On 11/14, Dan Carpenter wrote:
>
> The patch eb6d8479b73d: "exit: reparent: cleanup the changing of
> ->parent" from Nov 13, 2014, leads to the following static checker
> warning:
>
> kernel/exit.c:543 forget_original_parent()
> warn: add some parenthesis here?
>
> kernel/exit.c
> 538 /* Can drop and reacquire tasklist_lock */
> 539 reaper = find_new_reaper(father);
> 540 list_for_each_entry(p, &father->children, sibling) {
> 541 for_each_thread(p, t) {
> 542 t->real_parent = reaper;
> 543 BUG_ON(!t->ptrace != (t->parent == father));
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> The reason for this warning is that many people forget that ! is higher
> precedence than ==.
Do you really think we should try to shut up this warning?
IMO this warning is wrong, "!A == B" or "!A != B" looks fine to me...
> This is a complicated condition however you write
> it, but it might be more clear to say:
>
> BUG_ON((!!t->ptrace) == (t->parent == father));
This is subjective, but to me it looks more confusing.
If we really want to "fix" it, I'd suggest
BUG_ON((!t->ptrace) != (t->parent == father));
Oleg.
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