On CentOS 6.3, In my main program I mount a Truecrypt volume containing executables A and B to a mount point, ./tmpfolder. I run program A, by doing
system("./tmpfolder/A")
from a forked child.
Program A does:
if (fork() == 0){
system("cp ./tmpfolder/B /tmp");
chdir("/tmp");
execl("/tmp/B", "B", (char *)0);
exit(0);
}
At this point program A exits, leaving program B running. So far so good.
Program B does:
chdir ("/tmp");
while(notdone){ /* do stuff */ }
Now I want to unmount the Truecrypt volume while leaving program B running. I cannot; the folder is in use.
After running A, ps shows B running, with PID 27643 (for example).
Then ls -l /proc/27643/cwd shows "/tmp". So the current working directory of B is not the mount point folder.
But my attempt to unmount fails: "device is busy".
And fuser -c ~/tmpfolder shows 27643, the PID of program B. So, somehow, program B is still using the mount point folder.
How can program B be still using the folder in which program A ran and then exited? How can I launch B without having it use the mount point folder?