From patchwork Fri Oct 12 06:31:55 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Honnappa Nagarahalli X-Patchwork-Id: 148719 Delivered-To: patch@linaro.org Received: by 2002:a2e:8595:0:0:0:0:0 with SMTP id b21-v6csp368329lji; Thu, 11 Oct 2018 23:32:44 -0700 (PDT) X-Google-Smtp-Source: ACcGV63G7sSBuPtOf76Hy+0pCP3NEhLR7rk0R3N118ANaXTZzIOLIjBl1Ot4mNjTJ42hhEcUrki7 X-Received: by 2002:a17:906:4054:: with SMTP id y20-v6mr5667358ejj.30.1539325964301; Thu, 11 Oct 2018 23:32:44 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1539325964; cv=none; d=google.com; s=arc-20160816; b=zUp6c3BqgZ4I9d2BIIry1dztf0L6ZMfslVqDir7hlfngl+COrKfhzRlEBhWQp0Z2/5 1NK1Z4CSN+uZOBrP1gmrY1pf7EREkpGV2gQSRHar5qorMumEvSxDKZUS0kHuC3R6RG4L HgVDgnIN89qAlJ6wIolFpDOOnrPXnlmmIzTEg5A1WlTaoi6aVmalzjtzy4hWT8W5tRdP IgddC8vYg3j5zfx8r+DUnYA7FdI1afw2NkRi9O+p1uSD2NzWncdD/MOzbB2EM1mwdQ6r AQy9DgRGuMdyzCnfi6uh5xbjt9MEcprZUlNWIL4jE9GYNZdrFB4ELQR01VTdSuXv1P6a SaTQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=sender:errors-to:list-subscribe:list-help:list-post:list-archive :list-unsubscribe:list-id:precedence:subject:references:in-reply-to :message-id:date:cc:to:from; bh=qWhOBAlssDRz487JVtPXhVqwxkb7ne5CMna0DZ6fHww=; b=GNhRmwxT5FidCIv8lPqk2Cttz4aVbZwTJdW87onHo7lDagmUHwCp8Exx14+LdEkeKt BQXXSlAIsxfhS+4REL6MK+NnuTQKsSsIPJCO591MwPIHst9168hrFSkUMpDf8BQD9rYn FVWqN/SYZNq9F6Wqqnwy51ELRd/OEANjvf2m8dZiQHr2fYFWJp5vTLanHqrehZnHjxCg cujnS/QgMsRJfndF2Tt2OssqnWsk7CbM7Jyb3/q0FFxiAQUwW5O7215cm4QyQNW8CNLB 90VSvMQbVIoe+bDf3+MpJuWU/qIGGemhpDib31eldEFq0mEe1ZvZ/aEQ5LdqLE/7D14C 3LBA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of dev-bounces@dpdk.org designates 92.243.14.124 as permitted sender) smtp.mailfrom=dev-bounces@dpdk.org Return-Path: Received: from dpdk.org (dpdk.org. [92.243.14.124]) by mx.google.com with ESMTP id k9-v6si591239eds.404.2018.10.11.23.32.44; Thu, 11 Oct 2018 23:32:44 -0700 (PDT) Received-SPF: pass (google.com: domain of dev-bounces@dpdk.org designates 92.243.14.124 as permitted sender) client-ip=92.243.14.124; Authentication-Results: mx.google.com; spf=pass (google.com: domain of dev-bounces@dpdk.org designates 92.243.14.124 as permitted sender) smtp.mailfrom=dev-bounces@dpdk.org Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id F17671B122; Fri, 12 Oct 2018 08:32:18 +0200 (CEST) Received: from foss.arm.com (foss.arm.com [217.140.101.70]) by dpdk.org (Postfix) with ESMTP id 3BAF41B103 for ; Fri, 12 Oct 2018 08:32:12 +0200 (CEST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A055C15BF; Thu, 11 Oct 2018 23:32:11 -0700 (PDT) Received: from 2p2660v4-1.austin.arm.com (2p2660v4-1.austin.arm.com [10.118.12.190]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3B2D13F5B3; Thu, 11 Oct 2018 23:32:11 -0700 (PDT) From: Honnappa Nagarahalli To: bruce.richardson@intel.com, pablo.de.lara.guarch@intel.com Cc: dev@dpdk.org, yipeng1.wang@intel.com, honnappa.nagarahalli@arm.com, dharmik.thakkar@arm.com, gavin.hu@arm.com, nd@arm.com Date: Fri, 12 Oct 2018 01:31:55 -0500 Message-Id: <1539325918-125438-5-git-send-email-honnappa.nagarahalli@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1539325918-125438-1-git-send-email-honnappa.nagarahalli@arm.com> References: <1539325918-125438-1-git-send-email-honnappa.nagarahalli@arm.com> Subject: [dpdk-dev] [PATCH v3 4/7] hash: add memory ordering to avoid race conditions X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Only race condition that can occur is - using the key store element before the key write is completed. Hence, while inserting the element the release memory order is used. Any other race condition is caught by the key comparison. Memory orderings are added only where needed. For ex: reads in the writer's context do not need memory ordering as there is a single writer. key_idx in the bucket entry and pdata in the key store element are used for synchronisation. key_idx is used to release an inserted entry in the bucket to the reader. Use of pdata for synchronisation is required due to updation of an existing entry where-in only the pdata is updated without updating key_idx. Signed-off-by: Honnappa Nagarahalli Reviewed-by: Gavin Hu Reviewed-by: Ola Liljedahl Reviewed-by: Steve Capper Reviewed-by: Yipeng Wang --- lib/librte_hash/rte_cuckoo_hash.c | 116 ++++++++++++++++++++++++++++---------- 1 file changed, 87 insertions(+), 29 deletions(-) -- 2.7.4 diff --git a/lib/librte_hash/rte_cuckoo_hash.c b/lib/librte_hash/rte_cuckoo_hash.c index 13646d0..e55725a 100644 --- a/lib/librte_hash/rte_cuckoo_hash.c +++ b/lib/librte_hash/rte_cuckoo_hash.c @@ -1,5 +1,6 @@ /* SPDX-License-Identifier: BSD-3-Clause * Copyright(c) 2010-2016 Intel Corporation + * Copyright(c) 2018 Arm Limited */ #include @@ -585,7 +586,9 @@ enqueue_slot_back(const struct rte_hash *h, rte_ring_sp_enqueue(h->free_slots, slot_id); } -/* Search a key from bucket and update its data */ +/* Search a key from bucket and update its data. + * Writer holds the lock before calling this. + */ static inline int32_t search_and_update(const struct rte_hash *h, void *data, const void *key, struct rte_hash_bucket *bkt, uint16_t sig) @@ -598,8 +601,13 @@ search_and_update(const struct rte_hash *h, void *data, const void *key, k = (struct rte_hash_key *) ((char *)keys + bkt->key_idx[i] * h->key_entry_size); if (rte_hash_cmp_eq(key, k->key, h) == 0) { - /* Update data */ - k->pdata = data; + /* 'pdata' acts as the synchronization point + * when an existing hash entry is updated. + * Key is not updated in this case. + */ + __atomic_store_n(&k->pdata, + data, + __ATOMIC_RELEASE); /* * Return index where key is stored, * subtracting the first dummy index @@ -655,7 +663,15 @@ rte_hash_cuckoo_insert_mw(const struct rte_hash *h, /* Check if slot is available */ if (likely(prim_bkt->key_idx[i] == EMPTY_SLOT)) { prim_bkt->sig_current[i] = sig; - prim_bkt->key_idx[i] = new_idx; + /* Key can be of arbitrary length, so it is + * not possible to store it atomically. + * Hence the new key element's memory stores + * (key as well as data) should be complete + * before it is referenced. + */ + __atomic_store_n(&prim_bkt->key_idx[i], + new_idx, + __ATOMIC_RELEASE); break; } } @@ -739,8 +755,10 @@ rte_hash_cuckoo_move_insert_mw(const struct rte_hash *h, */ curr_bkt->sig_current[curr_slot] = prev_bkt->sig_current[prev_slot]; - curr_bkt->key_idx[curr_slot] = - prev_bkt->key_idx[prev_slot]; + /* Release the updated bucket entry */ + __atomic_store_n(&curr_bkt->key_idx[curr_slot], + prev_bkt->key_idx[prev_slot], + __ATOMIC_RELEASE); curr_slot = prev_slot; curr_node = prev_node; @@ -748,7 +766,10 @@ rte_hash_cuckoo_move_insert_mw(const struct rte_hash *h, } curr_bkt->sig_current[curr_slot] = sig; - curr_bkt->key_idx[curr_slot] = new_idx; + /* Release the new bucket entry */ + __atomic_store_n(&curr_bkt->key_idx[curr_slot], + new_idx, + __ATOMIC_RELEASE); __hash_rw_writer_unlock(h); @@ -889,8 +910,15 @@ __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key, new_idx = (uint32_t)((uintptr_t) slot_id); /* Copy key */ rte_memcpy(new_k->key, key, h->key_len); - new_k->pdata = data; - + /* Key can be of arbitrary length, so it is not possible to store + * it atomically. Hence the new key element's memory stores + * (key as well as data) should be complete before it is referenced. + * 'pdata' acts as the synchronization point when an existing hash + * entry is updated. + */ + __atomic_store_n(&new_k->pdata, + data, + __ATOMIC_RELEASE); /* Find an empty slot and insert */ ret = rte_hash_cuckoo_insert_mw(h, prim_bkt, sec_bkt, key, data, @@ -1034,21 +1062,27 @@ search_one_bucket(const struct rte_hash *h, const void *key, uint16_t sig, void **data, const struct rte_hash_bucket *bkt) { int i; + uint32_t key_idx; + void *pdata; struct rte_hash_key *k, *keys = h->key_store; for (i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) { - if (bkt->sig_current[i] == sig && - bkt->key_idx[i] != EMPTY_SLOT) { + key_idx = __atomic_load_n(&bkt->key_idx[i], + __ATOMIC_ACQUIRE); + if (bkt->sig_current[i] == sig && key_idx != EMPTY_SLOT) { k = (struct rte_hash_key *) ((char *)keys + - bkt->key_idx[i] * h->key_entry_size); + key_idx * h->key_entry_size); + pdata = __atomic_load_n(&k->pdata, + __ATOMIC_ACQUIRE); + if (rte_hash_cmp_eq(key, k->key, h) == 0) { if (data != NULL) - *data = k->pdata; + *data = pdata; /* * Return index where key is stored, * subtracting the first dummy index */ - return bkt->key_idx[i] - 1; + return key_idx - 1; } } } @@ -1173,21 +1207,25 @@ __rte_hash_compact_ll(struct rte_hash_bucket *cur_bkt, int pos) { } } -/* Search one bucket and remove the matched key */ +/* Search one bucket and remove the matched key. + * Writer is expected to hold the lock while calling this + * function. + */ static inline int32_t search_and_remove(const struct rte_hash *h, const void *key, struct rte_hash_bucket *bkt, uint16_t sig, int *pos) { struct rte_hash_key *k, *keys = h->key_store; unsigned int i; - int32_t ret; + uint32_t key_idx; /* Check if key is in bucket */ for (i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) { - if (bkt->sig_current[i] == sig && - bkt->key_idx[i] != EMPTY_SLOT) { + key_idx = __atomic_load_n(&bkt->key_idx[i], + __ATOMIC_ACQUIRE); + if (bkt->sig_current[i] == sig && key_idx != EMPTY_SLOT) { k = (struct rte_hash_key *) ((char *)keys + - bkt->key_idx[i] * h->key_entry_size); + key_idx * h->key_entry_size); if (rte_hash_cmp_eq(key, k->key, h) == 0) { bkt->sig_current[i] = NULL_SIGNATURE; /* Do not free the key store element if @@ -1196,13 +1234,16 @@ search_and_remove(const struct rte_hash *h, const void *key, if (h->recycle_on_del) remove_entry(h, bkt, i); - /* Return index where key is stored, + __atomic_store_n(&bkt->key_idx[i], + EMPTY_SLOT, + __ATOMIC_RELEASE); + + *pos = i; + /* + * Return index where key is stored, * subtracting the first dummy index */ - ret = bkt->key_idx[i] - 1; - bkt->key_idx[i] = EMPTY_SLOT; - *pos = i; - return ret; + return key_idx - 1; } } } @@ -1402,6 +1443,7 @@ __rte_hash_lookup_bulk(const struct rte_hash *h, const void **keys, uint32_t prim_hitmask[RTE_HASH_LOOKUP_BULK_MAX] = {0}; uint32_t sec_hitmask[RTE_HASH_LOOKUP_BULK_MAX] = {0}; struct rte_hash_bucket *cur_bkt, *next_bkt; + void *pdata[RTE_HASH_LOOKUP_BULK_MAX]; /* Prefetch first keys */ for (i = 0; i < PREFETCH_OFFSET && i < num_keys; i++) @@ -1480,18 +1522,25 @@ __rte_hash_lookup_bulk(const struct rte_hash *h, const void **keys, uint32_t hit_index = __builtin_ctzl(prim_hitmask[i]) >> 1; - uint32_t key_idx = primary_bkt[i]->key_idx[hit_index]; + uint32_t key_idx = + __atomic_load_n( + &primary_bkt[i]->key_idx[hit_index], + __ATOMIC_ACQUIRE); const struct rte_hash_key *key_slot = (const struct rte_hash_key *)( (const char *)h->key_store + key_idx * h->key_entry_size); + + if (key_idx != EMPTY_SLOT) + pdata[i] = __atomic_load_n(&key_slot->pdata, + __ATOMIC_ACQUIRE); /* * If key index is 0, do not compare key, * as it is checking the dummy slot */ if (!!key_idx & !rte_hash_cmp_eq(key_slot->key, keys[i], h)) { if (data != NULL) - data[i] = key_slot->pdata; + data[i] = pdata[i]; hits |= 1ULL << i; positions[i] = key_idx - 1; @@ -1504,11 +1553,19 @@ __rte_hash_lookup_bulk(const struct rte_hash *h, const void **keys, uint32_t hit_index = __builtin_ctzl(sec_hitmask[i]) >> 1; - uint32_t key_idx = secondary_bkt[i]->key_idx[hit_index]; + uint32_t key_idx = + __atomic_load_n( + &secondary_bkt[i]->key_idx[hit_index], + __ATOMIC_ACQUIRE); const struct rte_hash_key *key_slot = (const struct rte_hash_key *)( (const char *)h->key_store + key_idx * h->key_entry_size); + + if (key_idx != EMPTY_SLOT) + pdata[i] = __atomic_load_n(&key_slot->pdata, + __ATOMIC_ACQUIRE); + /* * If key index is 0, do not compare key, * as it is checking the dummy slot @@ -1516,7 +1573,7 @@ __rte_hash_lookup_bulk(const struct rte_hash *h, const void **keys, if (!!key_idx & !rte_hash_cmp_eq(key_slot->key, keys[i], h)) { if (data != NULL) - data[i] = key_slot->pdata; + data[i] = pdata[i]; hits |= 1ULL << i; positions[i] = key_idx - 1; @@ -1612,7 +1669,8 @@ rte_hash_iterate(const struct rte_hash *h, const void **key, void **data, uint32 idx = *next % RTE_HASH_BUCKET_ENTRIES; /* If current position is empty, go to the next one */ - while ((position = h->buckets[bucket_idx].key_idx[idx]) == EMPTY_SLOT) { + while ((position = __atomic_load_n(&h->buckets[bucket_idx].key_idx[idx], + __ATOMIC_ACQUIRE)) == EMPTY_SLOT) { (*next)++; /* End of table */ if (*next == total_entries)