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  • Committer: Bazaar Package Importer
  • Author(s): Ondřej Surý
  • Date: 2011-04-20 17:36:48 UTC
  • Revision ID: james.westby@ubuntu.com-20110420173648-ifergoxyrm832trd
Tags: upstream-2011.03.07.1
Import upstream version 2011.03.07.1

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src/lib9/rfork.c
 
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/*
 
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Plan 9 from User Space src/lib9/rfork.c
 
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http://code.swtch.com/plan9port/src/tip/src/lib9/rfork.c
 
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Copyright 2001-2007 Russ Cox.  All Rights Reserved.
 
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Permission is hereby granted, free of charge, to any person obtaining a copy
 
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of this software and associated documentation files (the "Software"), to deal
 
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in the Software without restriction, including without limitation the rights
 
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 
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copies of the Software, and to permit persons to whom the Software is
 
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furnished to do so, subject to the following conditions:
 
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The above copyright notice and this permission notice shall be included in
 
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all copies or substantial portions of the Software.
 
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
 
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 
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THE SOFTWARE.
 
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*/
 
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#include <u.h>
 
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#include <sys/wait.h>
 
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#include <signal.h>
 
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#include <libc.h>
 
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#undef rfork
 
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static void
 
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nop(int x)
 
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{
 
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        USED(x);
 
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}
 
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int
 
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p9rfork(int flags)
 
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{
 
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        int pid, status;
 
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        int p[2];
 
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        int n;
 
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        char buf[128], *q;
 
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        extern char **environ;
 
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        if((flags&(RFPROC|RFFDG|RFMEM)) == (RFPROC|RFFDG)){
 
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                /* check other flags before we commit */
 
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                flags &= ~(RFPROC|RFFDG|RFENVG);
 
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                n = (flags & ~(RFNOTEG|RFNAMEG|RFNOWAIT|RFCENVG));
 
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                if(n){
 
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                        werrstr("unknown flags %08ux in rfork", n);
 
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                        return -1;
 
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                }
 
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                if(flags&RFNOWAIT){
 
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                        /*
 
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                         * BUG - should put the signal handler back after we
 
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                         * finish, but I just don't care.  If a program calls with
 
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                         * NOWAIT once, they're not likely to want child notes
 
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                         * after that.
 
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                         */
 
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                        signal(SIGCHLD, nop);
 
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                        if(pipe(p) < 0)
 
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                                return -1;
 
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                }
 
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                pid = fork();
 
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                if(pid == -1)
 
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                        return -1;
 
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                if(flags&RFNOWAIT){
 
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                        flags &= ~RFNOWAIT;
 
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                        if(pid){
 
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                                /*
 
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                                 * Parent - wait for child to fork wait-free child.
 
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                                 * Then read pid from pipe.  Assume pipe buffer can absorb the write.
 
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                                 */
 
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                                close(p[1]);
 
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                                status = 0;
 
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                                if(wait4(pid, &status, 0, 0) < 0){
 
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                                        werrstr("pipe dance - wait4 - %r");
 
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                                        close(p[0]);
 
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                                        return -1;
 
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                                }
 
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                                n = readn(p[0], buf, sizeof buf-1);
 
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                                close(p[0]);
 
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                                if(!WIFEXITED(status) || WEXITSTATUS(status)!=0 || n <= 0){
 
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                                        if(!WIFEXITED(status))
 
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                                                werrstr("pipe dance - !exited 0x%ux", status);
 
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                                        else if(WEXITSTATUS(status) != 0)
 
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                                                werrstr("pipe dance - non-zero status 0x%ux", status);
 
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                                        else if(n < 0)
 
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                                                werrstr("pipe dance - pipe read error - %r");
 
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                                        else if(n == 0)
 
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                                                werrstr("pipe dance - pipe read eof");
 
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                                        else
 
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                                                werrstr("pipe dance - unknown failure");
 
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                                        return -1;
 
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                                }
 
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                                buf[n] = 0;
 
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                                if(buf[0] == 'x'){
 
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                                        werrstr("%s", buf+2);
 
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                                        return -1;
 
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                                }
 
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                                pid = strtol(buf, &q, 0);
 
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                        }else{
 
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                                /*
 
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                                 * Child - fork a new child whose wait message can't
 
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                                 * get back to the parent because we're going to exit!
 
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                                 */
 
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                                signal(SIGCHLD, SIG_IGN);
 
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                                close(p[0]);
 
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                                pid = fork();
 
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                                if(pid){
 
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                                        /* Child parent - send status over pipe and exit. */
 
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                                        if(pid > 0)
 
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                                                fprint(p[1], "%d", pid);
 
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                                        else
 
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                                                fprint(p[1], "x %r");
 
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                                        close(p[1]);
 
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                                        _exit(0);
 
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                                }else{
 
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                                        /* Child child - close pipe. */
 
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                                        close(p[1]);
 
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                                }
 
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                        }
 
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                }
 
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                if(pid != 0)
 
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                        return pid;
 
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                if(flags&RFCENVG)
 
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                        if(environ)
 
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                                *environ = nil;
 
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        }
 
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        if(flags&RFPROC){
 
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                werrstr("cannot use rfork for shared memory -- use libthread");
 
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                return -1;
 
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        }
 
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        if(flags&RFNAMEG){
 
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                /* XXX set $NAMESPACE to a new directory */
 
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                flags &= ~RFNAMEG;
 
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        }
 
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        if(flags&RFNOTEG){
 
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                setpgid(0, getpid());
 
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                flags &= ~RFNOTEG;
 
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        }
 
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        if(flags&RFNOWAIT){
 
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                werrstr("cannot use RFNOWAIT without RFPROC");
 
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                return -1;
 
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        }
 
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        if(flags){
 
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                werrstr("unknown flags %08ux in rfork", flags);
 
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                return -1;
 
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        }
 
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        return 0;
 
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}