Thank you again for all your help Mathieu! Sent from my iPhone
> On Apr 15, 2021, at 3:26 PM, Mathieu Desnoyers > <mathieu.desnoy...@efficios.com> wrote: > > ----- On Apr 15, 2021, at 2:11 PM, lbj lbj...@yahoo.com wrote: > >> Thanks Mathieu. Is it safe to assume that if call_rcu is called twice then >> the >> callbacks are executed in the order that call_rcu was invoked? I think there >> is >> a queue and only one thread that QSBR uses to handle callbacks, i just wanted >> to make sure that the queue was a guaranteed fifo. > > It may very well depend on your configuration. For instance, if an application > invokes create_all_cpu_call_rcu_data(), it will create per-cpu worker threads > on each possible CPU. In that configuration, a given thread invoking > call_rcu() > twice (back to back) may be migrated from one CPU to another in between, hence > different call-rcu worker threads will be responsible for executing the > callbacks, > and they can be executed in any order. > > So even though by careful analysis of your specific application configuration > you > may presume that the callbacks will be executed in the same order they were > invoked, > this is not guaranteed by the API, so I would not recommend relying on FIFO > order > assumptions. > > And given that the call_rcu API does not guarantee FIFO order, we could > eventually > decide to change the order of callback execution from FIFO to LIFO if it > leads to > performance improvements due to better cache locality. > > Thanks, > > Mathieu > > -- > Mathieu Desnoyers > EfficiOS Inc. > http://www.efficios.com _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
