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From: "Carrillo, Erik G" <erik.g.carrillo@intel.com>
To: Phil Yang <phil.yang@arm.com>, "dev@dpdk.org" <dev@dpdk.org>
Cc: "drc@linux.vnet.ibm.com" <drc@linux.vnet.ibm.com>,
	"honnappa.nagarahalli@arm.com" <honnappa.nagarahalli@arm.com>,
	"ruifeng.wang@arm.com" <ruifeng.wang@arm.com>,
	"dharmik.thakkar@arm.com" <dharmik.thakkar@arm.com>,
	"nd@arm.com" <nd@arm.com>, "stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH 1/3] eventdev: fix race condition on timer list counter
Date: Thu, 18 Jun 2020 15:17:44 +0000	[thread overview]
Message-ID: <CY4PR1101MB2118653CE0272DB20268C2B9B99B0@CY4PR1101MB2118.namprd11.prod.outlook.com> (raw)
In-Reply-To: <1591960798-24024-1-git-send-email-phil.yang@arm.com>

Hi Phil,

Good catch - thanks for the fix.   I've commented in-line:

> -----Original Message-----
> From: Phil Yang <phil.yang@arm.com>
> Sent: Friday, June 12, 2020 6:20 AM
> To: dev@dpdk.org; Carrillo, Erik G <erik.g.carrillo@intel.com>
> Cc: drc@linux.vnet.ibm.com; honnappa.nagarahalli@arm.com;
> ruifeng.wang@arm.com; dharmik.thakkar@arm.com; nd@arm.com;
> stable@dpdk.org
> Subject: [PATCH 1/3] eventdev: fix race condition on timer list counter
> 
> The n_poll_lcores counter and poll_lcore array are shared between lcores
> and the update of these variables are out of the protection of spinlock on
> each lcore timer list. The read-modify-write operations of the counter are
> not atomic, so it has the potential of race condition between lcores.
> 
> Use c11 atomics with RELAXED ordering to prevent confliction.
> 
> Fixes: cc7b73ea9e3b ("eventdev: add new software timer adapter")
> Cc: erik.g.carrillo@intel.com
> Cc: stable@dpdk.org
> 
> Signed-off-by: Phil Yang <phil.yang@arm.com>
> Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
>  lib/librte_eventdev/rte_event_timer_adapter.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/librte_eventdev/rte_event_timer_adapter.c
> b/lib/librte_eventdev/rte_event_timer_adapter.c
> index 005459f..6a0e283 100644
> --- a/lib/librte_eventdev/rte_event_timer_adapter.c
> +++ b/lib/librte_eventdev/rte_event_timer_adapter.c
> @@ -583,6 +583,7 @@ swtim_callback(struct rte_timer *tim)
>  	uint16_t nb_evs_invalid = 0;
>  	uint64_t opaque;
>  	int ret;
> +	int n_lcores;
> 
>  	opaque = evtim->impl_opaque[1];
>  	adapter = (struct rte_event_timer_adapter *)(uintptr_t)opaque;
> @@ -605,8 +606,12 @@ swtim_callback(struct rte_timer *tim)
>  				      "with immediate expiry value");
>  		}
> 
> -		if (unlikely(rte_atomic16_test_and_set(&sw-
> >in_use[lcore].v)))
> -			sw->poll_lcores[sw->n_poll_lcores++] = lcore;
> +		if (unlikely(rte_atomic16_test_and_set(&sw-
> >in_use[lcore].v))) {
> +			n_lcores = __atomic_fetch_add(&sw->n_poll_lcores,
> 1,
> +						__ATOMIC_RELAXED);

Just a nit, but let's align the continued line with the opening parentheses in
this location and below.  With these changes:

Acked-by: Erik Gabriel Carrillo <erik.g.carrillo@intel.com>

> +			__atomic_store_n(&sw->poll_lcores[n_lcores],
> lcore,
> +						__ATOMIC_RELAXED);
> +		}
>  	} else {
>  		EVTIM_BUF_LOG_DBG("buffered an event timer expiry
> event");
> 
> @@ -1011,6 +1016,7 @@ __swtim_arm_burst(const struct
> rte_event_timer_adapter *adapter,
>  	uint32_t lcore_id = rte_lcore_id();
>  	struct rte_timer *tim, *tims[nb_evtims];
>  	uint64_t cycles;
> +	int n_lcores;
> 
>  #ifdef RTE_LIBRTE_EVENTDEV_DEBUG
>  	/* Check that the service is running. */ @@ -1033,8 +1039,10 @@
> __swtim_arm_burst(const struct rte_event_timer_adapter *adapter,
>  	if (unlikely(rte_atomic16_test_and_set(&sw->in_use[lcore_id].v))) {
>  		EVTIM_LOG_DBG("Adding lcore id = %u to list of lcores to
> poll",
>  			      lcore_id);
> -		sw->poll_lcores[sw->n_poll_lcores] = lcore_id;
> -		++sw->n_poll_lcores;
> +		n_lcores = __atomic_fetch_add(&sw->n_poll_lcores, 1,
> +						__ATOMIC_RELAXED);
> +		__atomic_store_n(&sw->poll_lcores[n_lcores], lcore_id,
> +						__ATOMIC_RELAXED);
>  	}
> 
>  	ret = rte_mempool_get_bulk(sw->tim_pool, (void **)tims,
> --
> 2.7.4


  parent reply	other threads:[~2020-06-18 15:17 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-12 11:19 Phil Yang
2020-06-12 11:19 ` [dpdk-dev] [PATCH 2/3] eventdev: use c11 atomics for lcore timer armed flag Phil Yang
2020-06-23 21:01   ` Carrillo, Erik G
2020-06-28 16:12     ` Phil Yang
2020-06-23 21:20   ` Stephen Hemminger
2020-06-23 21:31     ` Carrillo, Erik G
2020-06-28 16:32       ` Phil Yang
2020-06-12 11:19 ` [dpdk-dev] [PATCH 3/3] eventdev: relax smp barriers with c11 atomics Phil Yang
2020-06-22 10:12   ` Phil Yang
2020-06-23 19:38     ` Carrillo, Erik G
2020-06-28 17:33       ` Phil Yang
2020-06-29 18:07         ` Carrillo, Erik G
2020-06-18 15:17 ` Carrillo, Erik G [this message]
2020-06-18 18:25   ` [dpdk-dev] [PATCH 1/3] eventdev: fix race condition on timer list counter Honnappa Nagarahalli
2020-06-22  9:48     ` Phil Yang
2020-07-01 11:22       ` Jerin Jacob
2020-07-02  3:28         ` Phil Yang
2020-07-02  3:26     ` Phil Yang
2020-07-02  3:56       ` Honnappa Nagarahalli
2020-07-02 21:15         ` Carrillo, Erik G
2020-07-02 21:30           ` Honnappa Nagarahalli
2020-06-22  9:09   ` Phil Yang
2020-07-02  5:26 ` [dpdk-dev] [PATCH v2 1/4] " Phil Yang
2020-07-02  5:26   ` [dpdk-dev] [PATCH v2 2/4] eventdev: use c11 atomics for lcore timer armed flag Phil Yang
2020-07-02 20:21     ` Carrillo, Erik G
2020-07-02  5:26   ` [dpdk-dev] [PATCH v2 3/4] eventdev: remove redundant code Phil Yang
2020-07-03  3:35     ` Dharmik Thakkar
2020-07-02  5:26   ` [dpdk-dev] [PATCH v2 4/4] eventdev: relax smp barriers with c11 atomics Phil Yang
2020-07-02 20:30     ` Carrillo, Erik G
2020-07-03 10:50       ` Jerin Jacob
2020-07-06 10:04     ` Thomas Monjalon
2020-07-06 15:32       ` Phil Yang
2020-07-06 15:40         ` Thomas Monjalon
2020-07-07 11:13   ` [dpdk-dev] [PATCH v3 1/4] eventdev: fix race condition on timer list counter Phil Yang
2020-07-07 11:13     ` [dpdk-dev] [PATCH v3 2/4] eventdev: use C11 atomics for lcore timer armed flag Phil Yang
2020-07-07 11:13     ` [dpdk-dev] [PATCH v3 3/4] eventdev: remove redundant code Phil Yang
2020-07-07 11:13     ` [dpdk-dev] [PATCH v3 4/4] eventdev: relax smp barriers with C11 atomics Phil Yang
2020-07-07 14:29       ` Jerin Jacob
2020-07-07 15:56         ` Phil Yang
2020-07-07 15:54     ` [dpdk-dev] [PATCH v4 1/4] eventdev: fix race condition on timer list counter Phil Yang
2020-07-07 15:54       ` [dpdk-dev] [PATCH v4 2/4] eventdev: use C11 atomics for lcore timer armed flag Phil Yang
2020-07-07 15:54       ` [dpdk-dev] [PATCH v4 3/4] eventdev: remove redundant code Phil Yang
2020-07-07 15:54       ` [dpdk-dev] [PATCH v4 4/4] eventdev: relax smp barriers with C11 atomics Phil Yang
2020-07-08 13:30       ` [dpdk-dev] [PATCH v4 1/4] eventdev: fix race condition on timer list counter Jerin Jacob
2020-07-08 15:01         ` Thomas Monjalon

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