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From: "Wang, Yipeng1" <yipeng1.wang@intel.com>
To: Qiaobin Fu <qiaobinf@bu.edu>,
	"Richardson, Bruce" <bruce.richardson@intel.com>,
	"De Lara Guarch, Pablo" <pablo.de.lara.guarch@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	"doucette@bu.edu" <doucette@bu.edu>,
	"Wiles, Keith" <keith.wiles@intel.com>,
	"Gobriel, Sameh" <sameh.gobriel@intel.com>,
	"Tai, Charlie" <charlie.tai@intel.com>,
	"stephen@networkplumber.org" <stephen@networkplumber.org>,
	"nd@arm.com" <nd@arm.com>,
	"honnappa.nagarahalli@arm.com" <honnappa.nagarahalli@arm.com>,
	"michel@digirati.com.br" <michel@digirati.com.br>
Subject: Re: [dpdk-dev] [PATCH v4 1/2] hash table: fix a bug in rte_hash_iterate()
Date: Wed, 10 Oct 2018 01:55:28 +0000
Message-ID: <D2C4A16CA39F7F4E8E384D204491D7A6614EE328@FMSMSX151.amr.corp.intel.com> (raw)
In-Reply-To: <20181009192907.85650-1-qiaobinf@bu.edu>

Hi Qiaobin,

This patch: http://patchwork.dpdk.org/patch/46105/ covers the bug.  Honnappa suggested a fix that would work well for the lock free implementation as well.

>-----Original Message-----
>From: Qiaobin Fu [mailto:qiaobinf@bu.edu]
>Sent: Tuesday, October 9, 2018 12:29 PM
>To: Richardson, Bruce <bruce.richardson@intel.com>; De Lara Guarch, Pablo <pablo.de.lara.guarch@intel.com>
>Cc: dev@dpdk.org; doucette@bu.edu; Wiles, Keith <keith.wiles@intel.com>; Gobriel, Sameh <sameh.gobriel@intel.com>; Tai, Charlie
><charlie.tai@intel.com>; stephen@networkplumber.org; nd@arm.com; honnappa.nagarahalli@arm.com; Wang, Yipeng1
><yipeng1.wang@intel.com>; michel@digirati.com.br; qiaobinf@bu.edu
>Subject: [PATCH v4 1/2] hash table: fix a bug in rte_hash_iterate()
>
>In current implementation of rte_hash_iterate(), it
>tries to obtain the lock after the while loop. However,
>this may lead to a bug. Notice the following racing condition:
>
>1. The while loop above finishes because it finds
>   a not empty slot. But it does so without a lock.
>2. Then we get the lock.
>3. The position that was once not empty is now empty.
>   BUG because next_key is invalid.
>
>This patch fixes this small bug.
>
>Signed-off-by: Qiaobin Fu <qiaobinf@bu.edu>
>Reviewed-by: Michel Machado <michel@digirati.com.br>
>---
> lib/librte_hash/rte_cuckoo_hash.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
>diff --git a/lib/librte_hash/rte_cuckoo_hash.c b/lib/librte_hash/rte_cuckoo_hash.c
>index f7b86c8c9..a3e76684d 100644
>--- a/lib/librte_hash/rte_cuckoo_hash.c
>+++ b/lib/librte_hash/rte_cuckoo_hash.c
>@@ -1317,16 +1317,18 @@ 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);
> 	/* 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];
> 	next_key = (struct rte_hash_key *) ((char *)h->key_store +
>--
>2.17.1

      parent reply	other threads:[~2018-10-10  2:01 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-31 16:51 [dpdk-dev] [PATCH v3] hash table: add an iterator over conflicting entries Qiaobin Fu
2018-08-31 22:53 ` Gaëtan Rivet
2018-09-04 18:46   ` Michel Machado
2018-09-02 22:05 ` Honnappa Nagarahalli
2018-09-04 19:36   ` Michel Machado
2018-09-05 22:13     ` Honnappa Nagarahalli
2018-09-06 14:28       ` Michel Machado
2018-09-12 20:37         ` Honnappa Nagarahalli
2018-09-20 19:50           ` Michel Machado
2018-09-04 18:55 ` Wang, Yipeng1
2018-09-04 19:07   ` Michel Machado
2018-09-04 19:51     ` Wang, Yipeng1
2018-09-04 20:26       ` Michel Machado
2018-09-04 20:57         ` Wang, Yipeng1
2018-09-05 17:52           ` Michel Machado
2018-09-05 20:27             ` Wang, Yipeng1
2018-09-06 13:34               ` Michel Machado
2018-10-09 19:29 ` [dpdk-dev] [PATCH v4 1/2] hash table: fix a bug in rte_hash_iterate() Qiaobin Fu
2018-10-09 19:29   ` [dpdk-dev] [PATCH v4 2/2] hash table: add an iterator over conflicting entries Qiaobin Fu
2018-10-10  2:54     ` Wang, Yipeng1
2018-10-10  1:55   ` Wang, Yipeng1 [this message]

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