include/cancel.h

   1 /*
   2  * Copyright (C) 2000-2011 Erik Andersen <andersen@uclibc.org>
   3  *
   4  * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
   5  */
   6
   7 #ifndef _CANCEL_H
   8 #define _CANCEL_H
   9
  10 /*
  11  * Usage of this header:
  12  * 1. define a static or hidden function __NC(NAME) - expands to __NAME_nocancel
  13  * 2. if it is hidden, add the prototype to the appropiate header where NAME has
  14  * it's prototype (guarded by _LIBC)
  15  * 3. add a CANCELLABLE_SYSCALL(...) line at the end, this will create the function
  16  * NAME (as weak) with enabled cancellation for NPTL, for
  17  * LT it will also create a strong_alias to __libc_NAME to be used in libpthread
  18  * 4. if you need libc_hidden_(weak|def) line, use instead lt_libc_hidden, this will
  19  * take care of the correct type, weak or strong depending on the THREADS type
  20  * 5. If the implementation can't be done using CANCELLABLE_SYSCALL (like for fcntl)
  21  * you need to manually add lt_strong_alias() line too, to optionally create the
  22  * __libc_NAME alias
  23  * 6. if functions are needed to implement __NC(NAME), that themselves are cancellable,
  24  * decide how the cancellation should be solved, two variants are possible:
  25  *  a. use the other function as __NC(FUNC), this way you access the non-cancellable
  26  *  variant and provide by CANCELLABLE_SYSCALL(...) the dedicated cancellation for NAME.
  27  *  be aware, that for this case __NC(FUNC) has to be hidden (not static)
  28  *  b. use the other function with it's name (FUNC) and add LIBC_CANCEL_HANDLED(); at
  29  *  the end of file with a comment telling us which function took care of the cancellation
  30  * Note: LIBC_CANCEL_HANDLED() is noop on uClibc, glibc uses it only for tests, we use
  31  * it only for "documentation".
  32  *
  33  * For now the use of this file is limited to libc, will expand later to support libpthread
  34  * and librt as well.
  35  */
  36
  37 #include <features.h>
  38
  39 #define __NC(name) _NC(name)
  40 #define _NC(name) __##name##_nocancel
  41
  42 #define __NC_OLD(name) _NC_OLD(name)
  43 #define _NC_OLD(name) __libc_##name
  44
  45 #define __NC_PROTO(name) extern __typeof(name) __NC(name) attribute_hidden;
  46 #define __NC_OLD_PROTO(name) extern __typeof(name) __NC_OLD(name);
  47
  48 #if defined __UCLIBC_HAS_THREADS__ && !defined __UCLIBC_HAS_LINUXTHREADS__
  49 # define __NEW_THREADS 1
  50 #else
  51 # define SINGLE_THREAD_P 1
  52 #endif
  53
  54 #ifdef __NEW_THREADS
  55 # include <sysdep-cancel.h>
  56
  57 # define CANCELLABLE_SYSCALL(res_type, name, param_list, params)        \
  58 res_type weak_function name param_list                                  \
  59 {                                                                       \
  60         int oldtype;                                                    \
  61         res_type result;                                                \
  62         if (SINGLE_THREAD_P)                                            \
  63                 return __NC(name) params;                               \
  64         oldtype = LIBC_CANCEL_ASYNC();                                  \
  65         result = __NC(name) params;                                     \
  66         LIBC_CANCEL_RESET(oldtype);                                     \
  67         return result;                                                  \
  68 }
  69
  70 # define lt_strong_alias(name)
  71 # define lt_libc_hidden(name) libc_hidden_def(name)
  72
  73 #elif defined __UCLIBC_HAS_LINUXTHREADS__
  74
  75 # define CANCELLABLE_SYSCALL(res_type, name, param_list, params)        \
  76 weak_alias(__NC(name),name)                                             \
  77 lt_strong_alias(name)
  78
  79 # define lt_strong_alias(name)                                          \
  80 __NC_OLD_PROTO(name)                                                    \
  81 strong_alias(name,__NC_OLD(name))
  82 # define lt_libc_hidden(name) libc_hidden_weak(name)
  83
  84 #else
  85
  86 # define CANCELLABLE_SYSCALL(res_type, name, param_list, params)        \
  87 strong_alias(__NC(name),name)
  88
  89 # define lt_strong_alias(name)
  90 # define lt_libc_hidden(name) libc_hidden_def(name)
  91
  92 #endif
  93
  94 /* disable it, useless, glibc uses it only for tests */
  95 # undef LIBC_CANCEL_HANDLED
  96 # define LIBC_CANCEL_HANDLED()
  97
  98 #endif