lib/fuse_loop_mt.c

   1 /*
   2   FUSE: Filesystem in Userspace
   3   Copyright (C) 2001-2007  Miklos Szeredi <miklos@szeredi.hu>
   4
   5   This program can be distributed under the terms of the GNU LGPLv2.
   6   See the file COPYING.LIB.
   7 */
   8
   9 #include "fuse_lowlevel.h"
  10 #include "fuse_misc.h"
  11 #include "fuse_kernel.h"
  12 #include "fuse_i.h"
  13
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16 #include <string.h>
  17 #include <unistd.h>
  18 #include <signal.h>
  19 #include <semaphore.h>
  20 #include <errno.h>
  21 #include <sys/time.h>
  22
  23 /* Environment var controlling the thread stack size */
  24 #define ENVNAME_THREAD_STACK "FUSE_THREAD_STACK"
  25
  26 struct fuse_worker {
  27         struct fuse_worker *prev;
  28         struct fuse_worker *next;
  29         pthread_t thread_id;
  30         size_t bufsize;
  31         char *buf;
  32         struct fuse_mt *mt;
  33 };
  34
  35 struct fuse_mt {
  36         pthread_mutex_t lock;
  37         int numworker;
  38         int numavail;
  39         struct fuse_session *se;
  40         struct fuse_chan *prevch;
  41         struct fuse_worker main;
  42         sem_t finish;
  43         int exit;
  44         int error;
  45 };
  46
  47 static void list_add_worker(struct fuse_worker *w, struct fuse_worker *next)
  48 {
  49         struct fuse_worker *prev = next->prev;
  50         w->next = next;
  51         w->prev = prev;
  52         prev->next = w;
  53         next->prev = w;
  54 }
  55
  56 static void list_del_worker(struct fuse_worker *w)
  57 {
  58         struct fuse_worker *prev = w->prev;
  59         struct fuse_worker *next = w->next;
  60         prev->next = next;
  61         next->prev = prev;
  62 }
  63
  64 static int fuse_loop_start_thread(struct fuse_mt *mt);
  65
  66 static void *fuse_do_work(void *data)
  67 {
  68         struct fuse_worker *w = (struct fuse_worker *) data;
  69         struct fuse_mt *mt = w->mt;
  70
  71         while (!fuse_session_exited(mt->se)) {
  72                 int isforget = 0;
  73                 struct fuse_chan *ch = mt->prevch;
  74                 struct fuse_buf fbuf = {
  75                         .mem = w->buf,
  76                         .size = w->bufsize,
  77                 };
  78                 int res;
  79
  80                 pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
  81                 res = fuse_session_receive_buf(mt->se, &fbuf, &ch);
  82                 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
  83                 if (res == -EINTR)
  84                         continue;
  85                 if (res <= 0) {
  86                         if (res < 0) {
  87                                 fuse_session_exit(mt->se);
  88                                 mt->error = -1;
  89                         }
  90                         break;
  91                 }
  92
  93                 pthread_mutex_lock(&mt->lock);
  94                 if (mt->exit) {
  95                         pthread_mutex_unlock(&mt->lock);
  96                         return NULL;
  97                 }
  98
  99                 /*
 100                  * This disgusting hack is needed so that zillions of threads
 101                  * are not created on a burst of FORGET messages
 102                  */
 103                 if (!(fbuf.flags & FUSE_BUF_IS_FD)) {
 104                         struct fuse_in_header *in = fbuf.mem;
 105
 106                         if (in->opcode == FUSE_FORGET ||
 107                             in->opcode == FUSE_BATCH_FORGET)
 108                                 isforget = 1;
 109                 }
 110
 111                 if (!isforget)
 112                         mt->numavail--;
 113                 if (mt->numavail == 0)
 114                         fuse_loop_start_thread(mt);
 115                 pthread_mutex_unlock(&mt->lock);
 116
 117                 fuse_session_process_buf(mt->se, &fbuf, ch);
 118
 119                 pthread_mutex_lock(&mt->lock);
 120                 if (!isforget)
 121                         mt->numavail++;
 122                 if (mt->numavail > 10) {
 123                         if (mt->exit) {
 124                                 pthread_mutex_unlock(&mt->lock);
 125                                 return NULL;
 126                         }
 127                         list_del_worker(w);
 128                         mt->numavail--;
 129                         mt->numworker--;
 130                         pthread_mutex_unlock(&mt->lock);
 131
 132                         pthread_detach(w->thread_id);
 133                         free(w->buf);
 134                         free(w);
 135                         return NULL;
 136                 }
 137                 pthread_mutex_unlock(&mt->lock);
 138         }
 139
 140         sem_post(&mt->finish);
 141
 142         return NULL;
 143 }
 144
 145 int fuse_start_thread(pthread_t *thread_id, void *(*func)(void *), void *arg)
 146 {
 147         sigset_t oldset;
 148         sigset_t newset;
 149         int res;
 150         pthread_attr_t attr;
 151         char *stack_size;
 152
 153         /* Override default stack size */
 154         pthread_attr_init(&attr);
 155         stack_size = getenv(ENVNAME_THREAD_STACK);
 156         if (stack_size && pthread_attr_setstacksize(&attr, atoi(stack_size)))
 157                 fprintf(stderr, "fuse: invalid stack size: %s\n", stack_size);
 158
 159         /* Disallow signal reception in worker threads */
 160         sigemptyset(&newset);
 161         sigaddset(&newset, SIGTERM);
 162         sigaddset(&newset, SIGINT);
 163         sigaddset(&newset, SIGHUP);
 164         sigaddset(&newset, SIGQUIT);
 165         pthread_sigmask(SIG_BLOCK, &newset, &oldset);
 166         res = pthread_create(thread_id, &attr, func, arg);
 167         pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 168         pthread_attr_destroy(&attr);
 169         if (res != 0) {
 170                 fprintf(stderr, "fuse: error creating thread: %s\n",
 171                         strerror(res));
 172                 return -1;
 173         }
 174
 175         return 0;
 176 }
 177
 178 static int fuse_loop_start_thread(struct fuse_mt *mt)
 179 {
 180         int res;
 181         struct fuse_worker *w = malloc(sizeof(struct fuse_worker));
 182         if (!w) {
 183                 fprintf(stderr, "fuse: failed to allocate worker structure\n");
 184                 return -1;
 185         }
 186         memset(w, 0, sizeof(struct fuse_worker));
 187         w->bufsize = fuse_chan_bufsize(mt->prevch);
 188         w->buf = malloc(w->bufsize);
 189         w->mt = mt;
 190         if (!w->buf) {
 191                 fprintf(stderr, "fuse: failed to allocate read buffer\n");
 192                 free(w);
 193                 return -1;
 194         }
 195
 196         res = fuse_start_thread(&w->thread_id, fuse_do_work, w);
 197         if (res == -1) {
 198                 free(w->buf);
 199                 free(w);
 200                 return -1;
 201         }
 202         list_add_worker(w, &mt->main);
 203         mt->numavail ++;
 204         mt->numworker ++;
 205
 206         return 0;
 207 }
 208
 209 static void fuse_join_worker(struct fuse_mt *mt, struct fuse_worker *w)
 210 {
 211         pthread_join(w->thread_id, NULL);
 212         pthread_mutex_lock(&mt->lock);
 213         list_del_worker(w);
 214         pthread_mutex_unlock(&mt->lock);
 215         free(w->buf);
 216         free(w);
 217 }
 218
 219 int fuse_session_loop_mt(struct fuse_session *se)
 220 {
 221         int err;
 222         struct fuse_mt mt;
 223         struct fuse_worker *w;
 224
 225         memset(&mt, 0, sizeof(struct fuse_mt));
 226         mt.se = se;
 227         mt.prevch = fuse_session_next_chan(se, NULL);
 228         mt.error = 0;
 229         mt.numworker = 0;
 230         mt.numavail = 0;
 231         mt.main.thread_id = pthread_self();
 232         mt.main.prev = mt.main.next = &mt.main;
 233         sem_init(&mt.finish, 0, 0);
 234         fuse_mutex_init(&mt.lock);
 235
 236         pthread_mutex_lock(&mt.lock);
 237         err = fuse_loop_start_thread(&mt);
 238         pthread_mutex_unlock(&mt.lock);
 239         if (!err) {
 240                 /* sem_wait() is interruptible */
 241                 while (!fuse_session_exited(se))
 242                         sem_wait(&mt.finish);
 243
 244                 for (w = mt.main.next; w != &mt.main; w = w->next)
 245                         pthread_cancel(w->thread_id);
 246                 mt.exit = 1;
 247
 248                 while (mt.main.next != &mt.main)
 249                         fuse_join_worker(&mt, mt.main.next);
 250
 251                 err = mt.error;
 252         }
 253
 254         pthread_mutex_destroy(&mt.lock);
 255         sem_destroy(&mt.finish);
 256         fuse_session_reset(se);
 257         return err;
 258 }