From: Mathieu Desnoyers Date: Wed, 18 Apr 2012 20:05:29 +0000 (-0400) Subject: rculfhash: document linearizability guarantees X-Git-Tag: v0.7.0~31 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=0f5543cb1780acef35878646e6cdc966f1406c18;p=urcu.git rculfhash: document linearizability guarantees Signed-off-by: Mathieu Desnoyers --- diff --git a/rculfhash.c b/rculfhash.c index 6f470fd..d22b44d 100644 --- a/rculfhash.c +++ b/rculfhash.c @@ -98,6 +98,33 @@ * hash table nodes. These tables are invariant after they are * populated into the hash table. * + * Linearizability Guarantees: + * + * To discuss these guarantees, we first define "read" operations as any + * of the following operations surrounded by an RCU read-side lock/unlock + * pair: + * - cds_lfht_lookup + * - cds_lfht_lookup followed by iteration with cds_lfht_next_duplicate + * - cds_lfht_first followed iteration with cds_lfht_next + * + * We define "write" operations as any of cds_lfht_add, + * cds_lfht_add_unique, cds_lfht_add_replace, cds_lfht_del. + * + * The following guarantees are offered by this hash table: + * + * A) "read" after "write" will always return the result of the latest + * write. + * B) "write" after "read" will never be returned by the read. + * C) It is guaranteed that after a grace period following a "del" and + * "replace" operation, no reference to the removed items exists in + * the hash table. + * D) Uniqueness guarantee: when using add_unique and/or add_replace to + * insert nodes into the table, if there was previously one node or + * less with the same key being inserted by one or more concurrent + * add_unique and/or add_replace, all concurrent "read" performed on + * the hash table are guaranteed to find one, and only one node with + * that key. + * * Bucket node tables: * * hash table hash table the last all bucket node tables