Re: [patch 24/52] fs: dcache reduce d_parent locking

From: Nick Piggin
Date: Thu Jun 24 2010 - 11:07:42 EST

On Thu, Jun 24, 2010 at 10:44:22AM +0200, Peter Zijlstra wrote:
> On Thu, 2010-06-24 at 13:02 +1000, npiggin@xxxxxxx wrote:
> > Use RCU property of dcache to simplify locking in some places where we
> > take d_parent and d_lock.
> >
> > Comment: don't need rcu_deref because we take the spinlock and recheck it.
> But does the LOCK barrier imply a DATA DEPENDENCY barrier? (It does on
> x86, and the compiler barrier implied by spin_lock() suffices to replace

Well the dependency we care about is from loading the parent pointer
to acquiring its spinlock. But we can't possibly have stale data given
to the spin lock operation itself because it is a RMW.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at