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Date: Mon, 17 Jul 2006 21:19:57 -0700 From: "Joshua Hudson" <joshudson@...il.com> To: linux-kernel@...r.kernel.org Subject: Re: How to explain to lock validator: locking inodes in inode order On 7/17/06, Arjan van de Ven <arjan@...radead.org> wrote: > 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? Yes. It never takes a lock on any higher inode without holding the lock on a lower inode first. I have a full proof across the VFS+FS [see below]. > > 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 > rename? I had to disable the kernel's locking of multiple objects in namei.c using a new FS_ flag because it would actually deadlock for this filesystem. > (which fs is this btw?) Custom filesystem (kb0), not in any tree but mine. I am in progress with syncing it up to the latest kernel. If anybody really wants it, it is 70-odd K of bzip2-compressed code of filesystem + utilities. It's not ready for non-acedemic use though. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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