Messages in this thread |  | | | Date | Fri, 7 Jan 2005 16:15:28 -0800 (PST) | | From | Linus Torvalds <> | | Subject | Re: uselib() & 2.6.X? |
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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.
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