Re: rcu_read_lock lost its compiler barrier

From: Herbert Xu
Date: Thu Jun 06 2019 - 02:19:03 EST

On Wed, Jun 05, 2019 at 11:05:11PM -0700, Paul E. McKenney wrote:
> In case you were wondering, the reason that I was giving you such
> a hard time was that from what I could see, you were pushing for no
> {READ,WRITE}_ONCE() at all. ;-)

Hmm, that's exactly what it should be in net/ipv4/inet_fragment.c.
We don't need the READ_ONCE/WRITE_ONCE (or volatile marking) at
all. Even if the compiler dices and slices the reads/writes of
"a" into a thousand pieces, it should still work if the RCU
primitives are worth their salt.

But I do concede that in the general RCU case you must have the
READ_ONCE/WRITE_ONCE calls for rcu_dereference/rcu_assign_pointer.

Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
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