On Fri, 15 Jan 2016, Hannes Frederic Sowa wrote: > On 14.01.2016 23:20, Eric Dumazet wrote: > > On Thu, 2016-01-14 at 23:02 +0100, Hannes Frederic Sowa wrote: > > > > > We are just adding a second recursion limit solely to openvswitch which > > > has the same problem: > > > > > > https://patchwork.ozlabs.org/patch/566769/ > > > > > > This time also we depend on rcu_read_lock marking the section being > > > nonpreemptible. Nice would be a more generic solution here which doesn't > > > need to always add something to *current. > > > > > > Note that rcu_read_lock() does not imply that preemption is disabled. > > Exactly, it is conditional on CONFIG_PREEMPT_CPU/CONFIG_PREMPT_COUNT but > haven't thought about exactly that in this moment. Wrong. CONFIG_PREEMPT_RCU makes RCU preemptible. If that is not set then it fiddles with preempt_count when CONFIG_PREEMPT_COUNT=y. If CONFIG_PREEMPT_COUNT=n then you have a non preemptible system anyway. So you cannot assume that rcu_read_lock() disables preemption. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
