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/* * Copyright (C) 2000-2011 Erik Andersen <andersen@uclibc.org> * * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball. */ #ifndef _CANCEL_H #define _CANCEL_H /* * Usage of this header: * 1. define a static or hidden function __NC(NAME) - expands to __NAME_nocancel * 2. if it is hidden, add the prototype to the appropiate header where NAME has * it's prototype (guarded by _LIBC) * 3. add a CANCELLABLE_SYSCALL(...) line at the end, this will create the function * NAME (as weak) with enabled cancellation for NPTL, for * LT it will also create a strong_alias to __libc_NAME to be used in libpthread * 4. if you need libc_hidden_(weak|def) line, use instead lt_libc_hidden, this will * take care of the correct type, weak or strong depending on the THREADS type * 5. If the implementation can't be done using CANCELLABLE_SYSCALL (like for fcntl) * you need to manually add lt_strong_alias() line too, to optionally create the * __libc_NAME alias * 6. if functions are needed to implement __NC(NAME), that themselves are cancellable, * decide how the cancellation should be solved, two variants are possible: * a. use the other function as __NC(FUNC), this way you access the non-cancellable * variant and provide by CANCELLABLE_SYSCALL(...) the dedicated cancellation for NAME. * be aware, that for this case __NC(FUNC) has to be hidden (not static) * b. use the other function with it's name (FUNC) and add LIBC_CANCEL_HANDLED(); at * the end of file with a comment telling us which function took care of the cancellation * Note: LIBC_CANCEL_HANDLED() is noop on uClibc, glibc uses it only for tests, we use * it only for "documentation". * * For now the use of this file is limited to libc, will expand later to support libpthread * and librt as well. */ #include <features.h> #define __NC(name) _NC(name) #define _NC(name) __##name##_nocancel #define __NC_OLD(name) _NC_OLD(name) #define _NC_OLD(name) __libc_##name #define __NC_PROTO(name) extern __typeof(name) __NC(name) attribute_hidden; #define __NC_OLD_PROTO(name) extern __typeof(name) __NC_OLD(name); #if defined __UCLIBC_HAS_THREADS__ && !defined __UCLIBC_HAS_LINUXTHREADS__ # define __NEW_THREADS 1 #else # define SINGLE_THREAD_P 1 #endif #ifdef __NEW_THREADS # include <sysdep-cancel.h> # define CANCELLABLE_SYSCALL(res_type, name, param_list, params) \ res_type weak_function name param_list \ { \ int oldtype; \ res_type result; \ if (SINGLE_THREAD_P) \ return __NC(name) params; \ oldtype = LIBC_CANCEL_ASYNC(); \ result = __NC(name) params; \ LIBC_CANCEL_RESET(oldtype); \ return result; \ } # define lt_strong_alias(name) # define lt_libc_hidden(name) libc_hidden_def(name) #elif defined __UCLIBC_HAS_LINUXTHREADS__ # define CANCELLABLE_SYSCALL(res_type, name, param_list, params) \ weak_alias(__NC(name),name) \ lt_strong_alias(name) # define lt_strong_alias(name) \ __NC_OLD_PROTO(name) \ strong_alias(name,__NC_OLD(name)) # define lt_libc_hidden(name) libc_hidden_weak(name) #else # define CANCELLABLE_SYSCALL(res_type, name, param_list, params) \ strong_alias(__NC(name),name) # define lt_strong_alias(name) # define lt_libc_hidden(name) libc_hidden_def(name) #endif /* disable it, useless, glibc uses it only for tests */ # undef LIBC_CANCEL_HANDLED # define LIBC_CANCEL_HANDLED() #endif |