On Mon, Sep 21, 2020 at 04:26:39PM -0700, Paul E. McKenney wrote: > > > But this reasoning could apply to any data structure that contains > > a spin lock, in particular ones that are dereferenced through RCU. > > I lost you on this one. What is special about a spin lock? I don't know, that was Eric's concern. He is inferring that spin locks through lockdep debugging may trigger dependencies that require smp_load_acquire. Anyway, my point is if it applies to crng_node_pool then it would equally apply to RCU in general. > > So my question if this reasoning is valid, then why aren't we first > > converting rcu_dereference to use smp_load_acquire? > > For LTO in ARM, rumor has it that Will is doing so. Which was what > motivated the BoF on this topic at Linux Plumbers Conference. Sure, if RCU switches over to smp_load_acquire then I would have no problems with everybody else following in its footsteps. Here is the original patch in question: https://lore.kernel.org/lkml/20200916233042.51634-1-ebiggers@xxxxxxxxxx/ Cheers, -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
