);
    }        
};
 
static DaemonConstruct daemonConstruct;
 
static Daemon     * firstDaemon_ = NULL;
static unsigned int daemons_     = 0; 
 
int daemons_getCount(void) {
    return daemons_;
}
 
/* Joins all or only "finished" daemons. */
static void daemons_join_(int finished) {
    osl_acquireMutex(daemons_mutex_);
    Daemon * daemon = firstDaemon_;
    while (daemon) {
        Daemon * next = daemon->next_;
 
        if (!finished || daemon->finished_) {
            -- daemons_;
 
            if (daemon->next_)
                daemon->next_->previous_ = daemon->previous_;
 
            if (daemon->previous_)
                daemon->previous_->next_ = daemon->next_;
 
            if (firstDaemon_ == daemon)
                firstDaemon_ = daemon->next_;
 
            osl_releaseMutex(daemons_mutex_);
            osl_joinWithThread(daemon->hd_);
            osl_acquireMutex(daemons_mutex_);
 
            osl_destroyThread(daemon->hd_);
 
            rtl_freeMemory(daemon);
 
            daemon = firstDaemon_;
        }
        else
            daemon = next;
    }
    osl_releaseMutex(daemons_mutex_);
}
 
/* Daemon finish function. */
static void daemon_finish_(Daemon * daemon) {
    daemons_join_(1);
 
    osl_acquireMutex(daemons_mutex_);
    daemon->finished_ = 1;
    osl_releaseMutex(daemons_mutex_);
}
 
static void daemon_func_(Daemon * daemon) {
    try {
        daemon->func_(daemon->hd_);
    }
    catch (...) {
        fprintf(stderr, " caught something ...\n");
    }
 
    daemon_finish_(daemon);
}
 
/* Create a "Daemon" struct and register it. Start the "Daemon". */
LIBRARY_EXPORT void daemon_create(daemon_worker_t * func, oslThread thread) /*throw (int)*/ {
    Daemon * daemon   = (Daemon *)rtl_allocateMemory(sizeof(Daemon));
    daemon->func_     = func;
    daemon->finished_ = 0;
 
    osl_acquireMutex(daemons_mutex_);
    // add a cancelation point
    if (thread && !osl_scheduleThread(thread)) {
        osl_releaseMutex(daemons_mutex_);
        rtl_freeMemory(daemon);
        throw int();
    }
 
    daemon->previous_ = NULL;
    daemon->next_ = firstDaemon_;
 
    if (firstDaemon_) 
        firstDaemon_->previous_ = daemon;
 
    firstDaemon_ = daemon;
    ++ daemons_;
 
    daemon->hd_ = osl_createSuspendedThread((oslWorkerFunction)daemon_func_, daemon);
    osl_resumeThread(daemon->hd_);
 
    osl_releaseMutex(daemons_mutex_);
}
 
/* Ask all registered daemons for cancellation and join them. */
/* Calling pthread_canel from within _fini leads to deadlocks.*/
/* static void __attribute__((destructor)) daemons_cancelAndJoin_(void) {*/
 
void daemons_cancelAndJoin(void) {
    fprintf(stderr, "Cancelling daemons ... ");
 
    osl_acquireMutex(daemons_mutex_);
    Daemon * daemon = firstDaemon_;
    while (daemon) {
        osl_terminateThread(daemon->hd_);
        /* respectively "osl_killThread" :-) */
 
        fprintf(stderr, "# ");
 
        daemon = daemon->next_;
    }
    osl_releaseMutex(daemons_mutex_);
    fprintf(stderr, "done\n");
 
 
    fprintf(stderr, "Joining daemons ... ");
    daemons_join_(0);
    fprintf(stderr, "done\n");
}
 
struct LibExit {
    LibExit() {
        fprintf(stderr, "initializing library ...\n");
    }
 
    ~LibExit() {
        fprintf(stderr, "de-initializing library ...\n");
//        daemons_cancelAndJoin();
    }
};
 
static LibExit libExit;

Makefile

PRJ     := ..
PRJNAME := SALTHREADS
TARGET  := main
USE_DEFFILE        := TRUE
 
ENABLE_EXCEPTIONS  := TRUE
 
.INCLUDE :  settings.mk
 
 
.IF "$(OS)"=="SOLARIS"
DIRECT :=
.ENDIF
 
APP1TARGET  := main
APP1OBJS    := $(OBJ)$/main.obj
.IF "$(OS)"=="SOLARIS"
APP1STDLIBS := -lrary $(SALLIB) 
.ELSE
APP1STDLIBS := $(SALLIB) 
.ENDIF
 
SHL1DLLPRE  := 
SHL1TARGET  := library
SHL1OBJS    := $(SLO)$/library.obj
SHL1STDLIBS := $(SALHELPERLIB) $(SALLIB)
#SHL1IMPLIB  := i$(SHL1TARGET)
SHL1DEF     := empty.def
 
 
.INCLUDE :  target.mk

The DEF File

HEAPSIZE	  0
EXPORTS
Personal tools