diff options
Diffstat (limited to 'src/lib9/rfork.c')
| -rw-r--r-- | src/lib9/rfork.c | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/src/lib9/rfork.c b/src/lib9/rfork.c new file mode 100644 index 000000000..c9d632189 --- /dev/null +++ b/src/lib9/rfork.c @@ -0,0 +1,153 @@ +/* +Plan 9 from User Space src/lib9/rfork.c +http://code.swtch.com/plan9port/src/tip/src/lib9/rfork.c + +Copyright 2001-2007 Russ Cox. All Rights Reserved. + +Permission is hereby granted, free of charge, to any person obtaining a copy +of this software and associated documentation files (the "Software"), to deal +in the Software without restriction, including without limitation the rights +to use, copy, modify, merge, publish, distribute, sublicense, and/or sell +copies of the Software, and to permit persons to whom the Software is +furnished to do so, subject to the following conditions: + +The above copyright notice and this permission notice shall be included in +all copies or substantial portions of the Software. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN +THE SOFTWARE. +*/ + +#include <u.h> +#include <sys/wait.h> +#include <signal.h> +#include <libc.h> +#undef rfork + +static void +nop(int x) +{ + USED(x); +} + +int +p9rfork(int flags) +{ + int pid, status; + int p[2]; + int n; + char buf[128], *q; + extern char **environ; + + if((flags&(RFPROC|RFFDG|RFMEM)) == (RFPROC|RFFDG)){ + /* check other flags before we commit */ + flags &= ~(RFPROC|RFFDG|RFENVG); + n = (flags & ~(RFNOTEG|RFNAMEG|RFNOWAIT|RFCENVG)); + if(n){ + werrstr("unknown flags %08ux in rfork", n); + return -1; + } + if(flags&RFNOWAIT){ + /* + * BUG - should put the signal handler back after we + * finish, but I just don't care. If a program calls with + * NOWAIT once, they're not likely to want child notes + * after that. + */ + signal(SIGCHLD, nop); + if(pipe(p) < 0) + return -1; + } + pid = fork(); + if(pid == -1) + return -1; + if(flags&RFNOWAIT){ + flags &= ~RFNOWAIT; + if(pid){ + /* + * Parent - wait for child to fork wait-free child. + * Then read pid from pipe. Assume pipe buffer can absorb the write. + */ + close(p[1]); + status = 0; + if(wait4(pid, &status, 0, 0) < 0){ + werrstr("pipe dance - wait4 - %r"); + close(p[0]); + return -1; + } + n = readn(p[0], buf, sizeof buf-1); + close(p[0]); + if(!WIFEXITED(status) || WEXITSTATUS(status)!=0 || n <= 0){ + if(!WIFEXITED(status)) + werrstr("pipe dance - !exited 0x%ux", status); + else if(WEXITSTATUS(status) != 0) + werrstr("pipe dance - non-zero status 0x%ux", status); + else if(n < 0) + werrstr("pipe dance - pipe read error - %r"); + else if(n == 0) + werrstr("pipe dance - pipe read eof"); + else + werrstr("pipe dance - unknown failure"); + return -1; + } + buf[n] = 0; + if(buf[0] == 'x'){ + werrstr("%s", buf+2); + return -1; + } + pid = strtol(buf, &q, 0); + }else{ + /* + * Child - fork a new child whose wait message can't + * get back to the parent because we're going to exit! + */ + signal(SIGCHLD, SIG_IGN); + close(p[0]); + pid = fork(); + if(pid){ + /* Child parent - send status over pipe and exit. */ + if(pid > 0) + fprint(p[1], "%d", pid); + else + fprint(p[1], "x %r"); + close(p[1]); + _exit(0); + }else{ + /* Child child - close pipe. */ + close(p[1]); + } + } + } + if(pid != 0) + return pid; + if(flags&RFCENVG) + if(environ) + *environ = nil; + } + if(flags&RFPROC){ + werrstr("cannot use rfork for shared memory -- use libthread"); + return -1; + } + if(flags&RFNAMEG){ + /* XXX set $NAMESPACE to a new directory */ + flags &= ~RFNAMEG; + } + if(flags&RFNOTEG){ + setpgid(0, getpid()); + flags &= ~RFNOTEG; + } + if(flags&RFNOWAIT){ + werrstr("cannot use RFNOWAIT without RFPROC"); + return -1; + } + if(flags){ + werrstr("unknown flags %08ux in rfork", flags); + return -1; + } + return 0; +} |