Re: [patch] nfs: fix locking in nfs/inode.c in nfs_free_open_context

Trond Myklebust
2007-07-25T17:28:59Z

On Wed, 2007-07-25 at 17:08 +0200, Christian Krafft wrote:

> Obviously the locking code in nfs_free_open_context is wrong.
> Checking the list for entries and removing the entry should be an atomic operation.

Wrong. It is quite safe to test the structure member ctx->list for
emptiness outside the spinlock because we have an explicit guarantee
that nobody else has a reference to this structure, plus the
atomic_dec_and_test() in kref_put() has acted as a memory barrier for
us.

> Also list_del_init should be used, because list_del will leave the empty list in
> an undefined condition.

Huh? We're freeing the context. It will _never_ _ever_ _ever_ be used
again. If anything tries to use ctx->list after this, then that is a
major bug.

Patch rejected...

Trond