libgcc/config/i386/gthr-win32-thread.c

   1 /* Implementation of threads compatibility routines for libgcc2.  */
   2
   3 /* Copyright (C) 1999-2024 Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 3, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 Under Section 7 of GPL version 3, you are granted additional
  18 permissions described in the GCC Runtime Library Exception, version
  19 3.1, as published by the Free Software Foundation.
  20
  21 You should have received a copy of the GNU General Public License and
  22 a copy of the GCC Runtime Library Exception along with this program;
  23 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24 <http://www.gnu.org/licenses/>.  */
  25
  26 /* This module is separate from the rest of the implementation because only
  27    one copy of it ought to be linked.  */
  28
  29 /* The implementation strategy for the c++0x thread support is as follows.
  30
  31    A GNU thread is represented by a Win32 HANDLE that is obtained when the
  32    Win32 thread is created, except of course for the initial thread.  This
  33    Win32 HANDLE is stored in a descriptor keyed from TLS memory for every
  34    thread, so the self routine can return it instead of having to duplicate
  35    the pseudo-handle returned by GetCurrentThread each time it is invoked.
  36    For the initial thread, this Win32 HANDLE is created during the first
  37    call to the self routine using the aforementioned technique.
  38
  39    Note that the equal routine compares the identifier of threads instead
  40    of their Win32 HANDLE, which will give the correct positive answer even
  41    in the case where distinct Win32 HANDLEs have been created for the same
  42    thread by multiple instances of libgcc included in the link.  */
  43
  44 #include "gthr-win32.h"
  45
  46 /* The thread descriptor keyed from TLS memory.  */
  47 struct __gthr_win32_thr_desc
  48 {
  49   void *(*func) (void*);
  50   void *args;
  51   HANDLE h;
  52 };
  53
  54 /* The TLS key used by one instance of the library.  */
  55 static __gthread_key_t __gthr_win32_tls = TLS_OUT_OF_INDEXES;
  56
  57 /* The initialization device for the TLS key.  */
  58 static __gthread_once_t __gthr_win32_tls_once = __GTHREAD_ONCE_INIT;
  59
  60 /* Initialize the TLS key.  */
  61
  62 static void
  63 __gthr_win32_tls_init (void)
  64 {
  65   if (__gthread_key_create (&__gthr_win32_tls, free))
  66     abort ();
  67 }
  68
  69 /* Wrapper routine around thread functions.  */
  70
  71 static DWORD
  72 __gthr_win32_thread_wrapper (void *args)
  73 {
  74   struct __gthr_win32_thr_desc *td = (struct __gthr_win32_thr_desc *) args;
  75
  76   __gthread_setspecific (__gthr_win32_tls, td);
  77
  78   DWORD exit_code = (DWORD) (ULONG_PTR) (*td->func) (td->args);
  79
  80   ExitThread (exit_code);
  81   return exit_code;
  82 }
  83
  84 /* Implement the __gthread_create routine.  */
  85
  86 int
  87 __gthr_win32_create (__gthread_t *thr, void *(*func) (void*), void *args)
  88 {
  89   struct __gthr_win32_thr_desc *td;
  90
  91   __gthread_once (&__gthr_win32_tls_once, __gthr_win32_tls_init);
  92
  93   td = malloc (sizeof (struct __gthr_win32_thr_desc));
  94   td->func = func;
  95   td->args = args;
  96   td->h = CreateThread (NULL, 0,
  97                         (LPTHREAD_START_ROUTINE) __gthr_win32_thread_wrapper,
  98                         (LPVOID) td, CREATE_SUSPENDED, NULL);
  99   if (td->h)
 100     {
 101       ResumeThread (td->h);
 102       *thr = (__gthread_t) td->h;
 103       return 0;
 104     }
 105   else
 106     {
 107       free (td);
 108       return (int) GetLastError ();
 109     }
 110 }
 111
 112 /* Implement the __gthread_join routine.  */
 113
 114 int
 115 __gthr_win32_join (__gthread_t thr, void **value_ptr)
 116 {
 117   int status = 0;
 118
 119   if (GetThreadId ((HANDLE) thr) == GetCurrentThreadId ())
 120     return 1;
 121
 122   if (WaitForSingleObject ((HANDLE) thr, INFINITE) == WAIT_OBJECT_0)
 123     {
 124       if (value_ptr)
 125         {
 126           DWORD exit_code;
 127           if (GetExitCodeThread ((HANDLE) thr, &exit_code))
 128             *value_ptr = (void *) (ULONG_PTR) exit_code;
 129           else
 130             status = (int) GetLastError ();
 131         }
 132     }
 133   else
 134     status = (int) GetLastError ();
 135
 136   CloseHandle ((HANDLE) thr);
 137   return status;
 138 }
 139
 140 /* Implement the __gthread_self routine.  */
 141
 142 __gthread_t
 143 __gthr_win32_self (void)
 144 {
 145   struct __gthr_win32_thr_desc *td;
 146
 147   __gthread_once (&__gthr_win32_tls_once, __gthr_win32_tls_init);
 148
 149   if (!(td = __gthread_getspecific (__gthr_win32_tls)))
 150     {
 151       HANDLE proc = GetCurrentProcess ();
 152       td = malloc (sizeof (struct __gthr_win32_thr_desc));
 153       td->func = NULL;
 154       td->args = NULL;
 155       if (!DuplicateHandle (proc, GetCurrentThread(), proc, &td->h, 0, FALSE,
 156                             DUPLICATE_SAME_ACCESS))
 157         abort ();
 158       __gthread_setspecific (__gthr_win32_tls, td);
 159     }
 160
 161   return td->h;
 162 }