mono/sgen/sgen-thread-pool.c

   1 /*
   2  * sgen-thread-pool.c: Threadpool for all concurrent GC work.
   3  *
   4  * Copyright (C) 2015 Xamarin Inc
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Library General Public
   8  * License 2.0 as published by the Free Software Foundation;
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Library General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Library General Public
  16  * License 2.0 along with this library; if not, write to the Free
  17  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18  */
  19
  20 #include "config.h"
  21 #ifdef HAVE_SGEN_GC
  22
  23 #include "mono/sgen/sgen-gc.h"
  24 #include "mono/sgen/sgen-thread-pool.h"
  25 #include "mono/sgen/sgen-pointer-queue.h"
  26 #include "mono/utils/mono-os-mutex.h"
  27 #ifndef SGEN_WITHOUT_MONO
  28 #include "mono/utils/mono-threads.h"
  29 #endif
  30
  31 static mono_mutex_t lock;
  32 static mono_cond_t work_cond;
  33 static mono_cond_t done_cond;
  34
  35 static MonoNativeThreadId thread;
  36
  37 /* Only accessed with the lock held. */
  38 static SgenPointerQueue job_queue;
  39
  40 static SgenThreadPoolThreadInitFunc thread_init_func;
  41 static SgenThreadPoolIdleJobFunc idle_job_func;
  42 static SgenThreadPoolContinueIdleJobFunc continue_idle_job_func;
  43
  44 enum {
  45         STATE_WAITING,
  46         STATE_IN_PROGRESS,
  47         STATE_DONE
  48 };
  49
  50 /* Assumes that the lock is held. */
  51 static SgenThreadPoolJob*
  52 get_job_and_set_in_progress (void)
  53 {
  54         for (size_t i = 0; i < job_queue.next_slot; ++i) {
  55                 SgenThreadPoolJob *job = (SgenThreadPoolJob *)job_queue.data [i];
  56                 if (job->state == STATE_WAITING) {
  57                         job->state = STATE_IN_PROGRESS;
  58                         return job;
  59                 }
  60         }
  61         return NULL;
  62 }
  63
  64 /* Assumes that the lock is held. */
  65 static ssize_t
  66 find_job_in_queue (SgenThreadPoolJob *job)
  67 {
  68         for (ssize_t i = 0; i < job_queue.next_slot; ++i) {
  69                 if (job_queue.data [i] == job)
  70                         return i;
  71         }
  72         return -1;
  73 }
  74
  75 /* Assumes that the lock is held. */
  76 static void
  77 remove_job (SgenThreadPoolJob *job)
  78 {
  79         ssize_t index;
  80         SGEN_ASSERT (0, job->state == STATE_DONE, "Why are we removing a job that's not done?");
  81         index = find_job_in_queue (job);
  82         SGEN_ASSERT (0, index >= 0, "Why is the job we're trying to remove not in the queue?");
  83         job_queue.data [index] = NULL;
  84         sgen_pointer_queue_remove_nulls (&job_queue);
  85         sgen_thread_pool_job_free (job);
  86 }
  87
  88 static gboolean
  89 continue_idle_job (void)
  90 {
  91         if (!continue_idle_job_func)
  92                 return FALSE;
  93         return continue_idle_job_func ();
  94 }
  95
  96 static mono_native_thread_return_t
  97 thread_func (void *thread_data)
  98 {
  99         thread_init_func (thread_data);
 100
 101         mono_os_mutex_lock (&lock);
 102         for (;;) {
 103                 /*
 104                  * It's important that we check the continue idle flag with the lock held.
 105                  * Suppose we didn't check with the lock held, and the result is FALSE.  The
 106                  * main thread might then set continue idle and signal us before we can take
 107                  * the lock, and we'd lose the signal.
 108                  */
 109                 gboolean do_idle = continue_idle_job ();
 110                 SgenThreadPoolJob *job = get_job_and_set_in_progress ();
 111
 112                 if (!job && !do_idle) {
 113                         /*
 114                          * pthread_cond_wait() can return successfully despite the condition
 115                          * not being signalled, so we have to run this in a loop until we
 116                          * really have work to do.
 117                          */
 118                         mono_os_cond_wait (&work_cond, &lock);
 119                         continue;
 120                 }
 121
 122                 mono_os_mutex_unlock (&lock);
 123
 124                 if (job) {
 125                         job->func (thread_data, job);
 126
 127                         mono_os_mutex_lock (&lock);
 128
 129                         SGEN_ASSERT (0, job->state == STATE_IN_PROGRESS, "The job should still be in progress.");
 130                         job->state = STATE_DONE;
 131                         remove_job (job);
 132                         /*
 133                          * Only the main GC thread will ever wait on the done condition, so we don't
 134                          * have to broadcast.
 135                          */
 136                         mono_os_cond_signal (&done_cond);
 137                 } else {
 138                         SGEN_ASSERT (0, do_idle, "Why did we unlock if we still have to wait for idle?");
 139                         SGEN_ASSERT (0, idle_job_func, "Why do we have idle work when there's no idle job function?");
 140                         do {
 141                                 idle_job_func (thread_data);
 142                                 do_idle = continue_idle_job ();
 143                         } while (do_idle && !job_queue.next_slot);
 144
 145                         mono_os_mutex_lock (&lock);
 146
 147                         if (!do_idle)
 148                                 mono_os_cond_signal (&done_cond);
 149                 }
 150         }
 151
 152         return (mono_native_thread_return_t)0;
 153 }
 154
 155 void
 156 sgen_thread_pool_init (int num_threads, SgenThreadPoolThreadInitFunc init_func, SgenThreadPoolIdleJobFunc idle_func, SgenThreadPoolContinueIdleJobFunc continue_idle_func, void **thread_datas)
 157 {
 158         SGEN_ASSERT (0, num_threads == 1, "We only support 1 thread pool thread for now.");
 159
 160         mono_os_mutex_init (&lock);
 161         mono_os_cond_init (&work_cond);
 162         mono_os_cond_init (&done_cond);
 163
 164         thread_init_func = init_func;
 165         idle_job_func = idle_func;
 166         continue_idle_job_func = continue_idle_func;
 167
 168         mono_native_thread_create (&thread, thread_func, thread_datas ? thread_datas [0] : NULL);
 169 }
 170
 171 SgenThreadPoolJob*
 172 sgen_thread_pool_job_alloc (const char *name, SgenThreadPoolJobFunc func, size_t size)
 173 {
 174         SgenThreadPoolJob *job = (SgenThreadPoolJob *)sgen_alloc_internal_dynamic (size, INTERNAL_MEM_THREAD_POOL_JOB, TRUE);
 175         job->name = name;
 176         job->size = size;
 177         job->state = STATE_WAITING;
 178         job->func = func;
 179         return job;
 180 }
 181
 182 void
 183 sgen_thread_pool_job_free (SgenThreadPoolJob *job)
 184 {
 185         sgen_free_internal_dynamic (job, job->size, INTERNAL_MEM_THREAD_POOL_JOB);
 186 }
 187
 188 void
 189 sgen_thread_pool_job_enqueue (SgenThreadPoolJob *job)
 190 {
 191         mono_os_mutex_lock (&lock);
 192
 193         sgen_pointer_queue_add (&job_queue, job);
 194         /*
 195          * FIXME: We could check whether there is a job in progress.  If there is, there's
 196          * no need to signal the condition, at least as long as we have only one thread.
 197          */
 198         mono_os_cond_signal (&work_cond);
 199
 200         mono_os_mutex_unlock (&lock);
 201 }
 202
 203 void
 204 sgen_thread_pool_job_wait (SgenThreadPoolJob *job)
 205 {
 206         SGEN_ASSERT (0, job, "Where's the job?");
 207
 208         mono_os_mutex_lock (&lock);
 209
 210         while (find_job_in_queue (job) >= 0)
 211                 mono_os_cond_wait (&done_cond, &lock);
 212
 213         mono_os_mutex_unlock (&lock);
 214 }
 215
 216 void
 217 sgen_thread_pool_idle_signal (void)
 218 {
 219         SGEN_ASSERT (0, idle_job_func, "Why are we signaling idle without an idle function?");
 220
 221         mono_os_mutex_lock (&lock);
 222
 223         if (continue_idle_job_func ())
 224                 mono_os_cond_signal (&work_cond);
 225
 226         mono_os_mutex_unlock (&lock);
 227 }
 228
 229 void
 230 sgen_thread_pool_idle_wait (void)
 231 {
 232         SGEN_ASSERT (0, idle_job_func, "Why are we waiting for idle without an idle function?");
 233
 234         mono_os_mutex_lock (&lock);
 235
 236         while (continue_idle_job_func ())
 237                 mono_os_cond_wait (&done_cond, &lock);
 238
 239         mono_os_mutex_unlock (&lock);
 240 }
 241
 242 void
 243 sgen_thread_pool_wait_for_all_jobs (void)
 244 {
 245         mono_os_mutex_lock (&lock);
 246
 247         while (!sgen_pointer_queue_is_empty (&job_queue))
 248                 mono_os_cond_wait (&done_cond, &lock);
 249
 250         mono_os_mutex_unlock (&lock);
 251 }
 252
 253 gboolean
 254 sgen_thread_pool_is_thread_pool_thread (MonoNativeThreadId some_thread)
 255 {
 256         return some_thread == thread;
 257 }
 258
 259 #endif