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Wed, 21 Apr 2021 15:27:24 +0000 From: Michael Kelley To: Joe Perches , KY Srinivasan , Haiyang Zhang , Stephen Hemminger , "wei.liu@kernel.org" , "linux-kernel@vger.kernel.org" , "linux-hyperv@vger.kernel.org" , "linux-fbdev@vger.kernel.org" , "dri-devel@lists.freedesktop.org" Subject: RE: [PATCH 1/1] video: hyperv_fb: Add ratelimit on error message Thread-Topic: [PATCH 1/1] video: hyperv_fb: Add ratelimit on error message Thread-Index: AQHXNfwbMInj8J9Lc0erCaPnZXj03qq90y8AgAFDusA= Date: Wed, 21 Apr 2021 15:27:24 +0000 Message-ID: References: <1618933459-10585-1-git-send-email-mikelley@microsoft.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ActionId=d473cfa3-8c7f-4f20-8b7e-2d7e5f767aa5;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ContentBits=0;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=true;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Method=Standard;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Name=Internal;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SetDate=2021-04-21T15:17:27Z;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SiteId=72f988bf-86f1-41af-91ab-2d7cd011db47; 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charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: MWHPR21MB1593.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: aee71c07-f7e0-46aa-30bb-08d904d9f6ec X-MS-Exchange-CrossTenant-originalarrivaltime: 21 Apr 2021 15:27:24.5524 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: QoKHJ+bMR9g/svZovhOlf2vB8QmXgdafgyyHBFiJPkCeJ6DTxe1MdcXpS6BDp7BHgpBzKQxXRaahbfbYVvmTlbhXdT43deW/5W8fQscuvmc= X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR2101MB0905 Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org From: Joe Perches Sent: Tuesday, April 20, 2021 12:59 PM >=20 > On Tue, 2021-04-20 at 08:44 -0700, Michael Kelley wrote: > > Due to a full ring buffer, the driver may be unable to send updates to > > the Hyper-V host. But outputing the error message can make the problem > > worse because console output is also typically written to the frame > > buffer. As a result, in some circumstances the error message is output > > continuously. > > > > Break the cycle by rate limiting the error message. Also output > > the error code for additional diagnosability. > > > > Signed-off-by: Michael Kelley >=20 > None of the callers of this function ever check the return status. > Why is important/useful to emit this message at all? > Except during device initialization, the messages tell Hyper-V about updates to the frame buffer contents. The fbdev framework functions (such as fillrect) that eventually call synthvid_send() are void functions. So the message is the only alert that something has gone wrong in the communication with Hyper-V, which makes it useful for diagnostic purposes. Michael =20 > > --- > > =A0drivers/video/fbdev/hyperv_fb.c | 2 +- > > =A01 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hype= rv_fb.c > > index 4dc9077..a7e6eea 100644 > > --- a/drivers/video/fbdev/hyperv_fb.c > > +++ b/drivers/video/fbdev/hyperv_fb.c > > @@ -308,7 +308,7 @@ static inline int synthvid_send(struct hv_device *h= dev, > > =A0 VM_PKT_DATA_INBAND, 0); > > > > > > =A0 if (ret) > > - pr_err("Unable to send packet via vmbus\n"); > > + pr_err_ratelimited("Unable to send packet via vmbus; error %d\n", re= t); > > > > > > =A0 return ret; > > =A0} >=20