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 99