149 lines
3.7 KiB
C++
149 lines
3.7 KiB
C++
/* Copyright (c) 2015 Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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#include "mysqld_daemon.h"
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#include "mysqld.h"
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#include "log.h"
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#include <unistd.h>
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#ifdef HAVE_SYS_WAIT_H
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#include <sys/wait.h>
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#endif
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/**
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Daemonize mysqld.
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This function does sysv style of daemonization of mysqld.
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@return - returns write end of the pipe file descriptor
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which is used to notify the parent to exit.
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*/
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int mysqld::runtime::mysqld_daemonize()
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{
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int pipe_fd[2];
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if (pipe(pipe_fd) < 0)
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return -1;
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pid_t pid= fork();
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if (pid == -1)
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{
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// Error
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close(pipe_fd[0]);
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close(pipe_fd[1]);
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return -1;
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}
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if (pid != 0)
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{
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// Parent, close write end of pipe.
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close(pipe_fd[1]);
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// Wait for first child to fork successfully.
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int rc,status;
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char waitstatus;
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while ((rc= waitpid(pid, &status, 0)) == -1 &&
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errno == EINTR)
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{
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// Retry if errno is EINTR.
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}
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if (rc == -1)
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{
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fprintf(stderr, "Unable to wait for process %lld\n",
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static_cast<long long>(pid));
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close(pipe_fd[0]);
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close(pipe_fd[1]);
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return -1;
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}
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// Exit parent on signal from grand child
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rc= read(pipe_fd[0], &waitstatus, 1);
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close(pipe_fd[0]);
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if (rc != 1)
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{
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fprintf(stderr, "Unable to determine if daemon is running: %s\n",
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strerror(errno));
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exit(MYSQLD_ABORT_EXIT);
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}
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else if (waitstatus != 1)
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{
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fprintf(stderr, "Initialization of mysqld failed: %d\n", waitstatus);
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exit(MYSQLD_ABORT_EXIT);
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}
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_exit(MYSQLD_SUCCESS_EXIT);
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}
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else
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{
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// Child, close read end of pipe file descriptor.
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close(pipe_fd[0]);
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int stdinfd;
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if ((stdinfd= open("/dev/null", O_RDONLY)) <= STDERR_FILENO)
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{
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close(pipe_fd[1]);
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exit(MYSQLD_ABORT_EXIT);
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}
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if (! (dup2(stdinfd, STDIN_FILENO) != STDIN_FILENO)
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&& (setsid() > -1))
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{
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close(stdinfd);
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pid_t grand_child_pid= fork();
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switch (grand_child_pid)
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{
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case 0: // Grand child
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return pipe_fd[1];
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case -1:
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close(pipe_fd[1]);
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_exit(MYSQLD_FAILURE_EXIT);
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default:
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_exit(MYSQLD_SUCCESS_EXIT);
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}
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}
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else
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{
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close(stdinfd);
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close(pipe_fd[1]);
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_exit(MYSQLD_SUCCESS_EXIT);
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}
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}
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}
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/**
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Signal parent to exit.
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@param pipe_write_fd File Descriptor of write end of pipe.
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@param status status of the initialization done by grand child.
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1 means initialization complete and the server
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is ready to accept client connections.
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0 means intialization aborted due to some failure.
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@note This function writes the status to write end of pipe.
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This notifies the parent which is block on read end of pipe.
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*/
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void mysqld::runtime::signal_parent(int pipe_write_fd, char status)
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{
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if (pipe_write_fd != -1)
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{
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while (write(pipe_write_fd, &status, 1) == -1 && errno == EINTR)
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{
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// Retry write syscall if errno is EINTR.
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}
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close(pipe_write_fd);
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}
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}
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