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From: "Van Haaren, Harry" <harry.van.haaren@intel.com>
To: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"phil.yang@arm.com" <phil.yang@arm.com>
Cc: "thomas@monjalon.net" <thomas@monjalon.net>,
	"david.marchand@redhat.com" <david.marchand@redhat.com>,
	"Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
	"jerinj@marvell.com" <jerinj@marvell.com>,
	"hemant.agrawal@nxp.com" <hemant.agrawal@nxp.com>,
	"Eads, Gage" <gage.eads@intel.com>,
	"Richardson, Bruce" <bruce.richardson@intel.com>,
	"nd@arm.com" <nd@arm.com>, "stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [dpdk-stable] [PATCH v3 2/6] service: identify service running on another core correctly
Date: Tue, 5 May 2020 14:48:24 +0000	[thread overview]
Message-ID: <BYAPR11MB31432F7C43C6C48885ADFB91D7A70@BYAPR11MB3143.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20200502000245.11071-3-honnappa.nagarahalli@arm.com>

> -----Original Message-----
> From: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Sent: Saturday, May 2, 2020 1:03 AM
> To: dev@dpdk.org; phil.yang@arm.com; Van Haaren, Harry
> <harry.van.haaren@intel.com>
> Cc: thomas@monjalon.net; david.marchand@redhat.com; Ananyev, Konstantin
> <konstantin.ananyev@intel.com>; jerinj@marvell.com;
> hemant.agrawal@nxp.com; Eads, Gage <gage.eads@intel.com>; Richardson,
> Bruce <bruce.richardson@intel.com>; honnappa.nagarahalli@arm.com;
> nd@arm.com; stable@dpdk.org
> Subject: [PATCH v3 2/6] service: identify service running on another core
> correctly
>
> The logic to identify if the MT unsafe service is running on another
> core can return -EBUSY spuriously. In such cases, running the service
> becomes costlier than using atomic operations. Assume that the
> application passes the right parameters and reduces the number of
> instructions for all cases.
> 
> Cc: stable@dpdk.org
> Fixes: 8d39d3e237c2 ("service: fix race in service on app lcore function")

Add "fix" to the title, suggestion:
service: fix identification of service running on other lcore

> Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Reviewed-by: Phil Yang <phil.yang@arm.com>

I believe there may be some optimizations we can apply after this patchset
as the "num_mapped_cores" variable is no longer used in a significant way 
for the atomic selection, however lets leave that optimization outside
of 20.05 scope.

With title (see above) & comment (see below) updated.
Acked-by: Harry van Haaren <harry.van.haaren@intel.com>

> ---
<snip some diff>
> @@ -412,24 +412,14 @@ rte_service_run_iter_on_app_lcore(uint32_t id,
> uint32_t serialize_mt_unsafe)
> 
>  	SERVICE_VALID_GET_OR_ERR_RET(id, s, -EINVAL);
> 
> -	/* Atomically add this core to the mapped cores first, then examine if
> -	 * we can run the service. This avoids a race condition between
> -	 * checking the value, and atomically adding to the mapped count.
> +	/* Increment num_mapped_cores to indicate that the service
> +	 * is running on a core.
>  	 */
> -	if (serialize_mt_unsafe)
> -		rte_atomic32_inc(&s->num_mapped_cores);
> +	rte_atomic32_inc(&s->num_mapped_cores);

The comment for the added lines here are a little confusing to me,
the "num_mapped_cores" does not indicate that the service "is running on a core",
it indicates the number of mapped lcores to that service. Suggestion below?

/* Increment num_mapped_cores to reflect that this core is
 * now mapped capable of running the service.
 */

> -	if (service_mt_safe(s) == 0 &&
> -			rte_atomic32_read(&s->num_mapped_cores) > 1) {
> -		if (serialize_mt_unsafe)
> -			rte_atomic32_dec(&s->num_mapped_cores);
> -		return -EBUSY;
> -	}
> -
> -	int ret = service_run(id, cs, UINT64_MAX, s);
> +	int ret = service_run(id, cs, UINT64_MAX, s, serialize_mt_unsafe);

<snip rest of diff>


  reply	other threads:[~2020-05-05 14:48 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1583862551-2049-1-git-send-email-phil.yang@arm.com>
2020-03-10 17:49 ` [dpdk-stable] [PATCH 05/10] service: remove rte prefix from static functions Phil Yang
2020-03-10 17:49 ` [dpdk-stable] [PATCH 06/10] service: remove redundant code Phil Yang
2020-03-10 17:49 ` [dpdk-stable] [PATCH 07/10] service: avoid race condition for MT unsafe service Phil Yang
2020-03-10 17:49 ` [dpdk-stable] [PATCH 08/10] service: identify service running on another core correctly Phil Yang
     [not found] ` <1583993624-20446-1-git-send-email-phil.yang@arm.com>
2020-03-12  6:13   ` [dpdk-stable] [PATCH v2 05/10] service: remove rte prefix from static functions Phil Yang
2020-03-12  6:13   ` [dpdk-stable] [PATCH v2 06/10] service: remove redundant code Phil Yang
2020-03-12  6:13   ` [dpdk-stable] [PATCH v2 07/10] service: avoid race condition for MT unsafe service Phil Yang
2020-03-12  6:13   ` [dpdk-stable] [PATCH v2 08/10] service: identify service running on another core correctly Phil Yang
     [not found] ` <1583999071-22872-1-git-send-email-phil.yang@arm.com>
2020-03-12  7:44   ` [dpdk-stable] [PATCH v2 05/10] service: remove rte prefix from static functions Phil Yang
2020-03-12  7:44   ` [dpdk-stable] [PATCH v2 06/10] service: remove redundant code Phil Yang
2020-03-12  7:44   ` [dpdk-stable] [PATCH v2 07/10] service: avoid race condition for MT unsafe service Phil Yang
2020-03-12  7:44   ` [dpdk-stable] [PATCH v2 08/10] service: identify service running on another core correctly Phil Yang
     [not found]   ` <1584407863-774-1-git-send-email-phil.yang@arm.com>
2020-03-17  1:17     ` [dpdk-stable] [PATCH v3 07/12] service: remove rte prefix from static functions Phil Yang
2020-04-03 11:57       ` Van Haaren, Harry
2020-04-08 10:14         ` Phil Yang
2020-04-08 10:36           ` Van Haaren, Harry
2020-04-08 10:49             ` Phil Yang
2020-04-05 21:35       ` Honnappa Nagarahalli
2020-04-08 10:14         ` Phil Yang
     [not found]       ` <1587659482-27133-1-git-send-email-phil.yang@arm.com>
2020-04-23 16:31         ` [dpdk-stable] [PATCH v2 1/6] service: fix race condition for MT unsafe service Phil Yang
2020-04-29 16:51           ` Van Haaren, Harry
2020-04-29 22:48             ` Honnappa Nagarahalli
2020-05-01 14:21               ` Van Haaren, Harry
2020-05-01 14:56                 ` Honnappa Nagarahalli
2020-05-01 17:51                   ` Van Haaren, Harry
2020-04-23 16:31         ` [dpdk-stable] [PATCH v2 2/6] service: identify service running on another core correctly Phil Yang
     [not found]         ` <20200502000245.11071-1-honnappa.nagarahalli@arm.com>
2020-05-02  0:02           ` [dpdk-stable] [PATCH v3 1/6] service: fix race condition for MT unsafe service Honnappa Nagarahalli
2020-05-05 14:48             ` Van Haaren, Harry
2020-05-02  0:02           ` [dpdk-stable] [PATCH v3 2/6] service: identify service running on another core correctly Honnappa Nagarahalli
2020-05-05 14:48             ` Van Haaren, Harry [this message]
     [not found]         ` <20200505211732.25291-1-honnappa.nagarahalli@arm.com>
2020-05-05 21:17           ` [dpdk-stable] [PATCH v4 1/6] service: fix race condition for MT unsafe service Honnappa Nagarahalli
2020-05-05 21:17           ` [dpdk-stable] [PATCH v4 2/6] service: fix identification of service running on other lcore Honnappa Nagarahalli
     [not found]           ` <1588760683-11027-1-git-send-email-phil.yang@arm.com>
2020-05-06 10:24             ` [dpdk-stable] [PATCH v5 1/6] service: fix race condition for MT unsafe service Phil Yang
2020-05-06 10:24             ` [dpdk-stable] [PATCH v5 2/6] service: fix identification of service running on other lcore Phil Yang
     [not found]             ` <1588778884-13047-1-git-send-email-phil.yang@arm.com>
2020-05-06 15:27               ` [dpdk-stable] [PATCH v6 1/6] service: fix race condition for MT unsafe service Phil Yang
2020-05-06 15:28               ` [dpdk-stable] [PATCH v6 2/6] service: fix identification of service running on other lcore Phil Yang
2020-03-17  1:17     ` [dpdk-stable] [PATCH v3 08/12] service: remove redundant code Phil Yang
2020-04-03 11:58       ` Van Haaren, Harry
2020-04-05 18:35         ` Honnappa Nagarahalli
2020-04-08 10:15           ` Phil Yang
2020-03-17  1:17     ` [dpdk-stable] [PATCH v3 09/12] service: avoid race condition for MT unsafe service Phil Yang
2020-04-03 11:58       ` Van Haaren, Harry
2020-04-04 18:03         ` Honnappa Nagarahalli
2020-04-08 18:05           ` Van Haaren, Harry
2020-04-09  1:31             ` Honnappa Nagarahalli
2020-04-09 16:46               ` Van Haaren, Harry
2020-04-18  6:21                 ` Honnappa Nagarahalli
2020-04-21 17:43                   ` Van Haaren, Harry
2020-03-17  1:17     ` [dpdk-stable] [PATCH v3 10/12] service: identify service running on another core correctly Phil Yang
2020-04-03 11:58       ` Van Haaren, Harry
2020-04-05  2:43         ` Honnappa Nagarahalli

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