[lttng-dev] Do updaters of a cds_lfht need to be synchronized?

Charles Jacobsen charles.jacobsen at primarydata.com
Mon Oct 31 16:01:17 UTC 2016


fyi, see below.


I hope I posed the question correctly.


________________________________
From: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
Sent: Monday, October 31, 2016 9:50 AM
To: Charles Jacobsen
Cc: lttng-dev
Subject: Re: [lttng-dev] Do updaters of a cds_lfht need to be synchronized?


----- On Oct 28, 2016, at 11:40 AM, Charles Jacobsen <charles.jacobsen at primarydata.com> wrote:

The documentation for the lock-free hash table does not mention anything about synchronizing updaters (e.g., with a lock):


https://lwn.net/Articles/573431/

https://lwn.net/Articles/573432/


The source for rculfhash (== cds_lfht?) also mentions in the comments that add and remove are lock free:


https://github.com/urcu/userspace-rcu/blob/master/src/rculfhash.c


Is it safe to assume that cds_lfht_add, cds_lfht_add_unique, and so on, *only* require a surrounding rcu read lock/unlock?


"lock free" is part of the name, so I would assume the answer is "yes".

Yes, this assumption is correct.

Thanks,

Mathieu





Thank you.



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Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

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