arch/um/os-Linux/sigio.c

   1 /*
   2  * Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <unistd.h>
   7 #include <stdlib.h>
   8 #include <termios.h>
   9 #include <pty.h>
  10 #include <signal.h>
  11 #include <errno.h>
  12 #include <string.h>
  13 #include <sched.h>
  14 #include <sys/socket.h>
  15 #include <sys/poll.h>
  16 #include "init.h"
  17 #include "user.h"
  18 #include "kern_util.h"
  19 #include "user_util.h"
  20 #include "sigio.h"
  21 #include "os.h"
  22
  23 /* Protected by sigio_lock(), also used by sigio_cleanup, which is an
  24  * exitcall.
  25  */
  26 static int write_sigio_pid = -1;
  27
  28 /* These arrays are initialized before the sigio thread is started, and
  29  * the descriptors closed after it is killed.  So, it can't see them change.
  30  * On the UML side, they are changed under the sigio_lock.
  31  */
  32 #define SIGIO_FDS_INIT {-1, -1}
  33
  34 static int write_sigio_fds[2] = SIGIO_FDS_INIT;
  35 static int sigio_private[2] = SIGIO_FDS_INIT;
  36
  37 struct pollfds {
  38         struct pollfd *poll;
  39         int size;
  40         int used;
  41 };
  42
  43 /* Protected by sigio_lock().  Used by the sigio thread, but the UML thread
  44  * synchronizes with it.
  45  */
  46 struct pollfds current_poll = {
  47         .poll           = NULL,
  48         .size           = 0,
  49         .used           = 0
  50 };
  51
  52 struct pollfds next_poll = {
  53         .poll           = NULL,
  54         .size           = 0,
  55         .used           = 0
  56 };
  57
  58 static int write_sigio_thread(void *unused)
  59 {
  60         struct pollfds *fds, tmp;
  61         struct pollfd *p;
  62         int i, n, respond_fd;
  63         char c;
  64
  65         signal(SIGWINCH, SIG_IGN);
  66         fds = &current_poll;
  67         while(1){
  68                 n = poll(fds->poll, fds->used, -1);
  69                 if(n < 0){
  70                         if(errno == EINTR) continue;
  71                         printk("write_sigio_thread : poll returned %d, "
  72                                "errno = %d\n", n, errno);
  73                 }
  74                 for(i = 0; i < fds->used; i++){
  75                         p = &fds->poll[i];
  76                         if(p->revents == 0) continue;
  77                         if(p->fd == sigio_private[1]){
  78                                 n = os_read_file(sigio_private[1], &c, sizeof(c));
  79                                 if(n != sizeof(c))
  80                                         printk("write_sigio_thread : "
  81                                                "read failed, err = %d\n", -n);
  82                                 tmp = current_poll;
  83                                 current_poll = next_poll;
  84                                 next_poll = tmp;
  85                                 respond_fd = sigio_private[1];
  86                         }
  87                         else {
  88                                 respond_fd = write_sigio_fds[1];
  89                                 fds->used--;
  90                                 memmove(&fds->poll[i], &fds->poll[i + 1],
  91                                         (fds->used - i) * sizeof(*fds->poll));
  92                         }
  93
  94                         n = os_write_file(respond_fd, &c, sizeof(c));
  95                         if(n != sizeof(c))
  96                                 printk("write_sigio_thread : write failed, "
  97                                        "err = %d\n", -n);
  98                 }
  99         }
 100
 101         return 0;
 102 }
 103
 104 static int need_poll(int n)
 105 {
 106         if(n <= next_poll.size){
 107                 next_poll.used = n;
 108                 return(0);
 109         }
 110         kfree(next_poll.poll);
 111         next_poll.poll = um_kmalloc_atomic(n * sizeof(struct pollfd));
 112         if(next_poll.poll == NULL){
 113                 printk("need_poll : failed to allocate new pollfds\n");
 114                 next_poll.size = 0;
 115                 next_poll.used = 0;
 116                 return(-1);
 117         }
 118         next_poll.size = n;
 119         next_poll.used = n;
 120         return(0);
 121 }
 122
 123 /* Must be called with sigio_lock held, because it's needed by the marked
 124  * critical section. */
 125 static void update_thread(void)
 126 {
 127         unsigned long flags;
 128         int n;
 129         char c;
 130
 131         flags = set_signals(0);
 132         n = os_write_file(sigio_private[0], &c, sizeof(c));
 133         if(n != sizeof(c)){
 134                 printk("update_thread : write failed, err = %d\n", -n);
 135                 goto fail;
 136         }
 137
 138         n = os_read_file(sigio_private[0], &c, sizeof(c));
 139         if(n != sizeof(c)){
 140                 printk("update_thread : read failed, err = %d\n", -n);
 141                 goto fail;
 142         }
 143
 144         set_signals(flags);
 145         return;
 146  fail:
 147         /* Critical section start */
 148         if(write_sigio_pid != -1)
 149                 os_kill_process(write_sigio_pid, 1);
 150         write_sigio_pid = -1;
 151         close(sigio_private[0]);
 152         close(sigio_private[1]);
 153         close(write_sigio_fds[0]);
 154         close(write_sigio_fds[1]);
 155         /* Critical section end */
 156         set_signals(flags);
 157 }
 158
 159 int add_sigio_fd(int fd, int read)
 160 {
 161         int err = 0, i, n, events;
 162
 163         sigio_lock();
 164         for(i = 0; i < current_poll.used; i++){
 165                 if(current_poll.poll[i].fd == fd)
 166                         goto out;
 167         }
 168
 169         n = current_poll.used + 1;
 170         err = need_poll(n);
 171         if(err)
 172                 goto out;
 173
 174         for(i = 0; i < current_poll.used; i++)
 175                 next_poll.poll[i] = current_poll.poll[i];
 176
 177         if(read) events = POLLIN;
 178         else events = POLLOUT;
 179
 180         next_poll.poll[n - 1] = ((struct pollfd) { .fd          = fd,
 181                                                    .events      = events,
 182                                                    .revents     = 0 });
 183         update_thread();
 184  out:
 185         sigio_unlock();
 186         return(err);
 187 }
 188
 189 int ignore_sigio_fd(int fd)
 190 {
 191         struct pollfd *p;
 192         int err = 0, i, n = 0;
 193
 194         sigio_lock();
 195         for(i = 0; i < current_poll.used; i++){
 196                 if(current_poll.poll[i].fd == fd) break;
 197         }
 198         if(i == current_poll.used)
 199                 goto out;
 200
 201         err = need_poll(current_poll.used - 1);
 202         if(err)
 203                 goto out;
 204
 205         for(i = 0; i < current_poll.used; i++){
 206                 p = &current_poll.poll[i];
 207                 if(p->fd != fd) next_poll.poll[n++] = current_poll.poll[i];
 208         }
 209         if(n == i){
 210                 printk("ignore_sigio_fd : fd %d not found\n", fd);
 211                 err = -1;
 212                 goto out;
 213         }
 214
 215         update_thread();
 216  out:
 217         sigio_unlock();
 218         return(err);
 219 }
 220
 221 static struct pollfd *setup_initial_poll(int fd)
 222 {
 223         struct pollfd *p;
 224
 225         p = um_kmalloc(sizeof(struct pollfd));
 226         if (p == NULL) {
 227                 printk("setup_initial_poll : failed to allocate poll\n");
 228                 return NULL;
 229         }
 230         *p = ((struct pollfd) { .fd     = fd,
 231                                 .events         = POLLIN,
 232                                 .revents        = 0 });
 233         return p;
 234 }
 235
 236 void write_sigio_workaround(void)
 237 {
 238         unsigned long stack;
 239         struct pollfd *p;
 240         int err;
 241         int l_write_sigio_fds[2];
 242         int l_sigio_private[2];
 243         int l_write_sigio_pid;
 244
 245         /* We call this *tons* of times - and most ones we must just fail. */
 246         sigio_lock();
 247         l_write_sigio_pid = write_sigio_pid;
 248         sigio_unlock();
 249
 250         if (l_write_sigio_pid != -1)
 251                 return;
 252
 253         err = os_pipe(l_write_sigio_fds, 1, 1);
 254         if(err < 0){
 255                 printk("write_sigio_workaround - os_pipe 1 failed, "
 256                        "err = %d\n", -err);
 257                 return;
 258         }
 259         err = os_pipe(l_sigio_private, 1, 1);
 260         if(err < 0){
 261                 printk("write_sigio_workaround - os_pipe 2 failed, "
 262                        "err = %d\n", -err);
 263                 goto out_close1;
 264         }
 265
 266         p = setup_initial_poll(l_sigio_private[1]);
 267         if(!p)
 268                 goto out_close2;
 269
 270         sigio_lock();
 271
 272         /* Did we race? Don't try to optimize this, please, it's not so likely
 273          * to happen, and no more than once at the boot. */
 274         if(write_sigio_pid != -1)
 275                 goto out_free;
 276
 277         current_poll = ((struct pollfds) { .poll        = p,
 278                                            .used        = 1,
 279                                            .size        = 1 });
 280
 281         if (write_sigio_irq(l_write_sigio_fds[0]))
 282                 goto out_clear_poll;
 283
 284         memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds));
 285         memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private));
 286
 287         write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
 288                                             CLONE_FILES | CLONE_VM, &stack, 0);
 289
 290         if (write_sigio_pid < 0)
 291                 goto out_clear;
 292
 293         sigio_unlock();
 294         return;
 295
 296 out_clear:
 297         write_sigio_pid = -1;
 298         write_sigio_fds[0] = -1;
 299         write_sigio_fds[1] = -1;
 300         sigio_private[0] = -1;
 301         sigio_private[1] = -1;
 302 out_clear_poll:
 303         current_poll = ((struct pollfds) { .poll        = NULL,
 304                                            .size        = 0,
 305                                            .used        = 0 });
 306 out_free:
 307         sigio_unlock();
 308         kfree(p);
 309 out_close2:
 310         close(l_sigio_private[0]);
 311         close(l_sigio_private[1]);
 312 out_close1:
 313         close(l_write_sigio_fds[0]);
 314         close(l_write_sigio_fds[1]);
 315 }
 316
 317 void sigio_cleanup(void)
 318 {
 319         if(write_sigio_pid != -1){
 320                 os_kill_process(write_sigio_pid, 1);
 321                 write_sigio_pid = -1;
 322         }
 323 }