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DateFri, 7 Jan 2005 16:15:28 -0800 (PST)
FromLinus Torvalds <>
SubjectRe: uselib() & 2.6.X?


On Fri, 7 Jan 2005, Alan Cox wrote:
>
> Please don't use that for mainline - do_brk_locked doesn't follow kernel
> convention

I agree, I also find the "do_brk_locked()" naming confusing. To me it
implies that we already _are_ locked, not that we're going to lock.

On the other hand, I think Alan's patch is equally confusing: the calling
rules for "do_brk()" and "do_mmap()" are the same, and they are "caller
takes mmap_sem".

So I think you _both_ broke kernel conventions.

So I'd personally much prefer to just first fix the bug minimally (by just
taking the lock in the two places that need it), and then _separately_ say
"we should warn if anybody ever calls 'do_brk()' without the lock". That's
how we tend to verify locking in other cases, ie we have things like

if (!spin_is_locked(&t->sighand->siglock))
BUG();
to verify the calling conventions. Same would go for mmap_sem (although we
don't seem to have any "sem_is_writelocked()" test - although you can fake
it with

if (down_read_trylock(&mm->mmap_sem))
BUG();
instead.

Now _that_ is a non-silent failure mode. The machine doesn't just silently
deadlock: it tells you exactly what's wrong.

Linus
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