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MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, 22 Aug 2019 15:43:49 +0300, Vlad Buslov wrote: > diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c > index 02a547aa77c0..bda42f1b5514 100644 > --- a/net/sched/cls_api.c > +++ b/net/sched/cls_api.c > @@ -3076,11 +3076,28 @@ __tc_setup_cb_call(struct tcf_block *block, enum tc_setup_type type, > int tc_setup_cb_call(struct tcf_block *block, enum tc_setup_type type, > void *type_data, bool err_stop, bool rtnl_held) > { > + bool take_rtnl = false; Should we perhaps speculatively: bool take_rtnl = READ_ONCE(block->lockeddevcnt); here? It shouldn't hurt, really, and otherwise every offload that requires rtnl will have to re-lock cb_lock, every single time.. > int ok_count; > > +retry: > + if (take_rtnl) > + rtnl_lock(); > down_read(&block->cb_lock); > + /* Need to obtain rtnl lock if block is bound to devs that require it. > + * In block bind code cb_lock is obtained while holding rtnl, so we must > + * obtain the locks in same order here. > + */ > + if (!rtnl_held && !take_rtnl && block->lockeddevcnt) { > + up_read(&block->cb_lock); > + take_rtnl = true; > + goto retry; > + } > + > ok_count = __tc_setup_cb_call(block, type, type_data, err_stop); > + > up_read(&block->cb_lock); > + if (take_rtnl) > + rtnl_unlock(); > return ok_count; > } > EXPORT_SYMBOL(tc_setup_cb_call);