Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
From:   "Zhang, Qiang1" <qiang1.zhang@intel.com>
To:     "paulmck@kernel.org" <paulmck@kernel.org>
CC:     "frederic@kernel.org" <frederic@kernel.org>,
        "rcu@vger.kernel.org" <rcu@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] rcu: Direct boosting gp_tasks for strict grace periods
Thread-Topic: [PATCH] rcu: Direct boosting gp_tasks for strict grace periods
Thread-Index: AQHYZmJsqZZOz0NYwkqRvRtT9o+4C60b/q+AgAC5l6A=
Date:   Fri, 13 May 2022 13:17:16 +0000
Message-ID: <PH0PR11MB588012EC5E5DFD3FFDA49401DACA9@PH0PR11MB5880.namprd11.prod.outlook.com>
References: <20220513004256.465233-1-qiang1.zhang@intel.com>
 <20220513010651.GD1790663@paulmck-ThinkPad-P17-Gen-1>
In-Reply-To: <20220513010651.GD1790663@paulmck-ThinkPad-P17-Gen-1>
Accept-Language: en-US
Content-Language: en-US
dlp-product: dlpe-windows
dlp-version: 11.6.401.20
dlp-reaction: no-action
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?lm7O0h47nM3L6A8TmtuafZcmPTDECx6S2kTe3A4km8Mvhkg1f28uvmpWfEbg?=
 =?us-ascii?Q?Bh/E60qp/os5OTXH2pufrWrFjwx47+tPi5SFdwV6YQKVJ4Ku+DOiNOxPZ/+R?=
 =?us-ascii?Q?nqQOpEImNO0EYOVuRgPRvs6vN4NSgsmdfIZ8UmsNTu5u1LEoo9R+5OV/8Gzh?=
 =?us-ascii?Q?kDyeElJjhMzrK4pIeS+4c89I+jXO9Y8pfcrVRtvZI/4/HKgQJ115BfKsRX3Z?=
 =?us-ascii?Q?YD5dERX+8F6nqk2g2QFhXbx1xbi6vG9o9lsVJV+flKB+dVpyioDIG27a5Vjx?=
 =?us-ascii?Q?wrLQVOa/sSS/u3DNua1TofM/tYsEKe11acrQA/rwCIngNL3aryFMX9731cgr?=
 =?us-ascii?Q?MH9rb0nw+cyX1huWSIFsl2I1vnzVgANSeS01aWSwuiMB7zCVXbdN0Q9PQBOP?=
 =?us-ascii?Q?9f8xgt9FJFTOsJZ8xNKn01O54B6+oyeVbnb2mUpGopPjQKknTmvZRzUZEvUO?=
 =?us-ascii?Q?zGs6lVjXTSaGD6zFCGzDOwA39W2o46+5zVgaHOUPE0VQnXIB69fw5/hDsfrc?=
 =?us-ascii?Q?IIe4pIpwadbuSEBFY4eToIRs054JzEGaYfUmKKVaA2+AZB1Mupzic6vivf3n?=
 =?us-ascii?Q?caQylc/ANmTnaYq37QzCYpYr7gP7zf5CR4hW0mi0gltdcL7rfbGSZNa/d+B0?=
 =?us-ascii?Q?YFqx0ypFO0xhl0tnKJGjhiuI0HtVkSktwPvnEdVx65zg4SwYKVr9L+5oACWJ?=
 =?us-ascii?Q?mnUhJo17+6c9tFaiKNDyrh3aMHGKM5KGqrpQOCPoda3g48UzVbmcdxUpj/xW?=
 =?us-ascii?Q?pcIvsMQ8dOTEEL3nN9Yz3z6w3x5LwYt3YbJsdQcil3Xu1+A6qxtMb3N0555P?=
 =?us-ascii?Q?BBJ3YYnXBwXHw4U65BPS780yjN3jpfcpA84CrI6u5fN3+QA4LBYnmY8etKwW?=
 =?us-ascii?Q?lFo/KGBArVMD8/vu7/+h+uIdYxzd3l9hST0HaNHIhkCYzYTxsRy1HItcqSsH?=
 =?us-ascii?Q?PWJhD9sqSrXoxmueYQi1gc1HfvLDh2o75kMCELJZX11ON3u5tQ8ALYE6XWYw?=
 =?us-ascii?Q?Maq1lQX/t0aCKUd+r9ABnlf2jZyxY2/qre60gDkzIotc8RHZU4zU1hCP77/B?=
 =?us-ascii?Q?qfkvSEdIfaHWFW9l/YuFTrbkP3Om2J5tpzYicHNAFGba025Kb0ihQk/AfRvu?=
 =?us-ascii?Q?o1oSgERPtoTI1rI+Z15aP8HHTZSOIQ527u5Klcp57WnV3IiztFlWwJQ6ofrn?=
 =?us-ascii?Q?38MPlh/atFOHkroxDAioWhtE278h5jU6Jl63OrFJyOA/X3JW8ZQ9H02+gaz7?=
 =?us-ascii?Q?4bIvo8C8l3EQ0PVQoNTJFtSdI3sd/YyHY+SJjt1ovPm4waG/y08vyviZhDvL?=
 =?us-ascii?Q?i9BcdlcBV2eeddqY629BbsqGQyIsgqnNEPPlr2BVpT5eup0UqLlLPIutIAww?=
 =?us-ascii?Q?KCXHLL5aPvTqpN2PjoAQk9UswydXdRNW4bsDpWyui9hEZTEW+PD/rCY355eb?=
 =?us-ascii?Q?TmVUCScm+A3WGnfqV4CeIkHi+uDFXTjyCoizoDdEgCWc0fduViIJoZC7RUuu?=
 =?us-ascii?Q?RhgvKstnMdXFjSsZUVKRasNlIdtF4r2UKzSvruova7IDPu09VNR9UAYRMzu+?=
 =?us-ascii?Q?s0FVxtPuKRw1Z46elAtx8Kn5D0hhPO0VHywuDwrgSGv1pPx/Rk6KJEmIwhdx?=
 =?us-ascii?Q?sfrP6gIidMew5HwIYr128/pllJevR0LX9xoDT1TC3IpgsnHysV4AXh+qXook?=
 =?us-ascii?Q?V0S0S6Ct79KSbzMsCrTBgiotYllhnzHLpaXsvnW0lb8XN90jWUuezUocnBkI?=
 =?us-ascii?Q?4zspd83sIg=3D=3D?=
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-AuthSource: PH0PR11MB5880.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 2ba8e6af-37c6-4200-362d-08da34e2e682
X-MS-Exchange-CrossTenant-originalarrivaltime: 13 May 2022 13:17:16.0268
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: MTxSDz68jn4KlFhi3wFq3F1RIbVV+25pY5ewhQjS18NRGtEMGCQenxeNfTQpBdDurANfJaiOfyoUu3Jvp+z8tA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR11MB1247
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
	DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,RDNS_NONE,SPF_HELO_NONE,T_SCC_BODY_TEXT_LINE
	autolearn=unavailable autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


On Fri, May 13, 2022 at 08:42:55AM +0800, Zqiang wrote:
> If the CONFIG_RCU_STRICT_GRACE_PERIOD option is enabled, the normal=20
> grace period will be treated as expedited grace period, the gp_tasks=20
> that block current grace period needs to be boosted unconditionally,=20
> therefore this commit adds Kconfig check in rcu_initiate_boost().
>=20
> Signed-off-by: Zqiang <qiang1.zhang@intel.com>

>Good eyes!  I have queued this for further review and testing, thank you!
>
>What sorts of tests did you run on it?

Hi Paul

I didn't think of  suitable test method,
Can you provide me with a test method to test it, I will be happy to test.

Thanks,
Zqiang

>
>As usual, I could not resist the urge to wordsmith, so could you please ch=
eck the version shown below?
>
>							Thanx, Paul

------------------------------------------------------------------------

commit 079e0f894c5d887c678f94332c1fa7287abfd6bc
Author: Zqiang <qiang1.zhang@intel.com>
Date:   Fri May 13 08:42:55 2022 +0800

    rcu: Immediately boost preempted readers for strict grace periods
   =20
    The intent of the CONFIG_RCU_STRICT_GRACE_PERIOD Konfig option is to
    cause normal grace periods to complete quickly in order to better catch
    errors resulting from improperly leaking pointers from RCU read-side
    critical sections.  However, kernels built with this option enabled sti=
ll
    wait for some hundreds of milliseconds before boosting RCU readers that
    have been preempted within their current critical section.  The value
    of this delay is set by the CONFIG_RCU_BOOST_DELAY Kconfig option,
    which defaults to 500 milliseconds.
   =20
    This commit therefore causes kernels build with strict grace periods
    to ignore CONFIG_RCU_BOOST_DELAY.  This causes rcu_initiate_boost()
    to start boosting immediately after all CPUs on a given leaf rcu_node
    structure have passed through their quiescent states.
   =20
    Signed-off-by: Zqiang <qiang1.zhang@intel.com>
    Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 99cd=
e4c947699..b4ab952f04ea6 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1159,7 +1159,8 @@ static void rcu_initiate_boost(struct rcu_node *rnp, =
unsigned long flags)
 	    (rnp->gp_tasks !=3D NULL &&
 	     rnp->boost_tasks =3D=3D NULL &&
 	     rnp->qsmask =3D=3D 0 &&
-	     (!time_after(rnp->boost_time, jiffies) || rcu_state.cbovld))) {
+	     (!time_after(rnp->boost_time, jiffies) || rcu_state.cbovld ||
+	      IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)))) {
 		if (rnp->exp_tasks =3D=3D NULL)
 			WRITE_ONCE(rnp->boost_tasks, rnp->gp_tasks);
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);