On Mon, Nov 17, 2014 at 07:42:28PM +0100, Oleg Nesterov wrote:
> 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...
>
Most of the time when Smatch prints a warning about those then it's a
bug. It's a mix of precedence bugs and adding accidental negates.
I'll send a patch to put some parenthesis around the negate.
regards,
dan carpenter
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