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, %lu\n", name, GetLastError ());
  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, %lu", m->name, winpid,
  47             GetLastError ());
  48   m->owner = winpid;
  49   _log (file, line, LOG_DEBUG, "Locked      mutex %s/%u (%u)",
  50         m->name, ++m->cnt, winpid);
  51 }
  52
  53 int
  54 mtx_owned (mtx *m, DWORD winpid)
  55 {
  56   return m->owner == winpid;
  57 }
  58
  59 void
  60 _mtx_assert (mtx *m, int what, DWORD winpid, const char *file, int line)
  61 {
  62   switch (what)
  63     {
  64       case MA_OWNED:
  65         if (!mtx_owned (m, winpid))
  66           _panic (file, line, "Mutex %s not owned", m->name);
  67         break;
  68       case MA_NOTOWNED:
  69         if (mtx_owned (m, winpid))
  70           _panic (file, line, "Mutex %s is owned", m->name);
  71         break;
  72       default:
  73         break;
  74     }
  75 }
  76
  77 void
  78 _mtx_unlock (mtx *m, const char *file, int line)
  79 {
  80   DWORD owner = m->owner;
  81   unsigned long cnt = m->cnt;
  82   m->owner = 0;
  83   /* Cautiously check if mtx_destroy has been called (shutdown).
  84      In that case, m->h is NULL. */
  85   if (m->h && !ReleaseSemaphore (m->h, 1, NULL))
  86     {
  87       /* Check if the semaphore was already on it's max value. */
  88       if (GetLastError () != ERROR_TOO_MANY_POSTS)
  89         _panic (file, line, "release of mutex %s failed, %lu", m->name,
  90                 GetLastError ());
  91     }
  92   _log (file, line, LOG_DEBUG, "Unlocked    mutex %s/%u (owner: %u)",
  93         m->name, cnt, owner);
  94 }
  95
  96 void
  97 mtx_destroy (mtx *m)
  98 {
  99   HANDLE tmp = m->h;
 100   m->h = NULL;
 101   if (tmp)
 102     CloseHandle (tmp);
 103 }
 104
 105 /*
 106  * Helper functions for msleep/wakeup.
 107  */
 108
 109 static int
 110 win_priority (int priority)
 111 {
 112   int p = (int)((priority) & PRIO_MASK) - PZERO;
 113   /* Generating a valid priority value is a bit tricky.  The only valid
 114      values on NT4 are -15, -2, -1, 0, 1, 2, 15. */
 115   switch (p)
 116     {
 117       case -15: case -14: case -13: case -12: case -11:
 118         return THREAD_PRIORITY_IDLE;
 119       case -10: case -9: case -8: case -7: case -6:
 120         return THREAD_PRIORITY_LOWEST;
 121       case -5: case -4: case -3: case -2: case -1:
 122         return THREAD_PRIORITY_BELOW_NORMAL;
 123       case 0:
 124         return THREAD_PRIORITY_NORMAL;
 125       case 1: case 2: case 3: case 4: case 5:
 126         return THREAD_PRIORITY_ABOVE_NORMAL;
 127       case 6: case 7: case 8: case 9: case 10:
 128         return THREAD_PRIORITY_HIGHEST;
 129       case 11: case 12: case 13: case 14: case 15:
 130         return THREAD_PRIORITY_TIME_CRITICAL;
 131     }
 132   return THREAD_PRIORITY_NORMAL;
 133 }
 134
 135 /*
 136  * Sets the thread priority, returns the old priority.
 137  */
 138 static int
 139 set_priority (int priority)
 140 {
 141   int old_prio = GetThreadPriority (GetCurrentThread ());
 142   if (!SetThreadPriority (GetCurrentThread (), win_priority (priority)))
 143     log (LOG_WARNING,
 144           "Warning: Setting thread priority to %d failed with error %lu\n",
 145           win_priority (priority), GetLastError ());
 146   return old_prio;
 147 }
 148
 149 /*
 150  * Original description from BSD code:
 151  *
 152  * General sleep call.  Suspends the current process until a wakeup is
 153  * performed on the specified identifier.  The process will then be made
 154  * runnable with the specified priority.  Sleeps at most timo/hz seconds
 155  * (0 means no timeout).  If pri includes PCATCH flag, signals are checked
 156  * before and after sleeping, else signals are not checked.  Returns 0 if
 157  * awakened, EWOULDBLOCK if the timeout expires.  If PCATCH is set and a
 158  * signal needs to be delivered, ERESTART is returned if the current system
 159  * call should be restarted if possible, and EINTR is returned if the system
 160  * call should be interrupted by the signal (return EINTR).
 161  *
 162  * The mutex argument is exited before the caller is suspended, and
 163  * entered before msleep returns.  If priority includes the PDROP
 164  * flag the mutex is not entered before returning.
 165  */
 166 static HANDLE msleep_glob_evt;
 167
 168 class msleep_sync_array
 169 {
 170   enum msleep_action {
 171     MSLEEP_ENTER = 0,
 172     MSLEEP_LEAVE,
 173     MSLEEP_WAKEUP
 174   };
 175
 176   CRITICAL_SECTION cs;
 177   long cnt;
 178   long max_cnt;
 179   struct msleep_record {
 180     void *ident;
 181     HANDLE wakeup_evt;
 182     LONG threads;
 183   } *a;
 184
 185   int find_ident (void *ident, msleep_action action)
 186   {
 187     int i;
 188     for (i = 0; i < cnt; ++i)
 189       if (a[i].ident == ident)
 190         return i;
 191     if (i >= max_cnt)
 192       panic ("ident %x not found and run out of slots.", ident);
 193     if (i >= cnt && action == MSLEEP_LEAVE)
 194       panic ("ident %x not found (%d).", ident, action);
 195     return i;
 196   }
 197
 198   HANDLE first_entry (int i, void *ident)
 199   {
 200     debug ("New ident %x, index %d", ident, i);
 201     a[i].ident = ident;
 202     a[i].wakeup_evt = CreateEvent (NULL, TRUE, FALSE, NULL);
 203     if (!a[i].wakeup_evt)
 204       panic ("CreateEvent failed: %lu", GetLastError ());
 205     debug ("i = %d, CreateEvent: %x", i, a[i].wakeup_evt);
 206     a[i].threads = 1;
 207     ++cnt;
 208     return a[i].wakeup_evt;
 209   }
 210
 211   HANDLE next_entry (int i)
 212   {
 213     if (a[i].ident && WaitForSingleObject (a[i].wakeup_evt, 0) != WAIT_OBJECT_0)
 214       {
 215         ++a[i].threads;
 216         return a[i].wakeup_evt;
 217       }
 218     return NULL;
 219   }
 220
 221 public:
 222
 223   msleep_sync_array (int count) : cnt (0), max_cnt (count)
 224   {
 225     InitializeCriticalSection (&cs);
 226     if (!(a = new msleep_record[count]))
 227       panic ("Allocating msleep records failed: %d", errno);
 228   }
 229
 230   HANDLE enter (void *ident)
 231   {
 232     HANDLE evt = NULL;
 233     while (!evt)
 234       {
 235         EnterCriticalSection (&cs);
 236         int i = find_ident (ident, MSLEEP_ENTER);
 237         if (i >= cnt)
 238           evt = first_entry (i, ident);
 239         else if (!(evt = next_entry (i)))
 240           {
 241             /* wakeup has been called, so sleep to wait until all
 242                formerly waiting threads have left and retry. */
 243             LeaveCriticalSection (&cs);
 244             Sleep (1L);
 245           }
 246       }
 247     LeaveCriticalSection (&cs);
 248     return evt;
 249   }
 250
 251   void leave (void *ident)
 252   {
 253     EnterCriticalSection (&cs);
 254     int i = find_ident (ident, MSLEEP_LEAVE);
 255     if (--a[i].threads == 0)
 256       {
 257         debug ("i = %d, CloseEvent: %x", i, a[i].wakeup_evt);
 258         CloseHandle (a[i].wakeup_evt);
 259         a[i].ident = NULL;
 260         --cnt;
 261         if (i < cnt)
 262           a[i] = a[cnt];
 263       }
 264     LeaveCriticalSection (&cs);
 265   }
 266
 267   void wakeup (void *ident)
 268   {
 269     EnterCriticalSection (&cs);
 270     int i = find_ident (ident, MSLEEP_WAKEUP);
 271     if (i < cnt && a[i].ident)
 272       SetEvent (a[i].wakeup_evt);
 273     LeaveCriticalSection (&cs);
 274   }
 275 };
 276
 277 static msleep_sync_array *msleep_sync;
 278
 279 void
 280 msleep_init (void)
 281 {
 282   extern struct msginfo msginfo;
 283   extern struct seminfo seminfo;
 284
 285   msleep_glob_evt = CreateEvent (NULL, TRUE, FALSE, NULL);
 286   if (!msleep_glob_evt)
 287     panic ("CreateEvent in msleep_init failed: %lu", GetLastError ());
 288   long msgmni = support_msgqueues ? msginfo.msgmni : 0;
 289   long semmni = support_semaphores ? seminfo.semmni : 0;
 290   TUNABLE_INT_FETCH ("kern.ipc.msgmni", &msgmni);
 291   TUNABLE_INT_FETCH ("kern.ipc.semmni", &semmni);
 292   debug ("Try allocating msgmni (%d) + semmni (%d) msleep records",
 293          msgmni, semmni);
 294   msleep_sync = new msleep_sync_array (msgmni + semmni);
 295   if (!msleep_sync)
 296     panic ("Allocating msleep records in msleep_init failed: %d", errno);
 297 }
 298
 299 int
 300 _msleep (void *ident, struct mtx *mtx, int priority,
 301         const char *wmesg, int timo, struct thread *td)
 302 {
 303   int ret = -1;
 304
 305   HANDLE evt = msleep_sync->enter (ident);
 306
 307   if (mtx)
 308     mtx_unlock (mtx);
 309   int old_priority = set_priority (priority);
 310   HANDLE obj[4] =
 311     {
 312       evt,
 313       msleep_glob_evt,
 314       td->client->handle (),
 315       td->client->signal_arrived ()
 316     };
 317   /* PCATCH handling.  If PCATCH is given and signal_arrived is a valid
 318      handle, then it's used in the WaitFor call and EINTR is returned. */
 319   int obj_cnt = 3;
 320   if ((priority & PCATCH)
 321       && td->client->signal_arrived () != INVALID_HANDLE_VALUE)
 322     obj_cnt = 4;
 323   switch (WaitForMultipleObjects (obj_cnt, obj, FALSE, timo ?: INFINITE))
 324     {
 325       case WAIT_OBJECT_0:       /* wakeup() has been called. */
 326         ret = 0;
 327         debug ("msleep wakeup called for %d", td->td_proc->winpid);
 328         break;
 329       case WAIT_OBJECT_0 + 1:   /* Shutdown event (triggered by wakeup_all). */
 330         priority |= PDROP;
 331         /*FALLTHRU*/
 332       case WAIT_OBJECT_0 + 2:   /* The dependent process has exited. */
 333         debug ("msleep process exit or shutdown for %d", td->td_proc->winpid);
 334         ret = EIDRM;
 335         break;
 336       case WAIT_OBJECT_0 + 3:   /* Signal for calling process arrived. */
 337         debug ("msleep process got signal for %d", td->td_proc->winpid);
 338         ret = EINTR;
 339         break;
 340       case WAIT_TIMEOUT:
 341         ret = EWOULDBLOCK;
 342         break;
 343       default:
 344         /* There's a chance that a process has been terminated before
 345            WaitForMultipleObjects has been called.  In this case the handles
 346            might be invalid.  The error code returned is ERROR_INVALID_HANDLE.
 347            Since we can trust the values of these handles otherwise, we
 348            treat an ERROR_INVALID_HANDLE as a normal process termination and
 349            hope for the best. */
 350         if (GetLastError () != ERROR_INVALID_HANDLE)
 351           panic ("wait in msleep (%s) failed, %lu", wmesg, GetLastError ());
 352         debug ("wait in msleep (%s) failed for %d, %lu", wmesg,
 353                td->td_proc->winpid, GetLastError ());
 354         ret = EIDRM;
 355         break;
 356     }
 357
 358   msleep_sync->leave (ident);
 359
 360   set_priority (old_priority);
 361
 362   if (mtx && !(priority & PDROP))
 363     mtx_lock (mtx);
 364   return ret;
 365 }
 366
 367 /*
 368  * Make all threads sleeping on the specified identifier runnable.
 369  */
 370 int
 371 wakeup (void *ident)
 372 {
 373   msleep_sync->wakeup (ident);
 374   return 0;
 375 }
 376
 377 /*
 378  * Wakeup all sleeping threads.  Only called in the context of cygserver
 379  * shutdown.
 380  */
 381 void
 382 wakeup_all (void)
 383 {
 384   SetEvent (msleep_glob_evt);
 385 }
 386 #endif /* __OUTSIDE_CYGWIN__ */