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gthr-win32-thread.c revision 1.1 
      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 }
    163