[lttng-dev] QSBR urcu read lock question

Mathieu Desnoyers mathieu.desnoyers at efficios.com
Thu Apr 15 08:20:42 EDT 2021

----- On Apr 13, 2021, at 11:19 PM, lttng-dev lttng-dev at lists.lttng.org wrote:

> Hello all,
> I have two different entities that are both protected by QSBR rcu: a policy and
> a hashtable. In the reclamation thread for the policy I would like to take a
> read lock so that I can safely iterate through the hashtable. I dont see
> anything wrong with this, but I just wanted to make sure it was ok since taking
> an rcu read lock in an rcu reclamation thread seems like it may be a bit
> suspect. Thanks for any insights, let me know if clarification is needed!

When you say "the reclamation thread for the policy", do you refer to a call-rcu
worker thread ?

Also, you are aware that RCU read-side lock/unlock are effectively no-ops for
QSBR rcu, right ?



Mathieu Desnoyers
EfficiOS Inc.

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