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.