Re: [PATCH] pid: change task_struct::pid to read-only
Richard, Peter,
sorry I deleted your emails by accident, so I am replying to my email.
Sure, ASSIGN_CONST() looks "dangerous". Still to me it is safer than
"(pid_t*)&(tsk->pid)" done by hand. And yes, it is visible to grep.
But the main point, it is much more readable. Just look at the change
below,
On 12/17, Oleg Nesterov wrote:
> > if (!thread_group_leader(tsk)) {
> > struct task_struct *leader = tsk->group_leader;
> > + /* tast_struct::pid is const pid_t, hence the ugly cast */
> > + pid_t *pid_p = (pid_t*)&(tsk->pid);
> >
> > sig->notify_count = -1; /* for exit_notify() */
> > for (;;) {
> > @@ -950,7 +952,7 @@ static int de_thread(struct task_struct *tsk)
> > * Note: The old leader also uses this pid until release_task
> > * is called. Odd but simple and correct.
> > */
> > - tsk->pid = leader->pid;
> > + *pid_p = leader->pid;
Isn't it ugly to add the temporary? And this temporary is the pointer.
ASSIGN_CONST(task->pid, leader->pid) is self-documenting and clear.
The only problem is that
#define ASSIGN_CONST(l, r) (*(typeof(r) *)&(l) = (r))
obviously can't work in this case ;) We need something more clever.
Oleg.