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From: Thomas Monjalon <thomas@monjalon.net>
To: Jia He <hejianet@gmail.com>, Jia He <jia.he@hxt-semitech.com>
Cc: stable@dpdk.org, jerin.jacob@caviumnetworks.com, dev@dpdk.org,
	olivier.matz@6wind.com, konstantin.ananyev@intel.com,
	bruce.richardson@intel.com, jianbo.liu@arm.com,
	hemant.agrawal@nxp.com, jie2.liu@hxt-semitech.com,
	bing.zhao@hxt-semitech.com
Subject: Re: [dpdk-dev] [dpdk-stable] [PATCH v6] ring: guarantee load/load order in enqueue and dequeue
Date: Sun, 12 Nov 2017 18:51:37 +0100	[thread overview]
Message-ID: <3554910.3QoyqmBB3R@xps> (raw)
In-Reply-To: <1510284642-7442-2-git-send-email-hejianet@gmail.com>

10/11/2017 04:30, Jia He:
> We watched a rte panic of mbuf_autotest in our qualcomm arm64 server
> (Amberwing).
> 
> Root cause:
> In __rte_ring_move_cons_head()
> ...
>         do {
>                 /* Restore n as it may change every loop */
>                 n = max;
> 
>                 *old_head = r->cons.head;                //1st load
>                 const uint32_t prod_tail = r->prod.tail; //2nd load
> 
> In weak memory order architectures(powerpc,arm), the 2nd load might be
> reodered before the 1st load, that makes *entries is bigger than we wanted.
> This nasty reording messed enque/deque up.
> 
> cpu1(producer)          cpu2(consumer)          cpu3(consumer)
>                         load r->prod.tail
> in enqueue:
> load r->cons.tail
> load r->prod.head
> 
> store r->prod.tail
> 
>                                                 load r->cons.head
>                                                 load r->prod.tail
>                                                 ...
>                                                 store r->cons.{head,tail}
>                         load r->cons.head
> 
> Then, r->cons.head will be bigger than prod_tail, then make *entries very
> big and the consumer will go forward incorrectly.
> 
> After this patch, the old cons.head will be recaculated after failure of
> rte_atomic32_cmpset
> 
> There is no such issue on X86, because X86 is strong memory order model.
> But rte_smp_rmb() doesn't have impact on runtime performance on X86, so
> keep the same code without architectures specific concerns.
> 
> Signed-off-by: Jia He <jia.he@hxt-semitech.com>
> Signed-off-by: jie2.liu@hxt-semitech.com
> Signed-off-by: bing.zhao@hxt-semitech.com
> Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> Acked-by: Jianbo Liu <jianbo.liu@arm.com>
> Cc: stable@dpdk.org

Applied, thanks

  reply	other threads:[~2017-11-12 17:51 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1510118764-29697-1-git-send-email-hejianet@gmail.com>
2017-11-08  9:54 ` [dpdk-dev] [PATCH v4 0/4] fix race condition in enqueue/dequeue because of cpu reorder Jia He
2017-11-08  9:54   ` [dpdk-dev] [PATCH v4 1/4] eal/arm64: remove the braces {} for dmb() and dsb() Jia He
2017-11-08  9:54   ` [dpdk-dev] [PATCH v4 2/4] ring: guarantee load/load order in enqueue and dequeue Jia He
2017-11-08  9:54   ` [dpdk-dev] [PATCH v4 3/4] ring: introduce new header file to include common functions Jia He
2017-11-08  9:54   ` [dpdk-dev] [PATCH v4 4/4] ring: introduce new header file to support C11 memory model Jia He
2017-11-08 12:15   ` [dpdk-dev] [PATCH v4 0/4] fix race condition in enqueue/dequeue because of cpu reorder Bruce Richardson
2017-11-08 15:11     ` Jia He
2017-11-08 16:29       ` Jerin Jacob
2017-11-08 18:36       ` Ananyev, Konstantin
     [not found]       ` <2459a535-920e-9ac5-2f46-1d1dd00e275b@gmail.com>
2017-11-24  9:24         ` Bruce Richardson
2017-11-10  1:51 ` [dpdk-dev] [PATCH v5 0/1] " Jia He
2017-11-10  1:51   ` [dpdk-dev] [PATCH v5 1/1] ring: guarantee load/load order in enqueue and dequeue Jia He
2017-11-10  2:46     ` Jerin Jacob
2017-11-10  3:12       ` Jianbo Liu
2017-11-10  9:59     ` Ananyev, Konstantin
2017-11-10  3:30   ` [dpdk-dev] [PATCH v6] " Jia He
2017-11-10  3:30     ` [dpdk-dev] [PATCH v6] ring: " Jia He
2017-11-12 17:51       ` Thomas Monjalon [this message]
2017-11-10  5:23   ` [dpdk-dev] [PATCH v5 0/3] support c11 memory model barrier in librte_ring Jia He
2017-11-10  5:23     ` [dpdk-dev] [PATCH v5 1/3] eal/arm64: remove the braces {} for dmb() and dsb() Jia He
2017-11-10  5:23     ` [dpdk-dev] [PATCH v5 2/3] ring: introduce new header file to include common functions Jia He
2017-11-10  5:23     ` [dpdk-dev] [PATCH v6 3/3] ring: introduce new header file to support C11 memory model Jia He
2017-11-27  2:00     ` [dpdk-dev] [PATCH V6 0/3] support c11 memory model barrier in librte_ring Jia He
2017-11-27  2:00       ` [dpdk-dev] [PATCH V6 1/3] eal/arm64: remove the braces {} for dmb() and dsb() Jia He
2017-12-03 11:11         ` Jerin Jacob
2017-11-27  2:00       ` [dpdk-dev] [PATCH V6 2/3] ring: introduce new header file to include common functions Jia He
2017-12-03 12:13         ` Jerin Jacob
2017-11-27  2:00       ` [dpdk-dev] [PATCH V6 3/3] ring: introduce new header file to support C11 memory model Jia He
2017-12-03 12:14         ` Jerin Jacob
2017-12-04  1:50       ` [dpdk-dev] [PATCH V7 0/3] support c11 memory model barrier in librte_ring Jia He
2017-12-04  1:50         ` [dpdk-dev] [PATCH V7 1/3] eal/arm64: remove the braces {} for dmb() and dsb() Jia He
2017-12-04  1:50         ` [dpdk-dev] [PATCH V7 2/3] ring: introduce new header file to include common functions Jia He
2018-01-12 17:09           ` Thomas Monjalon
2018-01-16  2:06             ` Jia He
2018-01-16 15:19           ` Olivier Matz
2017-12-04  1:50         ` [dpdk-dev] [PATCH V7 3/3] ring: introduce new header file to support C11 memory model Jia He
2017-12-04  8:05           ` Jianbo Liu
2018-01-12 17:18           ` Thomas Monjalon
2018-01-16 15:18           ` Olivier Matz

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