我有以下sigaction处理程序代码
void signal_term_handler(int sig)
{
int rc = async_lockf(pid_file, F_UNLCK);
if(rc) {
char piderr[] = "PID file unlock failed!\n";
write(STDOUT_FILENO, piderr, (sizeof(piderr))-1);
}
close(pid_file);
char exitmsg[] = "EXIT Daemon:TERM signal Received!\n";
write(STDOUT_FILENO, exitmsg, (sizeof(exitmsg))-1);
_exit(EXIT_SUCCESS); //async-signal-save exit
}
上述函数中的所有函数调用都是异步信号保存。即使async_lockf()
也是异步信号保存:
/*
* The code of async_lockf is copied from eglibc-2.11.3/io/lockf.c
* The lockf.c is under the terms of the GNU Lesser General Public
* Copyright (C) 1994,1996,1997,1998,2000,2003 Free Software Foundation, Inc.
* This file is part of the GNU C Library.
*/
int async_lockf(int fd, int cmd)
{
struct flock fl = {0};
/* async_lockf is always relative to the current file position. */
fl.l_whence = SEEK_CUR;
fl.l_start = 0;
fl.l_len = 0;
switch (cmd)
{
case F_TEST:
/* Test the async_lock: return 0 if FD is unlocked or locked by this process;
return -1, set errno to EACCES, if another process holds the lock. */
fl.l_type = F_RDLCK;
if (fcntl (fd, F_GETLK, &fl) < 0)
return -1;
if (fl.l_type == F_UNLCK || fl.l_pid == getpid ())
return 0;
errno = EACCES;
return -1;
case F_ULOCK:
fl.l_type = F_UNLCK;
cmd = F_SETLK;
break;
case F_LOCK:
fl.l_type = F_WRLCK;
cmd = F_SETLK;
break;
case F_TLOCK:
fl.l_type = F_WRLCK;
cmd = F_SETLK;
break;
default:
errno = EINVAL;
return -1;
}
/* async_lockf() is a cancellation point but so is fcntl() if F_SETLKW is
used. Therefore we don't have to care about cancellation here,
the fcntl() function will take care of it. */
return fcntl (fd, cmd, &fl);
}
如果我执行kill -15
命令,sigaction处理程序应该关闭应用程序,但有时我会让processus运行而不会退出。这很少发生。例如,如果我启动应用程序,然后我以kill -15
1000次停止,此行为将仅发生约5次
对这种奇怪行为的任何解释?为什么我的申请不存在?特别是我使用异步信号保存功能(_exit()
)来关闭进程
答案 0 :(得分:1)
要查看正在发生的情况,请尝试将strace
或gdb
附加到流程中,并查看其中的位置。我最好的猜测是,在执行阻塞操作时,您有代码屏蔽信号(sigprocmask
),从而阻止信号处理程序运行。