1// Copyright 2014 The Android Open Source Project 2// 3// This software is licensed under the terms of the GNU General Public 4// License version 2, as published by the Free Software Foundation, and 5// may be copied, distributed, and modified under those terms. 6// 7// This program is distributed in the hope that it will be useful, 8// but WITHOUT ANY WARRANTY; without even the implied warranty of 9// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 10// GNU General Public License for more details. 11#ifndef ANDROID_UTILS_EINTR_WRAPPER_H 12#define ANDROID_UTILS_EINTR_WRAPPER_H 13 14#include <errno.h> 15 16#include "android/utils/compiler.h" 17 18ANDROID_BEGIN_HEADER 19 20// Set EINTR_WRAPPER_DEBUG to 1 to force the debug version of HANDLE_EINTR 21// which will call android_eintr_wrapper_fatal() is the system call loops 22// too many times, or 0 to get it to loop indefinitly. 23// Mostly used for unit testing. 24// If the macro is undefined, auto-detect the value based on NDEBUG. 25#if !defined(EINTR_WRAPPER_DEBUG) 26# ifdef NDEBUG 27# define EINTER_WRAPPER_DEBUG 0 28# else 29# define EINTR_WRAPPER_DEBUG 1 30# endif 31#endif 32 33// HANDLE_EINTR() is a macro used to handle EINTR return values when 34// calling system calls like open() or read() on Posix systems. 35// 36// By default, this will loop indefinitly, retrying the call until 37// the result is no longer -1/EINTR, except in debug mode, where a 38// loop counter is actually used and to provoke a fatal error if there 39// are too many loops. 40// 41// Usage example: 42// int ret = HANDLE_EINTR(open("/some/file/path", O_RDONLY)); 43// 44// IMPORTANT: Do not use with the close() system call (use IGNORE_EINTR() 45// instead). 46// 47// - On Linux, the file descriptor is always already closed when this 48// function returns -1/EINTR, and calling it again with the same 49// parameters risks closing another file descriptor open by another 50// thread in parallel! 51// 52// - On OS X, whether the file descriptor is closed or not is pretty 53// much random! It's better to leave the descriptor open than risk 54// closing another one by mistake :( 55// 56#ifdef _WIN32 57# define HANDLE_EINTR(x) (x) 58#elif EINTR_WRAPPER_DEBUG == 0 59# define HANDLE_EINTR(x) \ 60 __extension__ ({ \ 61 __typeof__(x) eintr_wrapper_result; \ 62 do { \ 63 eintr_wrapper_result = (x); \ 64 } while (eintr_wrapper_result < 0 && errno == EINTR); \ 65 eintr_wrapper_result; \ 66 }) 67#else // !_WIN32 && EINTR_WRAPPER_DEBUG 68 69# define MAX_EINTR_LOOP_COUNT 100 70 71# define HANDLE_EINTR(x) \ 72 __extension__ ({ \ 73 __typeof__(x) eintr_wrapper_result; \ 74 int eintr_wrapper_loop_count = 0; \ 75 for (;;) { \ 76 eintr_wrapper_result = (x); \ 77 if (eintr_wrapper_result != -1 || errno != EINTR) \ 78 break; \ 79 if (++eintr_wrapper_loop_count >= MAX_EINTR_LOOP_COUNT) { \ 80 android_eintr_wrapper_fatal( \ 81 __FILE__,__LINE__,__PRETTY_FUNCTION__,#x); \ 82 } \ 83 }; \ 84 eintr_wrapper_result; \ 85 }) 86#endif // !_WIN32 && EINTR_WRAPPER_DEBUG 87 88// IGNORE_EINTR() is a macro used to perform a system call and ignore 89// an EINTR result, i.e. it will return 0 instead of -1 if this occurs. 90// This is mostly used with the close() system call, as described 91// in the HANDLE_EINTR() documentation. 92#ifdef _WIN32 93# define IGNORE_EINTR(x) (x) 94#else 95# define IGNORE_EINTR(x) \ 96 __extension__ ({ \ 97 __typeof__(x) eintr_wrapper_result = (x); \ 98 if (eintr_wrapper_result == -1 && errno == EINTR) \ 99 eintr_wrapper_result = 0; \ 100 eintr_wrapper_result; \ 101 }) 102#endif 103 104#ifndef _WIN32 105// This function is called in debug mode only when a system call wrapped 106// by HANDLE_EINTR() failed more than MAX_EINTR_LOOP_COUNT times. 107// |file| is the source file location. 108// |lineno| is the line number in the source file. 109// |function| is the name of the function, or NULL if not available. 110// |call| is a string describing the system call that failed. 111void __attribute__((noreturn)) android_eintr_wrapper_fatal( 112 const char* file, 113 long lineno, 114 const char* function, 115 const char* call); 116#endif // !_WIN32 117 118ANDROID_END_HEADER 119 120#endif // ANDROID_UTILS_EINTR_WRAPPER_H 121