Re: How to explain to lock validator: locking inodes in inode order

From: Arjan van de Ven
Date: Mon Jul 17 2006 - 23:30:12 EST

On Mon, 2006-07-17 at 19:24 -0700, Joshua Hudson wrote:
> Code does this:
> /* Lock two items. See locking.txt */
> static inline void kb0_lock2m(struct kb0_idata *m1, struct kb0_idata *m2)
> {
> if (m1->vi.i_ino > m2->vi.i_ino)
> mutex_lock(&m2->k_mutex);
> mutex_lock(&m1->k_mutex);
> if (m1->vi.i_ino < m2->vi.i_ino)
> mutex_lock(&m2->k_mutex);
> }
> Not sure how to explain to the lock validator that this code can never deadlock.

you're sure it can;t? (which fs is this btw?)

all places in the kernel that take this mutex in that order only do it
in i_ino order, including all directory operations like cross directory

(if so you can explain normal parent/child nesting, but only if so)

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