From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
To: "Wang, Yipeng1" <yipeng1.wang@intel.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>
Cc: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
"dev@dpdk.org" <dev@dpdk.org>,
"Gobriel, Sameh" <sameh.gobriel@intel.com>, nd <nd@arm.com>,
Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
Subject: Re: [dpdk-dev] [PATCH v4 1/4] hash: fix race condition in iterate
Date: Tue, 2 Oct 2018 04:26:59 +0000 [thread overview]
Message-ID: <AM6PR08MB3672168549D2B5DD5828B72F98E80@AM6PR08MB3672.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <D2C4A16CA39F7F4E8E384D204491D7A6614EA321@FMSMSX151.amr.corp.intel.com>
>
> >-----Original Message-----
> >From: Honnappa Nagarahalli [mailto:Honnappa.Nagarahalli@arm.com]
> >> @@ -1317,16 +1317,19 @@ rte_hash_iterate(const struct rte_hash *h,
> >> const void **key, void **data, uint32
> >> bucket_idx = *next / RTE_HASH_BUCKET_ENTRIES;
> >> idx = *next % RTE_HASH_BUCKET_ENTRIES;
> >>
> >> + __hash_rw_reader_lock(h);
> >This does not work well with the lock-less changes I am making. We
> >should leave the lock in its original position. Instead change the while loop as
> follows:
> >
> >while ((position = h->buckets[bucket_idx].key_idx[idx]) == EMPTY_SLOT)
> >
> >> /* If current position is empty, go to the next one */
> >> while (h->buckets[bucket_idx].key_idx[idx] == EMPTY_SLOT) {
> >> (*next)++;
> >> /* End of table */
> >> - if (*next == total_entries)
> >> + if (*next == total_entries) {
> >> + __hash_rw_reader_unlock(h);
> >> return -ENOENT;
> >> + }
> >> bucket_idx = *next / RTE_HASH_BUCKET_ENTRIES;
> >> idx = *next % RTE_HASH_BUCKET_ENTRIES;
> >> }
> >> - __hash_rw_reader_lock(h);
> >> +
> >> /* Get position of entry in key table */
> >> position = h->buckets[bucket_idx].key_idx[idx];
> >If we change the while loop as I suggested as above, we can remove this line.
> >
> >> next_key = (struct rte_hash_key *) ((char *)h->key_store +
>
> [Wang, Yipeng] Sorry that I did not realize you already have it in your patch
> set and I agree.
> Do you want to export it as a bug fix in your patch set? I will remove my
> change.
Sure, I will make a separate commit for this.
>
> For the lock free, do we need to protect it with version counter? Imagine the
> following corner case:
> While the iterator read the key and data, there is a writer deleted, removed,
> and recycled the key-data pair, and write a new key and data into it. While the
> writer are writing, will the reader reads out wrong key/data, or mismatched
> key/data?
>
In the lock-free algorithm, the key-data is not 'freed' until the readers have completed all their references to the 'deleted' key-data. Hence, the writers will not be able to allocate the same key store index till the readers have stopped referring to the 'deleted' key-data.
I re-checked my ladder diagrams [1] and I could not find any issues.
[1] https://dpdkuserspace2018.sched.com/event/G44w/lock-free-read-write-concurrency-in-rtehash (PPT)
next prev parent reply other threads:[~2018-10-02 4:27 UTC|newest]
Thread overview: 107+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-06 17:09 [dpdk-dev] [PATCH v1 0/5] hash: add extendable bucket and partial-key hashing Yipeng Wang
2018-09-06 17:09 ` [dpdk-dev] [PATCH v1 1/5] test: fix bucket size in hash table perf test Yipeng Wang
2018-09-06 17:09 ` [dpdk-dev] [PATCH v1 2/5] test: more accurate hash table perf test output Yipeng Wang
2018-09-06 17:09 ` [dpdk-dev] [PATCH v1 3/5] hash: add extendable bucket feature Yipeng Wang
2018-09-06 17:09 ` [dpdk-dev] [PATCH v1 4/5] test: implement extendable bucket hash test Yipeng Wang
2018-09-06 17:09 ` [dpdk-dev] [PATCH v1 5/5] hash: use partial-key hashing Yipeng Wang
2018-09-21 17:17 ` [dpdk-dev] [PATCH v2 0/7] hash: add extendable bucket and partial key hashing Yipeng Wang
2018-09-21 17:17 ` [dpdk-dev] [PATCH v2 1/7] test/hash: fix bucket size in hash perf test Yipeng Wang
2018-09-26 10:04 ` Bruce Richardson
2018-09-27 3:39 ` Wang, Yipeng1
2018-09-27 4:23 ` Honnappa Nagarahalli
2018-09-29 0:31 ` Wang, Yipeng1
2018-09-21 17:17 ` [dpdk-dev] [PATCH v2 2/7] test/hash: more accurate hash perf test output Yipeng Wang
2018-09-26 10:07 ` Bruce Richardson
2018-09-21 17:17 ` [dpdk-dev] [PATCH v2 3/7] test/hash: fix rw test with non-consecutive cores Yipeng Wang
2018-09-26 11:02 ` Bruce Richardson
2018-09-27 3:40 ` Wang, Yipeng1
2018-09-26 11:13 ` Bruce Richardson
2018-09-21 17:17 ` [dpdk-dev] [PATCH v2 4/7] hash: fix unnecessary code Yipeng Wang
2018-09-26 12:55 ` Bruce Richardson
2018-09-21 17:17 ` [dpdk-dev] [PATCH v2 5/7] hash: add extendable bucket feature Yipeng Wang
2018-09-27 4:23 ` Honnappa Nagarahalli
2018-09-27 11:15 ` Bruce Richardson
2018-09-27 11:27 ` Ananyev, Konstantin
2018-09-27 12:27 ` Bruce Richardson
2018-09-27 12:33 ` Ananyev, Konstantin
2018-09-27 19:21 ` Honnappa Nagarahalli
2018-09-28 17:35 ` Wang, Yipeng1
2018-09-29 21:09 ` Honnappa Nagarahalli
2018-09-29 1:10 ` Wang, Yipeng1
2018-10-01 20:56 ` Honnappa Nagarahalli
2018-10-02 1:56 ` Wang, Yipeng1
2018-09-21 17:17 ` [dpdk-dev] [PATCH v2 6/7] test/hash: implement extendable bucket hash test Yipeng Wang
2018-09-27 4:24 ` Honnappa Nagarahalli
2018-09-29 0:50 ` Wang, Yipeng1
2018-09-21 17:17 ` [dpdk-dev] [PATCH v2 7/7] hash: use partial-key hashing Yipeng Wang
2018-09-27 4:24 ` Honnappa Nagarahalli
2018-09-29 0:55 ` Wang, Yipeng1
2018-09-26 12:57 ` [dpdk-dev] [PATCH v2 0/7] hash: add extendable bucket and partial key hashing Bruce Richardson
2018-09-27 3:41 ` Wang, Yipeng1
2018-09-27 4:23 ` Honnappa Nagarahalli
2018-09-29 0:46 ` Wang, Yipeng1
2018-09-26 12:54 ` [dpdk-dev] [PATCH v3 0/5] hash: fix multiple issues Yipeng Wang
2018-09-26 12:54 ` [dpdk-dev] [PATCH v3 1/5] test/hash: fix bucket size in hash perf test Yipeng Wang
2018-09-27 11:17 ` Bruce Richardson
2018-09-26 12:54 ` [dpdk-dev] [PATCH v3 2/5] test/hash: more accurate hash perf test output Yipeng Wang
2018-09-26 12:54 ` [dpdk-dev] [PATCH v3 3/5] test/hash: fix rw test with non-consecutive cores Yipeng Wang
2018-09-27 11:18 ` Bruce Richardson
2018-09-26 12:54 ` [dpdk-dev] [PATCH v3 4/5] test/hash: fix missing file in meson build file Yipeng Wang
2018-09-27 11:22 ` Bruce Richardson
2018-09-26 12:54 ` [dpdk-dev] [PATCH v3 5/5] hash: fix unused define Yipeng Wang
2018-09-28 14:11 ` [dpdk-dev] [PATCH v4 0/5] hash: fix multiple issues Yipeng Wang
2018-09-28 14:11 ` [dpdk-dev] [PATCH v4 1/5] test/hash: fix bucket size in hash perf test Yipeng Wang
2018-10-01 20:28 ` Honnappa Nagarahalli
2018-09-28 14:11 ` [dpdk-dev] [PATCH v4 2/5] test/hash: more accurate hash perf test output Yipeng Wang
2018-09-28 14:11 ` [dpdk-dev] [PATCH v4 3/5] test/hash: fix rw test with non-consecutive cores Yipeng Wang
2018-09-28 14:11 ` [dpdk-dev] [PATCH v4 4/5] test/hash: fix missing file in meson build file Yipeng Wang
2018-09-28 14:11 ` [dpdk-dev] [PATCH v4 5/5] hash: fix unused define Yipeng Wang
2018-10-25 22:04 ` [dpdk-dev] [PATCH v4 0/5] hash: fix multiple issues Thomas Monjalon
2018-09-26 20:26 ` [dpdk-dev] [PATCH v3 0/3] hash: add extendable bucket and partial key hashing Yipeng Wang
2018-09-26 20:26 ` [dpdk-dev] [PATCH v3 1/3] hash: add extendable bucket feature Yipeng Wang
2018-09-26 20:26 ` [dpdk-dev] [PATCH v3 2/3] test/hash: implement extendable bucket hash test Yipeng Wang
2018-09-26 20:26 ` [dpdk-dev] [PATCH v3 3/3] hash: use partial-key hashing Yipeng Wang
2018-09-28 17:23 ` [dpdk-dev] [PATCH v4 0/4] hash: add extendable bucket and partial key hashing Yipeng Wang
2018-09-28 17:23 ` [dpdk-dev] [PATCH v4 1/4] hash: fix race condition in iterate Yipeng Wang
2018-10-01 20:23 ` Honnappa Nagarahalli
2018-10-02 0:17 ` Wang, Yipeng1
2018-10-02 4:26 ` Honnappa Nagarahalli [this message]
2018-10-02 23:53 ` Wang, Yipeng1
2018-09-28 17:23 ` [dpdk-dev] [PATCH v4 2/4] hash: add extendable bucket feature Yipeng Wang
2018-10-02 3:58 ` Honnappa Nagarahalli
2018-10-02 23:39 ` Wang, Yipeng1
2018-10-03 4:37 ` Honnappa Nagarahalli
2018-10-03 15:08 ` Stephen Hemminger
2018-10-03 15:08 ` Stephen Hemminger
2018-10-03 16:53 ` Wang, Yipeng1
2018-10-03 17:59 ` Honnappa Nagarahalli
2018-10-04 1:22 ` Wang, Yipeng1
2018-09-28 17:23 ` [dpdk-dev] [PATCH v4 3/4] test/hash: implement extendable bucket hash test Yipeng Wang
2018-10-01 19:53 ` Honnappa Nagarahalli
2018-09-28 17:23 ` [dpdk-dev] [PATCH v4 4/4] hash: use partial-key hashing Yipeng Wang
2018-10-01 20:09 ` Honnappa Nagarahalli
2018-10-03 19:05 ` [dpdk-dev] [PATCH v4 0/4] hash: add extendable bucket and partial key hashing Dharmik Thakkar
2018-10-01 18:34 ` [dpdk-dev] [PATCH v5 " Yipeng Wang
2018-10-01 18:34 ` [dpdk-dev] [PATCH v5 1/4] hash: fix race condition in iterate Yipeng Wang
2018-10-02 17:26 ` Honnappa Nagarahalli
2018-10-01 18:35 ` [dpdk-dev] [PATCH v5 2/4] hash: add extendable bucket feature Yipeng Wang
2018-10-01 18:35 ` [dpdk-dev] [PATCH v5 3/4] test/hash: implement extendable bucket hash test Yipeng Wang
2018-10-01 18:35 ` [dpdk-dev] [PATCH v5 4/4] hash: use partial-key hashing Yipeng Wang
2018-10-02 20:52 ` Dharmik Thakkar
2018-10-03 0:43 ` Wang, Yipeng1
2018-10-03 19:10 ` [dpdk-dev] [PATCH v5 0/4] hash: add extendable bucket and partial key hashing Dharmik Thakkar
2018-10-04 0:36 ` Wang, Yipeng1
2018-10-04 16:35 ` [dpdk-dev] [PATCH v6 " Yipeng Wang
2018-10-04 16:35 ` [dpdk-dev] [PATCH v6 1/4] hash: fix race condition in iterate Yipeng Wang
2018-10-04 16:35 ` [dpdk-dev] [PATCH v6 2/4] hash: add extendable bucket feature Yipeng Wang
2018-10-04 16:35 ` [dpdk-dev] [PATCH v6 3/4] test/hash: implement extendable bucket hash test Yipeng Wang
2018-10-04 16:35 ` [dpdk-dev] [PATCH v6 4/4] hash: use partial-key hashing Yipeng Wang
2018-10-10 21:27 ` [dpdk-dev] [PATCH v7 0/4] hash: add extendable bucket and partial key hashing Yipeng Wang
2018-10-10 21:27 ` [dpdk-dev] [PATCH v7 1/4] hash: fix race condition in iterate Yipeng Wang
2018-10-10 21:27 ` [dpdk-dev] [PATCH v7 2/4] hash: add extendable bucket feature Yipeng Wang
2018-10-10 21:27 ` [dpdk-dev] [PATCH v7 3/4] test/hash: implement extendable bucket hash test Yipeng Wang
2018-10-10 21:27 ` [dpdk-dev] [PATCH v7 4/4] hash: use partial-key hashing Yipeng Wang
2018-10-16 18:47 ` [dpdk-dev] [PATCH] doc: update release note for hash library Yipeng Wang
2018-10-17 20:09 ` Honnappa Nagarahalli
2018-10-25 18:45 ` Wang, Yipeng1
2018-10-25 23:07 ` Thomas Monjalon
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