I am trying to write a function that spawns a child process, lets it run for a certain amount of time and then kills it if it hasn't finished:
int sysExecTimeout(const char * exePath, int timeoutSec);
In the function, I use fork
and execl
to spawn the child, and, when it times out, I use kill(pid, SIGTERM)
and kill(pid, SIGKILL)
after 2 seconds, to ensure the child dies:
pid_t pid = fork();
if(pid == 0) {
execl("/bin/sh", "sh", "-c", exePath);
exit(127);
} else if(pid != -1) {
// timeout code
if(timeout) {
kill(pid, SIGTERM);
sleep(2);
kill(pid, SIGKILL);
}
}
I am using Linux, and it seems that when a parent process dies, the child is not killed automatically. So the two kill
calls will just kill the /bin/sh
process and leave the exePath
command running, since it is a child process of /bin/sh
.
I am trying to write the sysExecTimeout
function such that it kills the entire process tree rooted at pid
, where pid
is the PID from pid = fork()
I need this because the exePath
command will spawn other commands, which can also spawn other commands, which could get stuck and consume resources.
I do not have control over the exePath
binaries/scripts that get executed, so I cannot write my own parent-dies-so-kill-the-children logic in them.
I tried using kill(0, SIGTERM)
, which almost did the job, except it also killed my own process :)
I am wondering if there is a flag I can turn on programatically in C that says "hey man, when I die, take all my children and kill them, and repeat recursively for their children" such that the entire process tree started from that program dies (assuming the PID/PPID chain can be followed).
I could use that flag here:
if(pid == 0) {
turnOnRecursiveDeathFlag();
system(exePath);
//execl("/bin/sh", "sh", "-c", exePath);
exit(127);
}
Is there a way to do that? I've been searching for a while, but all I can find are hacks using ps -ef
, or modifying the children processes that you are running etc.
Use setpgid in the child to set its GPID equal to its own PID. The parent then can kill(-pid,...) to signal the entire group.
pid_t pid = fork();
if(pid == 0) {
setpgid(0, 0);
execl("/bin/sh", "sh", "-c", exePath);
exit(127);
} else if(pid == -1) {
// timeout code
if(timeout) {
kill(-pid, SIGTERM);
sleep(2);
kill(-pid, SIGKILL);
}
}
That should do it.
One more thing, when you spawn a shell, make sure it doesn't enable job control. Otherwise, it will create its own process groups. Your "/bin/sh -c" is fine.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.