citadel/threads.c

   1 /*
   2  * Thread handling stuff for Citadel server
   3  *
   4  * Copyright (c) 1987-2011 by the citadel.org team
   5  *
   6  * This program is open source software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  */
  20
  21 #include <stdlib.h>
  22 #include <unistd.h>
  23 #include <stdio.h>
  24 #include <sys/types.h>
  25 #include <errno.h>
  26 #include <sys/socket.h>
  27 #include <unistd.h>
  28 #include <fcntl.h>
  29 #include <signal.h>
  30 #include <syslog.h>
  31
  32 #include "sysdep.h"
  33 #if TIME_WITH_SYS_TIME
  34 # include <sys/time.h>
  35 # include <time.h>
  36 #else
  37 # if HAVE_SYS_TIME_H
  38 #  include <sys/time.h>
  39 # else
  40 #  include <time.h>
  41 # endif
  42 #endif
  43
  44 #ifdef HAVE_SYSCALL_H
  45 # include <syscall.h>
  46 #else
  47 # if HAVE_SYS_SYSCALL_H
  48 #  include <sys/syscall.h>
  49 # endif
  50 #endif
  51
  52 #include <libcitadel.h>
  53
  54 #include "threads.h"
  55 #include "ctdl_module.h"
  56 #include "modules_init.h"
  57 #include "housekeeping.h"
  58 #include "config.h"
  59 #include "citserver.h"
  60 #include "sysdep_decls.h"
  61 #include "context.h"
  62 #include "event_client.h"
  63
  64 /*
  65  * define this to use the new worker_thread method of handling connections
  66  */
  67 //#define NEW_WORKER
  68
  69 /*
  70  * New thread interface.
  71  * To create a thread you must call one of the create thread functions.
  72  * You must pass it the address of (a pointer to a CtdlThreadNode initialised to NULL) like this
  73  * struct CtdlThreadNode *node = NULL;
  74  * pass in &node
  75  * If the thread is created *node will point to the thread control structure for the created thread.
  76  * If the thread creation fails *node remains NULL
  77  * Do not free the memory pointed to by *node, it doesn't belong to you.
  78  * This new interface duplicates much of the eCrash stuff. We should go for closer integration since that would
  79  * remove the need for the calls to eCrashRegisterThread and friends
  80  */
  81
  82 static int num_threads = 0;                     /* Current number of threads */
  83 static int num_workers = 0;                     /* Current number of worker threads */
  84
  85 CtdlThreadNode *CtdlThreadList = NULL;
  86 CtdlThreadNode *CtdlThreadSchedList = NULL;
  87
  88 static CtdlThreadNode *GC_thread = NULL;
  89 static char *CtdlThreadStates[CTDL_THREAD_LAST_STATE];
  90 double CtdlThreadLoadAvg = 0;
  91 double CtdlThreadWorkerAvg = 0;
  92 citthread_key_t ThreadKey;
  93
  94 citthread_mutex_t Critters[MAX_SEMAPHORES];     /* Things needing locking */
  95
  96
  97
  98 void InitialiseSemaphores(void)
  99 {
 100         int i;
 101
 102         /* Set up a bunch of semaphores to be used for critical sections */
 103         for (i=0; i<MAX_SEMAPHORES; ++i) {
 104                 citthread_mutex_init(&Critters[i], NULL);
 105         }
 106 }
 107
 108
 109
 110
 111 /*
 112  * Obtain a semaphore lock to begin a critical section.
 113  * but only if no one else has one
 114  */
 115 int try_critical_section(int which_one)
 116 {
 117         /* For all types of critical sections except those listed here,
 118          * ensure nobody ever tries to do a critical section within a
 119          * transaction; this could lead to deadlock.
 120          */
 121         if (    (which_one != S_FLOORCACHE)
 122 #ifdef DEBUG_MEMORY_LEAKS
 123                 && (which_one != S_DEBUGMEMLEAKS)
 124 #endif
 125                 && (which_one != S_RPLIST)
 126         ) {
 127                 cdb_check_handles();
 128         }
 129         return (citthread_mutex_trylock(&Critters[which_one]));
 130 }
 131
 132
 133 /*
 134  * Obtain a semaphore lock to begin a critical section.
 135  */
 136 void begin_critical_section(int which_one)
 137 {
 138         /* syslog(LOG_DEBUG, "begin_critical_section(%d)\n", which_one); */
 139
 140         /* For all types of critical sections except those listed here,
 141          * ensure nobody ever tries to do a critical section within a
 142          * transaction; this could lead to deadlock.
 143          */
 144         if (    (which_one != S_FLOORCACHE)
 145 #ifdef DEBUG_MEMORY_LEAKS
 146                 && (which_one != S_DEBUGMEMLEAKS)
 147 #endif
 148                 && (which_one != S_RPLIST)
 149         ) {
 150                 cdb_check_handles();
 151         }
 152         citthread_mutex_lock(&Critters[which_one]);
 153 }
 154
 155 /*
 156  * Release a semaphore lock to end a critical section.
 157  */
 158 void end_critical_section(int which_one)
 159 {
 160         citthread_mutex_unlock(&Critters[which_one]);
 161 }
 162
 163
 164 /*
 165  * A function to destroy the TSD
 166  */
 167 static void ctdl_thread_internal_dest_tsd(void *arg)
 168 {
 169         if (arg != NULL) {
 170                 check_handles(arg);
 171                 free(arg);
 172         }
 173 }
 174
 175
 176 /*
 177  * A function to initialise the thread TSD
 178  */
 179 void ctdl_thread_internal_init_tsd(void)
 180 {
 181         int ret;
 182
 183         if ((ret = citthread_key_create(&ThreadKey, ctdl_thread_internal_dest_tsd))) {
 184                 syslog(LOG_EMERG, "citthread_key_create: %s\n", strerror(ret));
 185                 exit(CTDLEXIT_DB);
 186         }
 187 }
 188
 189 /*
 190  * Ensure that we have a key for thread-specific data.
 191  *
 192  * This should be called immediately after startup by any thread
 193  *
 194  */
 195 void CtdlThreadAllocTSD(void)
 196 {
 197         ThreadTSD *tsd;
 198
 199         if (citthread_getspecific(ThreadKey) != NULL)
 200                 return;
 201
 202         tsd = malloc(sizeof(ThreadTSD));
 203
 204         tsd->tid = NULL;
 205
 206         memset(tsd->cursors, 0, sizeof tsd->cursors);
 207         tsd->self = NULL;
 208
 209         citthread_setspecific(ThreadKey, tsd);
 210 }
 211
 212
 213 void ctdl_thread_internal_free_tsd(void)
 214 {
 215         ctdl_thread_internal_dest_tsd(citthread_getspecific(ThreadKey));
 216         citthread_setspecific(ThreadKey, NULL);
 217 }
 218
 219
 220 void ctdl_thread_internal_cleanup(void)
 221 {
 222         int i;
 223         CtdlThreadNode *this_thread, *that_thread;
 224
 225         for (i=0; i<CTDL_THREAD_LAST_STATE; i++)
 226         {
 227                 free (CtdlThreadStates[i]);
 228         }
 229
 230         /* Clean up the scheduled thread list */
 231         this_thread = CtdlThreadSchedList;
 232         while (this_thread)
 233         {
 234                 that_thread = this_thread;
 235                 this_thread = this_thread->next;
 236                 citthread_mutex_destroy(&that_thread->ThreadMutex);
 237                 citthread_cond_destroy(&that_thread->ThreadCond);
 238                 citthread_mutex_destroy(&that_thread->SleepMutex);
 239                 citthread_cond_destroy(&that_thread->SleepCond);
 240                 citthread_attr_destroy(&that_thread->attr);
 241                 free(that_thread);
 242         }
 243         ctdl_thread_internal_free_tsd();
 244 }
 245
 246 void ctdl_thread_internal_init(void)
 247 {
 248         CtdlThreadNode *this_thread;
 249         int ret = 0;
 250
 251         CtdlThreadStates[CTDL_THREAD_INVALID] = strdup ("Invalid Thread");
 252         CtdlThreadStates[CTDL_THREAD_VALID] = strdup("Valid Thread");
 253         CtdlThreadStates[CTDL_THREAD_CREATE] = strdup("Thread being Created");
 254         CtdlThreadStates[CTDL_THREAD_CANCELLED] = strdup("Thread Cancelled");
 255         CtdlThreadStates[CTDL_THREAD_EXITED] = strdup("Thread Exited");
 256         CtdlThreadStates[CTDL_THREAD_STOPPING] = strdup("Thread Stopping");
 257         CtdlThreadStates[CTDL_THREAD_STOP_REQ] = strdup("Thread Stop Requested");
 258         CtdlThreadStates[CTDL_THREAD_SLEEPING] = strdup("Thread Sleeping");
 259         CtdlThreadStates[CTDL_THREAD_RUNNING] = strdup("Thread Running");
 260         CtdlThreadStates[CTDL_THREAD_BLOCKED] = strdup("Thread Blocked");
 261
 262         /* Get ourself a thread entry */
 263         this_thread = malloc(sizeof(CtdlThreadNode));
 264         if (this_thread == NULL) {
 265                 syslog(LOG_EMERG, "Thread system, can't allocate CtdlThreadNode, exiting\n");
 266                 return;
 267         }
 268         // Ensuring this is zero'd means we make sure the thread doesn't start doing its thing until we are ready.
 269         memset (this_thread, 0, sizeof(CtdlThreadNode));
 270
 271         citthread_mutex_init (&(this_thread->ThreadMutex), NULL);
 272         citthread_cond_init (&(this_thread->ThreadCond), NULL);
 273         citthread_mutex_init (&(this_thread->SleepMutex), NULL);
 274         citthread_cond_init (&(this_thread->SleepCond), NULL);
 275
 276         /* We are garbage collector so create us as running */
 277         this_thread->state = CTDL_THREAD_RUNNING;
 278
 279         if ((ret = citthread_attr_init(&this_thread->attr))) {
 280                 syslog(LOG_EMERG, "Thread system, citthread_attr_init: %s\n", strerror(ret));
 281                 free(this_thread);
 282                 return;
 283         }
 284
 285         this_thread->name = "Garbage Collection Thread";
 286
 287         this_thread->tid = citthread_self();
 288         GC_thread = this_thread;
 289         CT = this_thread;
 290
 291         num_threads++;  // Increase the count of threads in the system.
 292
 293         this_thread->next = CtdlThreadList;
 294         CtdlThreadList = this_thread;
 295         if (this_thread->next)
 296                 this_thread->next->prev = this_thread;
 297         /* Set up start times */
 298         gettimeofday(&this_thread->start_time, NULL);           /* Time this thread started */
 299         memcpy(&this_thread->last_state_change, &this_thread->start_time, sizeof (struct timeval));     /* Changed state so mark it. */
 300 }
 301
 302
 303 /*
 304  * A function to update a threads load averages
 305  */
 306  void ctdl_thread_internal_update_avgs(CtdlThreadNode *this_thread)
 307  {
 308         struct timeval now, result;
 309         double last_duration;
 310
 311         gettimeofday(&now, NULL);
 312         timersub(&now, &(this_thread->last_state_change), &result);
 313         /* I don't think these mutex's are needed here */
 314         citthread_mutex_lock(&this_thread->ThreadMutex);
 315         // result now has a timeval for the time we spent in the last state since we last updated
 316         last_duration = (double)result.tv_sec + ((double)result.tv_usec / (double) 1000000);
 317         if (this_thread->state == CTDL_THREAD_SLEEPING)
 318                 this_thread->avg_sleeping += last_duration;
 319         if (this_thread->state == CTDL_THREAD_RUNNING)
 320                 this_thread->avg_running += last_duration;
 321         if (this_thread->state == CTDL_THREAD_BLOCKED)
 322                 this_thread->avg_blocked += last_duration;
 323         memcpy (&this_thread->last_state_change, &now, sizeof (struct timeval));
 324         citthread_mutex_unlock(&this_thread->ThreadMutex);
 325 }
 326
 327 /*
 328  * A function to chenge the state of a thread
 329  */
 330 void ctdl_thread_internal_change_state (CtdlThreadNode *this_thread, enum CtdlThreadState new_state)
 331 {
 332         /*
 333          * Wether we change state or not we need update the load values
 334          */
 335         ctdl_thread_internal_update_avgs(this_thread);
 336         /* This mutex not needed here? */
 337         citthread_mutex_lock(&this_thread->ThreadMutex); /* To prevent race condition of a sleeping thread */
 338         if ((new_state == CTDL_THREAD_STOP_REQ) && (this_thread->state > CTDL_THREAD_STOP_REQ))
 339                 this_thread->state = new_state;
 340         if (((new_state == CTDL_THREAD_SLEEPING) || (new_state == CTDL_THREAD_BLOCKED)) && (this_thread->state == CTDL_THREAD_RUNNING))
 341                 this_thread->state = new_state;
 342         if ((new_state == CTDL_THREAD_RUNNING) && ((this_thread->state == CTDL_THREAD_SLEEPING) || (this_thread->state == CTDL_THREAD_BLOCKED)))
 343                 this_thread->state = new_state;
 344         citthread_mutex_unlock(&this_thread->ThreadMutex);
 345 }
 346
 347
 348 /*
 349  * A function to tell all threads to exit
 350  */
 351 void CtdlThreadStopAll(void)
 352 {
 353         /* First run any registered shutdown hooks.  This probably doesn't belong here. */
 354         PerformSessionHooks(EVT_SHUTDOWN);
 355
 356         /* then close all tcp ports so nobody else can talk to us anymore. */
 357         CtdlShutdownServiceHooks();
 358         //FIXME: The signalling of the condition should not be in the critical_section
 359         // We need to build a list of threads we are going to signal and then signal them afterwards
 360
 361         ShutDownEventQueue();
 362
 363         CtdlThreadNode *this_thread;
 364
 365         begin_critical_section(S_THREAD_LIST);
 366         this_thread = CtdlThreadList;
 367         // Ask the GC thread to stop first so everything knows we are shutting down.
 368         GC_thread->state = CTDL_THREAD_STOP_REQ;
 369         while(this_thread)
 370         {
 371                 if (!citthread_equal(this_thread->tid, GC_thread->tid))
 372                         citthread_kill(this_thread->tid, SIGHUP);
 373
 374                 ctdl_thread_internal_change_state (this_thread, CTDL_THREAD_STOP_REQ);
 375                 citthread_cond_signal(&this_thread->ThreadCond);
 376                 citthread_cond_signal(&this_thread->SleepCond);
 377                 this_thread->stop_ticker = time(NULL);
 378                 syslog(LOG_DEBUG, "Thread system stopping thread \"%s\" (0x%08lx).\n",
 379                         this_thread->name, this_thread->tid);
 380                 this_thread = this_thread->next;
 381         }
 382         end_critical_section(S_THREAD_LIST);
 383 }
 384
 385
 386 /*
 387  * A function to wake up all sleeping threads
 388  */
 389 void CtdlThreadWakeAll(void)
 390 {
 391         CtdlThreadNode *this_thread;
 392
 393         syslog(LOG_DEBUG, "Thread system waking all threads.\n");
 394
 395         begin_critical_section(S_THREAD_LIST);
 396         this_thread = CtdlThreadList;
 397         while(this_thread)
 398         {
 399                 if (!this_thread->thread_func)
 400                 {
 401                         citthread_cond_signal(&this_thread->ThreadCond);
 402                         citthread_cond_signal(&this_thread->SleepCond);
 403                 }
 404                 this_thread = this_thread->next;
 405         }
 406         end_critical_section(S_THREAD_LIST);
 407 }
 408
 409
 410 /*
 411  * A function to return the number of threads running in the system
 412  */
 413 int CtdlThreadGetCount(void)
 414 {
 415         return  num_threads;
 416 }
 417
 418 int CtdlThreadGetWorkers(void)
 419 {
 420         return  num_workers;
 421 }
 422
 423 double CtdlThreadGetWorkerAvg(void)
 424 {
 425         double ret;
 426
 427         begin_critical_section(S_THREAD_LIST);
 428         ret =  CtdlThreadWorkerAvg;
 429         end_critical_section(S_THREAD_LIST);
 430         return ret;
 431 }
 432
 433 double CtdlThreadGetLoadAvg(void)
 434 {
 435         double load_avg[3] = {0.0, 0.0, 0.0};
 436
 437         int ret = 0;
 438         int smp_num_cpus;
 439
 440         /* Borrowed this straight from procps */
 441         smp_num_cpus = sysconf(_SC_NPROCESSORS_ONLN);
 442         if(smp_num_cpus<1) smp_num_cpus=1; /* SPARC glibc is buggy */
 443
 444 #ifdef HAVE_GETLOADAVG
 445         ret = getloadavg(load_avg, 3);
 446 #endif
 447         if (ret < 0)
 448                 return 0;
 449         return load_avg[0] / smp_num_cpus;
 450 /*
 451  * This old chunk of code return a value that indicated the load on citserver
 452  * This value could easily reach 100 % even when citserver was doing very little and
 453  * hence the machine has much more spare capacity.
 454  * Because this value was used to determine if the machine was under heavy load conditions
 455  * from other processes in the system then citserver could be strangled un-necesarily
 456  * What we are actually trying to achieve is to strangle citserver if the machine is heavily loaded.
 457  * So we have changed this.
 458
 459         begin_critical_section(S_THREAD_LIST);
 460         ret =  CtdlThreadLoadAvg;
 461         end_critical_section(S_THREAD_LIST);
 462         return ret;
 463 */
 464 }
 465
 466
 467
 468
 469 /*
 470  * A function to rename a thread
 471  * Returns a const char *
 472  */
 473 const char *CtdlThreadName(const char *name)
 474 {
 475         const char *old_name;
 476
 477         if (!CT)
 478         {
 479                 syslog(LOG_WARNING, "Thread system WARNING. Attempt to CtdlThreadRename() a non thread. %s\n", name);
 480                 return NULL;
 481         }
 482         old_name = CT->name;
 483         if (name)
 484                 CT->name = name;
 485         return (old_name);
 486 }
 487
 488
 489 /*
 490  * A function to force a thread to exit
 491  */
 492 void CtdlThreadCancel(CtdlThreadNode *thread)
 493 {
 494         CtdlThreadNode *this_thread;
 495
 496         if (!thread)
 497                 this_thread = CT;
 498         else
 499                 this_thread = thread;
 500         if (!this_thread)
 501         {
 502                 syslog(LOG_EMERG, "Thread system PANIC. Attempt to CtdlThreadCancel() a non thread.\n");
 503                 CtdlThreadStopAll();
 504                 return;
 505         }
 506
 507         if (!this_thread->thread_func)
 508         {
 509                 syslog(LOG_EMERG, "Thread system PANIC. Attempt to CtdlThreadCancel() the garbage collector.\n");
 510                 CtdlThreadStopAll();
 511                 return;
 512         }
 513
 514         ctdl_thread_internal_change_state (this_thread, CTDL_THREAD_CANCELLED);
 515         citthread_cancel(this_thread->tid);
 516 }
 517
 518
 519 /*
 520  * A function for a thread to check if it has been asked to stop
 521  */
 522 int CtdlThreadCheckStop(void)
 523 {
 524         int state;
 525
 526         if (!CT)
 527         {
 528                 syslog(LOG_EMERG, "Thread system PANIC, CtdlThreadCheckStop() called by a non thread.\n");
 529                 CtdlThreadStopAll();
 530                 return -1;
 531         }
 532
 533         state = CT->state;
 534
 535         if (CT->signal)
 536         {
 537                 syslog(LOG_DEBUG, "Thread \"%s\" caught signal %d.\n", CT->name, CT->signal);
 538                 if (CT->signal == SIGHUP)
 539                         CT->state = CTDL_THREAD_STOP_REQ;
 540                 CT->signal = 0;
 541         }
 542         if(state == CTDL_THREAD_STOP_REQ)
 543         {
 544                 CT->state = CTDL_THREAD_STOPPING;
 545                 return -1;
 546         }
 547         else if((state < CTDL_THREAD_STOP_REQ) && (state > CTDL_THREAD_CREATE))
 548         {
 549                 return -1;
 550         }
 551         return 0;
 552 }
 553
 554
 555 /*
 556  * A function to ask a thread to exit
 557  * The thread must call CtdlThreadCheckStop() periodically to determine if it should exit
 558  */
 559 void CtdlThreadStop(CtdlThreadNode *thread)
 560 {
 561         CtdlThreadNode *this_thread;
 562
 563         if (!thread)
 564                 this_thread = CT;
 565         else
 566                 this_thread = thread;
 567         if (!this_thread)
 568                 return;
 569         if (!(this_thread->thread_func))
 570                 return;         // Don't stop garbage collector
 571
 572         if (!citthread_equal(this_thread->tid, GC_thread->tid))
 573                 citthread_kill(this_thread->tid, SIGHUP);
 574
 575         ctdl_thread_internal_change_state (this_thread, CTDL_THREAD_STOP_REQ);
 576         citthread_cond_signal(&this_thread->ThreadCond);
 577         citthread_cond_signal(&this_thread->SleepCond);
 578         this_thread->stop_ticker = time(NULL);
 579 }
 580
 581 /*
 582  * So we now have a sleep command that works with threads but it is in seconds
 583  */
 584 void CtdlThreadSleep(int secs)
 585 {
 586         struct timespec wake_time;
 587         struct timeval time_now;
 588
 589
 590         if (!CT)
 591         {
 592                 syslog(LOG_WARNING, "CtdlThreadSleep() called by something that is not a thread. Should we die?\n");
 593                 return;
 594         }
 595
 596         memset (&wake_time, 0, sizeof(struct timespec));
 597         gettimeofday(&time_now, NULL);
 598         wake_time.tv_sec = time_now.tv_sec + secs;
 599         wake_time.tv_nsec = time_now.tv_usec * 10;
 600
 601         ctdl_thread_internal_change_state (CT, CTDL_THREAD_SLEEPING);
 602
 603         citthread_mutex_lock(&CT->ThreadMutex); /* Prevent something asking us to awaken before we've gone to sleep */
 604         citthread_cond_timedwait(&CT->SleepCond, &CT->ThreadMutex, &wake_time);
 605         citthread_mutex_unlock(&CT->ThreadMutex);
 606
 607         ctdl_thread_internal_change_state (CT, CTDL_THREAD_RUNNING);
 608 }
 609
 610
 611 /*
 612  * Routine to clean up our thread function on exit
 613  */
 614 static void ctdl_internal_thread_cleanup(void *arg)
 615 {
 616         /*
 617          * In here we were called by the current thread because it is exiting
 618          * NB. WE ARE THE CURRENT THREAD
 619          */
 620         if (CT)
 621         {
 622                 const char *name = CT->name;
 623                 const pid_t tid = CT->tid;
 624
 625                 syslog(LOG_NOTICE, "Thread \"%s\" (0x%08lx) exited.\n", name, (unsigned long) tid);
 626         }
 627         else
 628         {
 629                 syslog(LOG_NOTICE, "some ((unknown ? ? ?) Thread exited.\n");
 630         }
 631
 632         #ifdef HAVE_BACKTRACE
 633 ///     eCrash_UnregisterThread();
 634         #endif
 635
 636         citthread_mutex_lock(&CT->ThreadMutex);
 637         CT->state = CTDL_THREAD_EXITED; // needs to be last thing else house keeping will unlink us too early
 638         citthread_mutex_unlock(&CT->ThreadMutex);
 639 }
 640
 641 /*
 642  * A quick function to show the load averages
 643  */
 644 void ctdl_thread_internal_calc_loadavg(void)
 645 {
 646         CtdlThreadNode *that_thread;
 647         double load_avg, worker_avg;
 648         int workers = 0;
 649
 650         that_thread = CtdlThreadList;
 651         load_avg = 0;
 652         worker_avg = 0;
 653         while(that_thread)
 654         {
 655                 /* Update load averages */
 656                 ctdl_thread_internal_update_avgs(that_thread);
 657                 citthread_mutex_lock(&that_thread->ThreadMutex);
 658                 that_thread->load_avg = (that_thread->avg_sleeping + that_thread->avg_running) / (that_thread->avg_sleeping + that_thread->avg_running + that_thread->avg_blocked) * 100;
 659                 that_thread->avg_sleeping /= 2;
 660                 that_thread->avg_running /= 2;
 661                 that_thread->avg_blocked /= 2;
 662                 load_avg += that_thread->load_avg;
 663                 if (that_thread->flags & CTDLTHREAD_WORKER)
 664                 {
 665                         worker_avg += that_thread->load_avg;
 666                         workers++;
 667                 }
 668 #ifdef WITH_THREADLOG
 669                 syslog(LOG_DEBUG, "CtdlThread, \"%s\" (%lu) \"%s\" %.2f %.2f %.2f %.2f\n",
 670                         that_thread->name,
 671                         that_thread->tid,
 672                         CtdlThreadStates[that_thread->state],
 673                         that_thread->avg_sleeping,
 674                         that_thread->avg_running,
 675                         that_thread->avg_blocked,
 676                         that_thread->load_avg);
 677 #endif
 678                 citthread_mutex_unlock(&that_thread->ThreadMutex);
 679                 that_thread = that_thread->next;
 680         }
 681         CtdlThreadLoadAvg = load_avg/num_threads;
 682         CtdlThreadWorkerAvg = worker_avg/workers;
 683 #ifdef WITH_THREADLOG
 684         syslog(LOG_INFO, "System load average %.2f, workers averag %.2f, threads %d, workers %d, sessions %d\n", CtdlThreadGetLoadAvg(), CtdlThreadWorkerAvg, num_threads, num_workers, num_sessions);
 685 #endif
 686 }
 687
 688
 689 /*
 690  * Garbage collection routine.
 691  * Gets called by main() in a loop to clean up the thread list periodically.
 692  */
 693 void CtdlThreadGC (void)
 694 {
 695
 696
 697         return;
 698         /* FIXME this is a big deal, but I think it's causing corruption */
 699
 700
 701         CtdlThreadNode *this_thread, *that_thread;
 702         int workers = 0, sys_workers;
 703         int ret=0;
 704
 705         begin_critical_section(S_THREAD_LIST);
 706
 707         /* Handle exiting of garbage collector thread */
 708         if(num_threads == 1)
 709                 CtdlThreadList->state = CTDL_THREAD_EXITED;
 710
 711 #ifdef WITH_THREADLOG
 712         syslog(LOG_DEBUG, "Thread system running garbage collection.\n");
 713 #endif
 714         /*
 715          * Woke up to do garbage collection
 716          */
 717         this_thread = CtdlThreadList;
 718         while(this_thread)
 719         {
 720                 that_thread = this_thread;
 721                 this_thread = this_thread->next;
 722
 723                 if ((that_thread->state == CTDL_THREAD_STOP_REQ || that_thread->state == CTDL_THREAD_STOPPING)
 724                         && (!citthread_equal(that_thread->tid, citthread_self())))
 725                 {
 726                         syslog(LOG_DEBUG, "Waiting for thread %s (0x%08lx) to exit.\n", that_thread->name, that_thread->tid);
 727                         terminate_stuck_sessions();
 728                 }
 729                 else
 730                 {
 731                         /**
 732                          * Catch the situation where a worker was asked to stop but couldn't and we are not
 733                          * shutting down.
 734                          */
 735                         that_thread->stop_ticker = 0;
 736                 }
 737
 738                 if (that_thread->stop_ticker + 5 == time(NULL))
 739                 {
 740                         syslog(LOG_DEBUG, "Thread System: The thread \"%s\" (0x%08lx) failed to self terminate within 5 ticks. It would be cancelled now.\n", that_thread->name, that_thread->tid);
 741                         if ((that_thread->flags & CTDLTHREAD_WORKER) == 0)
 742                                 syslog(LOG_INFO, "Thread System: A non worker thread would have been canceled this may cause message loss.\n");
 743 //                      that_thread->state = CTDL_THREAD_CANCELLED;
 744                         that_thread->stop_ticker++;
 745 //                      citthread_cancel(that_thread->tid);
 746 //                      continue;
 747                 }
 748
 749                 /* Do we need to clean up this thread? */
 750                 if ((that_thread->state != CTDL_THREAD_EXITED) && (that_thread->state != CTDL_THREAD_CANCELLED))
 751                 {
 752                         if(that_thread->flags & CTDLTHREAD_WORKER)
 753                                 workers++;      /* Sanity check on number of worker threads */
 754                         continue;
 755                 }
 756
 757                 if (citthread_equal(that_thread->tid, citthread_self()) && that_thread->thread_func)
 758                 {       /* Sanity check */
 759                         end_critical_section(S_THREAD_LIST);
 760                         syslog(LOG_EMERG, "Thread system PANIC, a thread is trying to clean up after itself.\n");
 761                         abort();
 762                         return;
 763                 }
 764
 765                 if (num_threads <= 0)
 766                 {       /* Sanity check */
 767                         end_critical_section(S_THREAD_LIST);
 768                         syslog(LOG_EMERG, "Thread system PANIC, num_threads <= 0 and trying to do Garbage Collection.\n");
 769                         abort();
 770                         return;
 771                 }
 772
 773                 if(that_thread->flags & CTDLTHREAD_WORKER)
 774                         num_workers--;  /* This is a wroker thread so reduce the count. */
 775                 num_threads--;
 776                 /* If we are unlinking the list head then the next becomes the list head */
 777                 if(that_thread->prev)
 778                         that_thread->prev->next = that_thread->next;
 779                 else
 780                         CtdlThreadList = that_thread->next;
 781                 if(that_thread->next)
 782                         that_thread->next->prev = that_thread->prev;
 783
 784                 citthread_cond_signal(&that_thread->ThreadCond);
 785                 citthread_cond_signal(&that_thread->SleepCond); // Make sure this thread is awake
 786                 citthread_mutex_lock(&that_thread->ThreadMutex);        // Make sure it has done what its doing
 787                 citthread_mutex_unlock(&that_thread->ThreadMutex);
 788                 /*
 789                  * Join on the thread to do clean up and prevent memory leaks
 790                  * Also makes sure the thread has cleaned up after itself before we remove it from the list
 791                  * We can join on the garbage collector thread the join should just return EDEADLCK
 792                  */
 793                 ret = citthread_join (that_thread->tid, NULL);
 794                 if (ret == EDEADLK)
 795                         syslog(LOG_DEBUG, "Garbage collection on own thread.\n");
 796                 else if (ret == EINVAL)
 797                         syslog(LOG_DEBUG, "Garbage collection, that thread already joined on.\n");
 798                 else if (ret == ESRCH)
 799                         syslog(LOG_DEBUG, "Garbage collection, no thread to join on.\n");
 800                 else if (ret != 0)
 801                         syslog(LOG_DEBUG, "Garbage collection, citthread_join returned an unknown error(%d).\n", ret);
 802                 /*
 803                  * Now we own that thread entry
 804                  */
 805                 syslog(LOG_INFO, "Garbage Collection for thread \"%s\" (0x%08lx).\n",
 806                         that_thread->name, that_thread->tid);
 807                 citthread_mutex_destroy(&that_thread->ThreadMutex);
 808                 citthread_cond_destroy(&that_thread->ThreadCond);
 809                 citthread_mutex_destroy(&that_thread->SleepMutex);
 810                 citthread_cond_destroy(&that_thread->SleepCond);
 811                 citthread_attr_destroy(&that_thread->attr);
 812                 free(that_thread);
 813         }
 814         sys_workers = num_workers;
 815         end_critical_section(S_THREAD_LIST);
 816
 817         /* Sanity check number of worker threads */
 818         if (workers != sys_workers)
 819         {
 820                 syslog(LOG_EMERG,
 821                         "Thread system PANIC, discrepancy in number of worker threads. Counted %d, should be %d.\n",
 822                         workers, sys_workers
 823                         );
 824                 abort();
 825         }
 826 }
 827
 828
 829
 830
 831 /*
 832  * Runtime function for a Citadel Thread.
 833  * This initialises the threads environment and then calls the user supplied thread function
 834  * Note that this is the REAL thread function and wraps the users thread function.
 835  */
 836 static void *ctdl_internal_thread_func (void *arg)
 837 {
 838         CtdlThreadNode *this_thread;
 839         void *ret = NULL;
 840
 841         /* lock and unlock the thread list.
 842          * This causes this thread to wait until all its creation stuff has finished before it
 843          * can continue its execution.
 844          */
 845         begin_critical_section(S_THREAD_LIST);
 846         this_thread = (CtdlThreadNode *) arg;
 847         gettimeofday(&this_thread->start_time, NULL);           /* Time this thread started */
 848
 849         // Register the cleanup function to take care of when we exit.
 850         citthread_cleanup_push(ctdl_internal_thread_cleanup, NULL);
 851         // Get our thread data structure
 852         CtdlThreadAllocTSD();
 853         CT = this_thread;
 854         this_thread->pid = getpid();
 855         memcpy(&this_thread->last_state_change, &this_thread->start_time, sizeof (struct timeval));     /* Changed state so mark it. */
 856         /* Only change to running state if we weren't asked to stop during the create cycle
 857          * Other wise there is a window to allow this threads creation to continue to full grown and
 858          * therby prevent a shutdown of the server.
 859          */
 860         if (!CtdlThreadCheckStop())
 861         {
 862                 citthread_mutex_lock(&this_thread->ThreadMutex);
 863                 this_thread->state = CTDL_THREAD_RUNNING;
 864                 citthread_mutex_unlock(&this_thread->ThreadMutex);
 865         }
 866         end_critical_section(S_THREAD_LIST);
 867
 868         // Register for tracing
 869         #ifdef HAVE_BACKTRACE
 870 ///     eCrash_RegisterThread(this_thread->name, 0);
 871         #endif
 872
 873         // Tell the world we are here
 874 #if defined(HAVE_SYSCALL_H) && defined (SYS_gettid)
 875         this_thread->reltid = syscall(SYS_gettid);
 876 #endif
 877         syslog(LOG_NOTICE, "Created a new thread \"%s\" (0x%08lx).\n",
 878                 this_thread->name, this_thread->tid);
 879
 880         /*
 881          * run the thread to do the work but only if we haven't been asked to stop
 882          */
 883         if (!CtdlThreadCheckStop())
 884                 ret = (this_thread->thread_func)(this_thread->user_args);
 885
 886         /*
 887          * Our thread is exiting either because it wanted to end or because the server is stopping
 888          * We need to clean up
 889          */
 890         citthread_cleanup_pop(1);       // Execute our cleanup routine and remove it
 891
 892         return(ret);
 893 }
 894
 895
 896
 897
 898 /*
 899  * Function to initialise an empty thread structure
 900  */
 901 CtdlThreadNode *ctdl_internal_init_thread_struct(CtdlThreadNode *this_thread, long flags)
 902 {
 903         int ret = 0;
 904
 905         // Ensuring this is zero'd means we make sure the thread doesn't start doing its thing until we are ready.
 906         memset (this_thread, 0, sizeof(CtdlThreadNode));
 907
 908         /* Create the mutex's early so we can use them */
 909         citthread_mutex_init (&(this_thread->ThreadMutex), NULL);
 910         citthread_cond_init (&(this_thread->ThreadCond), NULL);
 911         citthread_mutex_init (&(this_thread->SleepMutex), NULL);
 912         citthread_cond_init (&(this_thread->SleepCond), NULL);
 913
 914         this_thread->state = CTDL_THREAD_CREATE;
 915
 916         if ((ret = citthread_attr_init(&this_thread->attr))) {
 917                 citthread_mutex_unlock(&this_thread->ThreadMutex);
 918                 citthread_mutex_destroy(&(this_thread->ThreadMutex));
 919                 citthread_cond_destroy(&(this_thread->ThreadCond));
 920                 citthread_mutex_destroy(&(this_thread->SleepMutex));
 921                 citthread_cond_destroy(&(this_thread->SleepCond));
 922                 syslog(LOG_EMERG, "Thread system, citthread_attr_init: %s\n", strerror(ret));
 923                 free(this_thread);
 924                 return NULL;
 925         }
 926
 927         /* Our per-thread stacks need to be bigger than the default size,
 928          * otherwise the MIME parser crashes on FreeBSD, and the IMAP service
 929          * crashes on 64-bit Linux.
 930          */
 931         if (flags & CTDLTHREAD_BIGSTACK)
 932         {
 933 #ifdef WITH_THREADLOG
 934                 syslog(LOG_INFO, "Thread system. Creating BIG STACK thread.\n");
 935 #endif
 936                 if ((ret = citthread_attr_setstacksize(&this_thread->attr, THREADSTACKSIZE))) {
 937                         citthread_mutex_unlock(&this_thread->ThreadMutex);
 938                         citthread_mutex_destroy(&(this_thread->ThreadMutex));
 939                         citthread_cond_destroy(&(this_thread->ThreadCond));
 940                         citthread_mutex_destroy(&(this_thread->SleepMutex));
 941                         citthread_cond_destroy(&(this_thread->SleepCond));
 942                         citthread_attr_destroy(&this_thread->attr);
 943                         syslog(LOG_EMERG, "Thread system, citthread_attr_setstacksize: %s\n",
 944                                 strerror(ret));
 945                         free(this_thread);
 946                         return NULL;
 947                 }
 948         }
 949
 950         /* Set this new thread with an avg_blocked of 2. We do this so that its creation affects the
 951          * load average for the system. If we don't do this then we create a mass of threads at the same time
 952          * because the creation didn't affect the load average.
 953          */
 954         this_thread->avg_blocked = 2;
 955
 956         return (this_thread);
 957 }
 958
 959
 960
 961
 962 /*
 963  * Internal function to create a thread.
 964  */
 965 CtdlThreadNode *ctdl_internal_create_thread(char *name, long flags, void *(*thread_func) (void *arg), void *args)
 966 {
 967         int ret = 0;
 968         CtdlThreadNode *this_thread;
 969
 970         if (num_threads >= 32767)
 971         {
 972                 syslog(LOG_EMERG, "Thread system. Thread list full.\n");
 973                 return NULL;
 974         }
 975
 976         this_thread = malloc(sizeof(CtdlThreadNode));
 977         if (this_thread == NULL) {
 978                 syslog(LOG_EMERG, "Thread system, can't allocate CtdlThreadNode, exiting\n");
 979                 return NULL;
 980         }
 981
 982         /* Initialise the thread structure */
 983         if (ctdl_internal_init_thread_struct(this_thread, flags) == NULL)
 984         {
 985                 free(this_thread);
 986                 syslog(LOG_EMERG, "Thread system, can't initialise CtdlThreadNode, exiting\n");
 987                 return NULL;
 988         }
 989         /*
 990          * If we got here we are going to create the thread so we must initilise the structure
 991          * first because most implimentations of threading can't create it in a stopped state
 992          * and it might want to do things with its structure that aren't initialised otherwise.
 993          */
 994         if(name)
 995         {
 996                 this_thread->name = name;
 997         }
 998         else
 999         {
1000                 this_thread->name = "Un-named Thread";
1001         }
1002
1003         this_thread->flags = flags;
1004         this_thread->thread_func = thread_func;
1005         this_thread->user_args = args;
1006
1007         begin_critical_section(S_THREAD_LIST);
1008         /*
1009          * We pass this_thread into the thread as its args so that it can find out information
1010          * about itself and it has a bit of storage space for itself, not to mention that the REAL
1011          * thread function needs to finish off the setup of the structure
1012          */
1013         if ((ret = citthread_create(&this_thread->tid, &this_thread->attr, ctdl_internal_thread_func, this_thread) != 0))
1014         {
1015                 end_critical_section(S_THREAD_LIST);
1016                 syslog(LOG_ALERT, "Thread system, Can't create thread: %s\n",
1017                         strerror(ret));
1018                 citthread_mutex_unlock(&this_thread->ThreadMutex);
1019                 citthread_mutex_destroy(&(this_thread->ThreadMutex));
1020                 citthread_cond_destroy(&(this_thread->ThreadCond));
1021                 citthread_mutex_destroy(&(this_thread->SleepMutex));
1022                 citthread_cond_destroy(&(this_thread->SleepCond));
1023                 citthread_attr_destroy(&this_thread->attr);
1024                 free(this_thread);
1025                 return NULL;
1026         }
1027         num_threads++;  // Increase the count of threads in the system.
1028         if(this_thread->flags & CTDLTHREAD_WORKER)
1029                 num_workers++;
1030
1031         this_thread->next = CtdlThreadList;
1032         CtdlThreadList = this_thread;
1033         if (this_thread->next)
1034                 this_thread->next->prev = this_thread;
1035         ctdl_thread_internal_calc_loadavg();
1036
1037         end_critical_section(S_THREAD_LIST);
1038
1039         return this_thread;
1040 }
1041
1042 /*
1043  * Wrapper function to create a thread
1044  * ensures the critical section and other protections are in place.
1045  * char *name = name to give to thread, if NULL, use generic name
1046  * int flags = flags to determine type of thread and standard facilities
1047  */
1048 CtdlThreadNode *CtdlThreadCreate(char *name, long flags, void *(*thread_func) (void *arg), void *args)
1049 {
1050         CtdlThreadNode *ret = NULL;
1051
1052         ret = ctdl_internal_create_thread(name, flags, thread_func, args);
1053         return ret;
1054 }
1055
1056
1057
1058 CtdlThreadNode *ctdl_thread_internal_start_scheduled (CtdlThreadNode *this_thread)
1059 {
1060         int ret = 0;
1061
1062         begin_critical_section(S_THREAD_LIST);
1063         /*
1064          * We pass this_thread into the thread as its args so that it can find out information
1065          * about itself and it has a bit of storage space for itself, not to mention that the REAL
1066          * thread function needs to finish off the setup of the structure
1067          */
1068         if ((ret = citthread_create(&this_thread->tid, &this_thread->attr, ctdl_internal_thread_func, this_thread) != 0))
1069         {
1070                 end_critical_section(S_THREAD_LIST);
1071                 syslog(LOG_DEBUG, "Failed to start scheduled thread \"%s\": %s\n", this_thread->name, strerror(ret));
1072                 citthread_mutex_destroy(&(this_thread->ThreadMutex));
1073                 citthread_cond_destroy(&(this_thread->ThreadCond));
1074                 citthread_mutex_destroy(&(this_thread->SleepMutex));
1075                 citthread_cond_destroy(&(this_thread->SleepCond));
1076                 citthread_attr_destroy(&this_thread->attr);
1077                 free(this_thread);
1078                 return NULL;
1079         }
1080
1081
1082         num_threads++;  // Increase the count of threads in the system.
1083         if(this_thread->flags & CTDLTHREAD_WORKER)
1084                 num_workers++;
1085
1086         this_thread->next = CtdlThreadList;
1087         CtdlThreadList = this_thread;
1088         if (this_thread->next)
1089                 this_thread->next->prev = this_thread;
1090
1091         ctdl_thread_internal_calc_loadavg();
1092         end_critical_section(S_THREAD_LIST);
1093
1094
1095         return this_thread;
1096 }
1097
1098
1099
1100 void ctdl_thread_internal_check_scheduled(void)
1101 {
1102         CtdlThreadNode *this_thread, *that_thread;
1103         time_t now;
1104
1105         /* Don't start scheduled threads if the system wants single user mode */
1106         if (CtdlWantSingleUser())
1107                 return;
1108
1109         if (try_critical_section(S_SCHEDULE_LIST))
1110                 return; /* If this list is locked we wait till the next chance */
1111
1112         now = time(NULL);
1113
1114 #ifdef WITH_THREADLOG
1115         syslog(LOG_DEBUG, "Checking for scheduled threads to start.\n");
1116 #endif
1117
1118         this_thread = CtdlThreadSchedList;
1119         while(this_thread)
1120         {
1121                 that_thread = this_thread;
1122                 this_thread = this_thread->next;
1123
1124                 if (now > that_thread->when)
1125                 {
1126                         /* Unlink from schedule list */
1127                         if (that_thread->prev)
1128                                 that_thread->prev->next = that_thread->next;
1129                         else
1130                                 CtdlThreadSchedList = that_thread->next;
1131                         if (that_thread->next)
1132                                 that_thread->next->prev = that_thread->prev;
1133
1134                         that_thread->next = that_thread->prev = NULL;
1135 #ifdef WITH_THREADLOG
1136                         syslog(LOG_DEBUG, "About to start scheduled thread \"%s\".\n", that_thread->name);
1137 #endif
1138                         if (CT->state > CTDL_THREAD_STOP_REQ)
1139                         {       /* Only start it if the system is not stopping */
1140                                 if (ctdl_thread_internal_start_scheduled (that_thread))
1141                                 {
1142 #ifdef WITH_THREADLOG
1143                                         syslog(LOG_INFO, "Thread system, Started a scheduled thread \"%s\" (0x%08lx).\n",
1144                                                 that_thread->name, that_thread->tid);
1145 #endif
1146                                 }
1147                         }
1148                 }
1149 #ifdef WITH_THREADLOG
1150                 else
1151                 {
1152                         syslog(LOG_DEBUG, "Thread \"%s\" will start in %ld seconds.\n",
1153                                 that_thread->name, that_thread->when - time(NULL));
1154                 }
1155 #endif
1156         }
1157         end_critical_section(S_SCHEDULE_LIST);
1158 }
1159
1160
1161 /*
1162  * A warapper function for select so we can show a thread as blocked
1163  */
1164 int CtdlThreadSelect(int n, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout)
1165 {
1166         int ret = 0;
1167
1168         ctdl_thread_internal_change_state(CT, CTDL_THREAD_BLOCKED);
1169         if (!CtdlThreadCheckStop())
1170                 ret = select(n, readfds, writefds, exceptfds, timeout);
1171         /**
1172          * If the select returned <= 0 then it failed due to an error
1173          * or timeout so this thread could stop if asked to do so.
1174          * Anything else means it needs to continue unless the system is shutting down
1175          */
1176         if (ret > 0)
1177         {
1178                 /**
1179                  * The select says this thread needs to do something useful.
1180                  * This thread was in an idle state so it may have been asked to stop
1181                  * but if the system isn't shutting down this thread is no longer
1182                  * idle and select has given it a task to do so it must not stop
1183                  * In this condition we need to force it into the running state.
1184                  * CtdlThreadGC will clear its ticker for us.
1185                  *
1186                  * FIXME: there is still a small hole here. It is possible for the sequence of locking
1187                  * to allow the state to get changed to STOP_REQ just after this code if the other thread
1188                  * has decided to change the state before this lock, it there fore has to wait till the lock
1189                  * completes but it will continue to change the state. We need something a bit better here.
1190                  */
1191                 citthread_mutex_lock(&CT->ThreadMutex); /* To prevent race condition of a sleeping thread */
1192                 if (GC_thread->state > CTDL_THREAD_STOP_REQ && CT->state <= CTDL_THREAD_STOP_REQ)
1193                 {
1194                         syslog(LOG_DEBUG, "Thread %s (0x%08lx) refused stop request.\n", CT->name, CT->tid);
1195                         CT->state = CTDL_THREAD_RUNNING;
1196                 }
1197                 citthread_mutex_unlock(&CT->ThreadMutex);
1198         }
1199
1200         ctdl_thread_internal_change_state(CT, CTDL_THREAD_RUNNING);
1201
1202         return ret;
1203 }
1204
1205
1206
1207 void *new_worker_thread(void *arg);
1208 extern void close_masters (void);
1209
1210
1211
1212 void go_threading(void)
1213 {
1214         int i;
1215         CtdlThreadNode *last_worker;
1216         struct timeval start, now, result;
1217         double last_duration;
1218
1219         /*
1220          * Initialise the thread system
1221          */
1222         ctdl_thread_internal_init();
1223
1224         /* Second call to module init functions now that threading is up */
1225         initialise_modules(1);
1226         CtdlThreadCreate("select_on_master", CTDLTHREAD_BIGSTACK, select_on_master, NULL);
1227
1228         /*
1229          * This thread is now used for garbage collection of other threads in the thread list
1230          */
1231         syslog(LOG_INFO, "Startup thread %ld becoming garbage collector,\n", (long) citthread_self());
1232
1233         /*
1234          * We do a lot of locking and unlocking of the thread list in here.
1235          * We do this so that we can repeatedly release time for other threads
1236          * that may be waiting on the thread list.
1237          * We are a low priority thread so we can afford to do this
1238          */
1239
1240         while (CtdlThreadGetCount())
1241         {
1242                 if (CT->signal)
1243                         exit_signal = CT->signal;
1244                 if (exit_signal)
1245                 {
1246                         CtdlThreadStopAll();
1247                 }
1248                 check_sched_shutdown();
1249                 if (CT->state > CTDL_THREAD_STOP_REQ)
1250                 {
1251                         begin_critical_section(S_THREAD_LIST);
1252                         ctdl_thread_internal_calc_loadavg();
1253                         end_critical_section(S_THREAD_LIST);
1254
1255                         ctdl_thread_internal_check_scheduled(); /* start scheduled threads */
1256                 }
1257
1258                 /* Reduce the size of the worker thread pool if necessary. */
1259                 if ((CtdlThreadGetWorkers() > config.c_min_workers + 1) && (CtdlThreadWorkerAvg < 20) && (CT->state > CTDL_THREAD_STOP_REQ))
1260                 {
1261                         /* Ask a worker thread to stop as we no longer need it */
1262                         begin_critical_section(S_THREAD_LIST);
1263                         last_worker = CtdlThreadList;
1264                         while (last_worker)
1265                         {
1266                                 citthread_mutex_lock(&last_worker->ThreadMutex);
1267                                 if (last_worker->flags & CTDLTHREAD_WORKER && (last_worker->state > CTDL_THREAD_STOPPING) && (last_worker->Context == NULL))
1268                                 {
1269                                         citthread_mutex_unlock(&last_worker->ThreadMutex);
1270                                         break;
1271                                 }
1272                                 citthread_mutex_unlock(&last_worker->ThreadMutex);
1273                                 last_worker = last_worker->next;
1274                         }
1275                         end_critical_section(S_THREAD_LIST);
1276                         if (last_worker)
1277                         {
1278 #ifdef WITH_THREADLOG
1279                                 syslog(LOG_DEBUG, "Thread system, stopping excess worker thread \"%s\" (0x%08lx).\n",
1280                                         last_worker->name,
1281                                         last_worker->tid
1282                                         );
1283 #endif
1284                                 CtdlThreadStop(last_worker);
1285                         }
1286                 }
1287
1288                 /*
1289                  * If all our workers are working hard, start some more to help out
1290                  * with things
1291                  */
1292                 /* FIXME: come up with a better way to dynamically alter the number of threads
1293                  * based on the system load
1294                  */
1295                 if (    (((CtdlThreadGetWorkers() < config.c_max_workers)
1296                         && (CtdlThreadGetWorkerAvg() > 60))
1297                         || CtdlThreadGetWorkers() < config.c_min_workers)
1298                         && (CT->state > CTDL_THREAD_STOP_REQ)
1299                 )
1300                 {
1301                         /* Only start new threads if we are not going to overload the machine */
1302                         /* Temporarily set to 10 should be enough to make sure we don't stranglew the server
1303                          * at least until we make this a config option */
1304                         if (CtdlThreadGetLoadAvg() < ((double)10.00)) {
1305                                 for (i=0; i<5 ; i++) {
1306                                         CtdlThreadCreate("Worker Thread",
1307                                                 CTDLTHREAD_BIGSTACK + CTDLTHREAD_WORKER,
1308                                                 worker_thread,
1309                                                 NULL
1310                                                 );
1311                                 }
1312                         }
1313                         else
1314                                 syslog(LOG_WARNING, "Server strangled due to machine load average too high.\n");
1315                 }
1316
1317                 CtdlThreadGC();
1318
1319                 if (CtdlThreadGetCount() <= 1) // Shutting down clean up the garbage collector
1320                 {
1321                         CtdlThreadGC();
1322                 }
1323
1324 #ifdef THREADS_USESIGNALS
1325                 if (CtdlThreadGetCount() && CT->state > CTDL_THREAD_STOP_REQ)
1326 #else
1327                 if (CtdlThreadGetCount())
1328 #endif
1329                         CtdlThreadSleep(1);
1330         }
1331         /*
1332          * If the above loop exits we must be shutting down since we obviously have no threads
1333          */
1334         ctdl_thread_internal_cleanup();
1335 }
1336
1337
1338
1339