On 13/12/20, Oleg Nesterov wrote:
> Richard, Peter,
Oleg,
> sorry I deleted your emails by accident, so I am replying to my email.
That's ok, you could send yourself a new copy from the "forward" link
here:
https://lkml.org/lkml/2013/12/20/277
> 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,
I completely agree it is more readable and safer, if it works.
> 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.
Go for it. I'll just stick with what I found works. I gave it a shot
to do it in one step and failed. I moved on.
> Oleg.
- RGB
--
Richard Guy Briggs <rbri...@redhat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red
Hat
Remote, Ottawa, Canada
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