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(p200300f6ef1b2000944ccbc71e1c2c47.dip0.t-ipconnect.de. [2003:f6:ef1b:2000:944c:cbc7:1e1c:2c47]) by smtp.gmail.com with ESMTPSA id ty24-20020a170907c71800b00a3ee41cbe87sm3762669ejc.153.2024.02.23.02.41.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Feb 2024 02:41:40 -0800 (PST) Message-ID: Subject: Re: [PATCH 1/2] driver core: Introduce device_link_wait_removal() From: Nuno =?ISO-8859-1?Q?S=E1?= To: Herve Codina , Saravana Kannan Cc: Greg Kroah-Hartman , "Rafael J. Wysocki" , Rob Herring , Frank Rowand , Lizhi Hou , Max Zhen , Sonal Santan , Stefano Stabellini , Jonathan Cameron , linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, Allan Nielsen , Horatiu Vultur , Steen Hegelund , Thomas Petazzoni , Android Kernel Team Date: Fri, 23 Feb 2024 11:45:02 +0100 In-Reply-To: <20240223101115.6bf7d570@bootlin.com> References: <20231130174126.688486-1-herve.codina@bootlin.com> <20231130174126.688486-2-herve.codina@bootlin.com> <20240223101115.6bf7d570@bootlin.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.4 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2024-02-23 at 10:11 +0100, Herve Codina wrote: > Hi Saravana, >=20 > On Tue, 20 Feb 2024 16:31:13 -0800 > Saravana Kannan wrote: >=20 > ... >=20 > > > +void device_link_wait_removal(void) > > > +{ > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * devlink removal jobs ar= e queued in the dedicated work queue. > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * To be sure that all rem= oval jobs are terminated, ensure that > > > any > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * scheduled work has run = to completion. > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */ > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 drain_workqueue(fw_devlink_wq);= =C2=A0=20 > >=20 > > Is there a reason this needs to be drain_workqueu() instead of > > flush_workqueue(). Drain is a stronger guarantee than we need in this > > case. All we are trying to make sure is that all the device link > > remove work queued so far have completed. >=20 > I used drain_workqueue() because drain_workqueue() allows for jobs alread= y > present in a workqueue to re-queue a job and drain_workqueue() will wait > also for this new job completion. >=20 > I think flush_workqueue() doesn't wait for this chain queueing. >=20 > In our case, my understanding was that device_link_release_fn() calls > put_device() for the consumer and the supplier. > If refcounts reaches zero, devlink_dev_release() can be called again > and re-queue a job. >=20 Looks sensible. The only doubt (that Saravana mays know better) is that I'm= not sure put_device() on a supplier or consumer can actually lead to devlink_dev_release(). AFAIU, a consumer or a supplier should not be a devi= ce from the devlink class. Hence, looking at device_release(), I'm not sure it= can happen unless for some odd reason someone is messing with devlinks in .remo= ve() or .type->remove(). - Nuno S=C3=A1