winsup/cygserver/bsd_mutex.cc

   1 /* bsd_mutex.cc
   2
   3    Copyright 2003, 2004, 2005, 2007 Red Hat Inc.
   4
   5 This file is part of Cygwin.
   6
   7 This software is a copyrighted work licensed under the terms of the
   8 Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
   9 details. */
  10 #ifdef __OUTSIDE_CYGWIN__
  11 #include "woutsup.h"
  12 #include <errno.h>
  13 #define _KERNEL 1
  14 #define __BSD_VISIBLE 1
  15 #include <sys/smallprint.h>
  16 #include <limits.h>
  17 #include <stdlib.h>
  18 #include <sys/msg.h>
  19 #include <sys/sem.h>
  20
  21 #include "process.h"
  22 #include "cygserver_ipc.h"
  23
  24 /* A BSD kernel global mutex. */
  25 struct mtx Giant;
  26
  27 void
  28 mtx_init (mtx *m, const char *name, const void *, int)
  29 {
  30   m->name = name;
  31   m->owner = 0;
  32   m->cnt = 0;
  33   /* Can't use Windows Mutexes here since Windows Mutexes are only
  34      unlockable by the lock owner. */
  35   m->h = CreateSemaphore (NULL, 1, 1, NULL);
  36   if (!m->h)
  37     panic ("couldn't allocate %s mutex, %E\n", name);
  38 }
  39
  40 void
  41 _mtx_lock (mtx *m, DWORD winpid, const char *file, int line)
  42 {
  43   _log (file, line, LOG_DEBUG, "Try locking mutex %s (%u) (hold: %u)",
  44         m->name, winpid, m->owner);
  45   if (WaitForSingleObject (m->h, INFINITE) != WAIT_OBJECT_0)
  46     _panic (file, line, "wait for %s in %d failed, %E", m->name, winpid);
  47   m->owner = winpid;
  48   _log (file, line, LOG_DEBUG, "Locked      mutex %s/%u (%u)",
  49         m->name, ++m->cnt, winpid);
  50 }
  51
  52 int
  53 mtx_owned (mtx *m, DWORD winpid)
  54 {
  55   return m->owner == winpid;
  56 }
  57
  58 void
  59 _mtx_assert (mtx *m, int what, DWORD winpid, const char *file, int line)
  60 {
  61   switch (what)
  62     {
  63       case MA_OWNED:
  64         if (!mtx_owned (m, winpid))
  65           _panic (file, line, "Mutex %s not owned", m->name);
  66         break;
  67       case MA_NOTOWNED:
  68         if (mtx_owned (m, winpid))
  69           _panic (file, line, "Mutex %s is owned", m->name);
  70         break;
  71       default:
  72         break;
  73     }
  74 }
  75
  76 void
  77 _mtx_unlock (mtx *m, const char *file, int line)
  78 {
  79   DWORD owner = m->owner;
  80   unsigned long cnt = m->cnt;
  81   m->owner = 0;
  82   /* Cautiously check if mtx_destroy has been called (shutdown).
  83      In that case, m->h is NULL. */
  84   if (m->h && !ReleaseSemaphore (m->h, 1, NULL))
  85     {
  86       /* Check if the semaphore was already on it's max value. */
  87       if (GetLastError () != ERROR_TOO_MANY_POSTS)
  88         _panic (file, line, "release of mutex %s failed, %E", m->name);
  89     }
  90   _log (file, line, LOG_DEBUG, "Unlocked    mutex %s/%u (owner: %u)",
  91         m->name, cnt, owner);
  92 }
  93
  94 void
  95 mtx_destroy (mtx *m)
  96 {
  97   HANDLE tmp = m->h;
  98   m->h = NULL;
  99   if (tmp)
 100     CloseHandle (tmp);
 101 }
 102
 103 /*
 104  * Helper functions for msleep/wakeup.
 105  */
 106
 107 static int
 108 win_priority (int priority)
 109 {
 110   int p = (int)((priority) & PRIO_MASK) - PZERO;
 111   /* Generating a valid priority value is a bit tricky.  The only valid
 112      values on NT4 are -15, -2, -1, 0, 1, 2, 15. */
 113   switch (p)
 114     {
 115       case -15: case -14: case -13: case -12: case -11:
 116         return THREAD_PRIORITY_IDLE;
 117       case -10: case -9: case -8: case -7: case -6:
 118         return THREAD_PRIORITY_LOWEST;
 119       case -5: case -4: case -3: case -2: case -1:
 120         return THREAD_PRIORITY_BELOW_NORMAL;
 121       case 0:
 122         return THREAD_PRIORITY_NORMAL;
 123       case 1: case 2: case 3: case 4: case 5:
 124         return THREAD_PRIORITY_ABOVE_NORMAL;
 125       case 6: case 7: case 8: case 9: case 10:
 126         return THREAD_PRIORITY_HIGHEST;
 127       case 11: case 12: case 13: case 14: case 15:
 128         return THREAD_PRIORITY_TIME_CRITICAL;
 129     }
 130   return THREAD_PRIORITY_NORMAL;
 131 }
 132
 133 /*
 134  * Sets the thread priority, returns the old priority.
 135  */
 136 static int
 137 set_priority (int priority)
 138 {
 139   int old_prio = GetThreadPriority (GetCurrentThread ());
 140   if (!SetThreadPriority (GetCurrentThread (), win_priority (priority)))
 141     log (LOG_WARNING,
 142           "Warning: Setting thread priority to %d failed with error %lu\n",
 143           win_priority (priority), GetLastError ());
 144   return old_prio;
 145 }
 146
 147 /*
 148  * Original description from BSD code:
 149  *
 150  * General sleep call.  Suspends the current process until a wakeup is
 151  * performed on the specified identifier.  The process will then be made
 152  * runnable with the specified priority.  Sleeps at most timo/hz seconds
 153  * (0 means no timeout).  If pri includes PCATCH flag, signals are checked
 154  * before and after sleeping, else signals are not checked.  Returns 0 if
 155  * awakened, EWOULDBLOCK if the timeout expires.  If PCATCH is set and a
 156  * signal needs to be delivered, ERESTART is returned if the current system
 157  * call should be restarted if possible, and EINTR is returned if the system
 158  * call should be interrupted by the signal (return EINTR).
 159  *
 160  * The mutex argument is exited before the caller is suspended, and
 161  * entered before msleep returns.  If priority includes the PDROP
 162  * flag the mutex is not entered before returning.
 163  */
 164 static HANDLE msleep_glob_evt;
 165
 166 class msleep_sync_array
 167 {
 168   enum msleep_action {
 169     MSLEEP_ENTER = 0,
 170     MSLEEP_LEAVE,
 171     MSLEEP_WAKEUP
 172   };
 173
 174   CRITICAL_SECTION cs;
 175   long cnt;
 176   long max_cnt;
 177   struct msleep_record {
 178     void *ident;
 179     HANDLE wakeup_evt;
 180     LONG threads;
 181   } *a;
 182
 183   int find_ident (void *ident, msleep_action action)
 184   {
 185     int i;
 186     for (i = 0; i < cnt; ++i)
 187       if (a[i].ident == ident)
 188         return i;
 189     if (i >= max_cnt)
 190       panic ("ident %x not found and run out of slots.", ident);
 191     if (i >= cnt && action == MSLEEP_LEAVE)
 192       panic ("ident %x not found (%d).", ident, action);
 193     return i;
 194   }
 195
 196   HANDLE first_entry (int i, void *ident)
 197   {
 198     debug ("New ident %x, index %d", ident, i);
 199     a[i].ident = ident;
 200     a[i].wakeup_evt = CreateEvent (NULL, TRUE, FALSE, NULL);
 201     if (!a[i].wakeup_evt)
 202       panic ("CreateEvent failed: %E");
 203     debug ("i = %d, CreateEvent: %x", i, a[i].wakeup_evt);
 204     a[i].threads = 1;
 205     ++cnt;
 206     return a[i].wakeup_evt;
 207   }
 208
 209   HANDLE next_entry (int i)
 210   {
 211     if (a[i].ident && WaitForSingleObject (a[i].wakeup_evt, 0) != WAIT_OBJECT_0)
 212       {
 213         ++a[i].threads;
 214         return a[i].wakeup_evt;
 215       }
 216     return NULL;
 217   }
 218
 219 public:
 220
 221   msleep_sync_array (int count) : cnt (0), max_cnt (count)
 222   {
 223     InitializeCriticalSection (&cs);
 224     if (!(a = new msleep_record[count]))
 225       panic ("Allocating msleep records failed: %d", errno);
 226   }
 227
 228   HANDLE enter (void *ident)
 229   {
 230     HANDLE evt = NULL;
 231     while (!evt)
 232       {
 233         EnterCriticalSection (&cs);
 234         int i = find_ident (ident, MSLEEP_ENTER);
 235         if (i >= cnt)
 236           evt = first_entry (i, ident);
 237         else if (!(evt = next_entry (i)))
 238           {
 239             /* wakeup has been called, so sleep to wait until all
 240                formerly waiting threads have left and retry. */
 241             LeaveCriticalSection (&cs);
 242             Sleep (1L);
 243           }
 244       }
 245     LeaveCriticalSection (&cs);
 246     return evt;
 247   }
 248
 249   void leave (void *ident)
 250   {
 251     EnterCriticalSection (&cs);
 252     int i = find_ident (ident, MSLEEP_LEAVE);
 253     if (--a[i].threads == 0)
 254       {
 255         debug ("i = %d, CloseEvent: %x", i, a[i].wakeup_evt);
 256         CloseHandle (a[i].wakeup_evt);
 257         a[i].ident = NULL;
 258         --cnt;
 259         if (i < cnt)
 260           a[i] = a[cnt];
 261       }
 262     LeaveCriticalSection (&cs);
 263   }
 264
 265   void wakeup (void *ident)
 266   {
 267     EnterCriticalSection (&cs);
 268     int i = find_ident (ident, MSLEEP_WAKEUP);
 269     if (i < cnt && a[i].ident)
 270       SetEvent (a[i].wakeup_evt);
 271     LeaveCriticalSection (&cs);
 272   }
 273 };
 274
 275 static msleep_sync_array *msleep_sync;
 276
 277 void
 278 msleep_init (void)
 279 {
 280   extern struct msginfo msginfo;
 281   extern struct seminfo seminfo;
 282
 283   msleep_glob_evt = CreateEvent (NULL, TRUE, FALSE, NULL);
 284   if (!msleep_glob_evt)
 285     panic ("CreateEvent in msleep_init failed: %E");
 286   long msgmni = support_msgqueues ? msginfo.msgmni : 0;
 287   long semmni = support_semaphores ? seminfo.semmni : 0;
 288   TUNABLE_INT_FETCH ("kern.ipc.msgmni", &msgmni);
 289   TUNABLE_INT_FETCH ("kern.ipc.semmni", &semmni);
 290   debug ("Try allocating msgmni (%d) + semmni (%d) msleep records",
 291          msgmni, semmni);
 292   msleep_sync = new msleep_sync_array (msgmni + semmni);
 293   if (!msleep_sync)
 294     panic ("Allocating msleep records in msleep_init failed: %d", errno);
 295 }
 296
 297 int
 298 _msleep (void *ident, struct mtx *mtx, int priority,
 299         const char *wmesg, int timo, struct thread *td)
 300 {
 301   int ret = -1;
 302
 303   HANDLE evt = msleep_sync->enter (ident);
 304
 305   if (mtx)
 306     mtx_unlock (mtx);
 307   int old_priority = set_priority (priority);
 308   HANDLE obj[4] =
 309     {
 310       evt,
 311       msleep_glob_evt,
 312       td->client->handle (),
 313       td->client->signal_arrived ()
 314     };
 315   /* PCATCH handling.  If PCATCH is given and signal_arrived is a valid
 316      handle, then it's used in the WaitFor call and EINTR is returned. */
 317   int obj_cnt = 3;
 318   if ((priority & PCATCH)
 319       && td->client->signal_arrived () != INVALID_HANDLE_VALUE)
 320     obj_cnt = 4;
 321   switch (WaitForMultipleObjects (obj_cnt, obj, FALSE, timo ?: INFINITE))
 322     {
 323       case WAIT_OBJECT_0:       /* wakeup() has been called. */
 324         ret = 0;
 325         debug ("msleep wakeup called for %d", td->td_proc->winpid);
 326         break;
 327       case WAIT_OBJECT_0 + 1:   /* Shutdown event (triggered by wakeup_all). */
 328         priority |= PDROP;
 329         /*FALLTHRU*/
 330       case WAIT_OBJECT_0 + 2:   /* The dependent process has exited. */
 331         debug ("msleep process exit or shutdown for %d", td->td_proc->winpid);
 332         ret = EIDRM;
 333         break;
 334       case WAIT_OBJECT_0 + 3:   /* Signal for calling process arrived. */
 335         debug ("msleep process got signal for %d", td->td_proc->winpid);
 336         ret = EINTR;
 337         break;
 338       case WAIT_TIMEOUT:
 339         ret = EWOULDBLOCK;
 340         break;
 341       default:
 342         /* There's a chance that a process has been terminated before
 343            WaitForMultipleObjects has been called.  In this case the handles
 344            might be invalid.  The error code returned is ERROR_INVALID_HANDLE.
 345            Since we can trust the values of these handles otherwise, we
 346            treat an ERROR_INVALID_HANDLE as a normal process termination and
 347            hope for the best. */
 348         if (GetLastError () != ERROR_INVALID_HANDLE)
 349           panic ("wait in msleep (%s) failed, %E", wmesg);
 350         debug ("wait in msleep (%s) failed for %d, %E", wmesg,
 351                                                         td->td_proc->winpid);
 352         ret = EIDRM;
 353         break;
 354     }
 355
 356   msleep_sync->leave (ident);
 357
 358   set_priority (old_priority);
 359
 360   if (mtx && !(priority & PDROP))
 361     mtx_lock (mtx);
 362   return ret;
 363 }
 364
 365 /*
 366  * Make all threads sleeping on the specified identifier runnable.
 367  */
 368 int
 369 wakeup (void *ident)
 370 {
 371   msleep_sync->wakeup (ident);
 372   return 0;
 373 }
 374
 375 /*
 376  * Wakeup all sleeping threads.  Only called in the context of cygserver
 377  * shutdown.
 378  */
 379 void
 380 wakeup_all (void)
 381 {
 382   SetEvent (msleep_glob_evt);
 383 }
 384 #endif /* __OUTSIDE_CYGWIN__ */