: Today I noticed that setsid() didn't work anymore. This is due to
: a change in 2.0.1. I know that around that time some patches went in
: to let Linux comform more to POSIX, so that may be the cause. This
: is what changed:
: diff -u --recursive --new-file v2.0.0/linux/kernel/sys.c linux/kernel/sys.c
: --- v2.0.0/linux/kernel/sys.c Thu Jun 6 17:42:38 1996
: +++ linux/kernel/sys.c Tue Jul 2 19:08:43 1996
: @@ -634,8 +634,13 @@
:
: asmlinkage int sys_setsid(void)
: {
: - if (current->leader)
: - return -EPERM;
: + struct task_struct * p;
: +
: + for_each_task(p) {
: + if (p->pgrp == current->pid)
: + return -EPERM;
: + }
: +
: Now a process that gets spawned by a shell that sets up the process group
: for it (so it's the leader of it's own group, not session) cannot do
: a setsid() anymore because the "if (p->pgrp == current->pid)" check will
: match on itself.
: I now do a "setpgrp(0, getpgid(getppid()))" before setsid() and that works,
: but I think the check should be
: if (p != current && p->pgrp == current->pid)
: return -EPERM;
: But that could easily break POSIX conformance, I don't know...
You are quite right, and your version is POSIX conformant, not the kernel.
POSIX 4.3.2.4 reads:
EPERM The calling process is already a process group leader,
or the process group ID of a process other than the calling
process matches the process ID of the calling process.
Andries