threads.c

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// Thread handling stuff for the Citadel server
//
// Copyright (c) 1987-2023 by the citadel.org team
//
// This program is open source software.  Use, duplication, or disclosure
// is subject to the terms of the GNU General Public License, version 3.
 
#include <errno.h>
#include <stdio.h>
#include <syslog.h>
#include <libcitadel.h>
#include "modules_init.h"
#include "serv_extensions.h"
#include "ctdl_module.h"
#include "config.h"
#include "context.h"
#include "threads.h"
 
int num_workers = 0;                // Current number of worker threads
int active_workers = 0;             // Number of ACTIVE worker threads
pthread_mutex_t Critters[MAX_SEMAPHORES];   // Things needing locking
int server_shutting_down = 0;           // set to nonzero during shutdown
pthread_mutex_t ThreadCountMutex;
 
void InitializeSemaphores(void) {
    int i;
 
    // Set up a bunch of semaphores to be used for critical sections
    for (i=0; i<MAX_SEMAPHORES; ++i) {
        pthread_mutex_init(&Critters[i], NULL);
    }
}
 
 
// Obtain a semaphore lock to begin a critical section, but only if no one else has one
//int try_critical_section(int which_one) {
    // For all types of critical sections except those listed here,
    // ensure nobody ever tries to do a critical section within a
    // transaction; this could lead to deadlock.
    //if (  (which_one != S_FLOORCACHE)
        //&& (which_one != S_NETCONFIGS)
    //) {
        //cdb_check_handles();
    //}
    //return (pthread_mutex_trylock(&Critters[which_one]));
//}
 
 
// Obtain a semaphore lock to begin a critical section.
void begin_critical_section(int which_one) {
    // For all types of critical sections except those listed here,
    // ensure nobody ever tries to do a critical section within a
    // transaction; this could lead to deadlock.
    if ((which_one != S_FLOORCACHE) && (which_one != S_NETCONFIGS)) {
        cdb_check_handles();
    }
 
    pthread_mutex_lock(&Critters[which_one]);
}
 
 
// Release a semaphore lock to end a critical section.
void end_critical_section(int which_one) {
    pthread_mutex_unlock(&Critters[which_one]);
}
 
 
// Function to create a thread.
void CtdlThreadCreate(void *(*start_routine)(void*)) {
    pthread_t thread;
    pthread_attr_t attr;
    int ret = 0;
 
    ret = pthread_attr_init(&attr);
    ret = pthread_attr_setstacksize(&attr, THREADSTACKSIZE);
    ret = pthread_create(&thread, &attr, start_routine, NULL);
    if (ret != 0) syslog(LOG_ERR, "pthread_create() : %m");
}
 
 
// Initialize the thread system
void go_threading(void) {
    pthread_mutex_init(&ThreadCountMutex, NULL);
 
    // Second call to module init functions now that threading is up
    initialize_modules(1);
 
    // Begin with one worker thread.  We will expand the pool if necessary
    CtdlThreadCreate(worker_thread);
 
    // The supervisor thread monitors worker threads and spawns more of them if it finds that they are all in use.
    while (!server_shutting_down) {
        if ((active_workers == num_workers) && (num_workers < CtdlGetConfigInt("c_max_workers"))) {
            CtdlThreadCreate(worker_thread);
        }
        usleep(1000000);
    }
 
    // When we get to this point we are getting ready to shut down our Citadel server
    terminate_all_sessions();       // close all client sockets
    CtdlShutdownServiceHooks();     // close all listener sockets to prevent new connections
    PerformSessionHooks(EVT_SHUTDOWN);  // run any registered shutdown hooks
 
    // We used to wait for all threads to exit.  Fuck that.  The only thing important is that the databases are
    // cleanly unmounted.  After that, exit the whole program.
}