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Thu, 29 Jul 2021 04:59:37 +0000 From: Yoshihiro Shimoda To: "sergei.shtylyov@gmail.com" , "davem@davemloft.net" , "kuba@kernel.org" CC: "netdev@vger.kernel.org" , "linux-renesas-soc@vger.kernel.org" Subject: RE: [PATCH 0/2] ravb and sh_eth: Fix descriptor counters' conditions Thread-Topic: [PATCH 0/2] ravb and sh_eth: Fix descriptor counters' conditions Thread-Index: AQHXgsB5q+zR5LvdjkC8e4BVJ5YfVKtZZEWA Date: Thu, 29 Jul 2021 04:59:37 +0000 Message-ID: References: <20210727082147.270734-1-yoshihiro.shimoda.uh@renesas.com> In-Reply-To: <20210727082147.270734-1-yoshihiro.shimoda.uh@renesas.com> Accept-Language: ja-JP, en-US Content-Language: ja-JP X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: gmail.com; dkim=none (message not signed) header.d=none;gmail.com; dmarc=none action=none header.from=renesas.com; x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 60404a59-b117-4e56-a7f9-08d9524daab4 x-ms-traffictypediagnostic: TYYPR01MB6778: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:8882; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: renesas.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: TY2PR01MB3692.jpnprd01.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 60404a59-b117-4e56-a7f9-08d9524daab4 X-MS-Exchange-CrossTenant-originalarrivaltime: 29 Jul 2021 04:59:37.7902 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 53d82571-da19-47e4-9cb4-625a166a4a2a X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: vBDwa8F93gkb5T6yySm74FWQVpisyO/RT1fVPQZLE44dQzu3vLnHZmtxDhCc/PNv/AT8XjERxwc+LyOWEYlF05cilLWeU+9XlVeqG84S6dNeKYWi8aLZBGscOolx8Svd X-MS-Exchange-Transport-CrossTenantHeadersStamped: TYYPR01MB6778 Precedence: bulk List-ID: X-Mailing-List: linux-renesas-soc@vger.kernel.org Hi all, > From: Yoshihiro Shimoda, Sent: Tuesday, July 27, 2021 5:22 PM >=20 > When we change the type of {cur,dirty}_tx from u32 to u8, we can > reproduce this issue easily. I'm afraid but I would like to recall this patch series because the original code didn't have any issue around these counters so that the patch series should not be applied. For just a record, I tried to write why I misunderstood these counters are = incorrect below: - I got a report locally about an issue happen when the system sends/receiv= es data in long time transfer - So, I doubted these counters' overflow. - To reproduce the issue quickly, I changed the type from u32 to u8. - And then, the following condition will not work correctly (as I mentioned= on the patch). for (; priv->cur_tx[q] - priv->dirty_tx[q] > 0; priv->dirty_tx[q]++)= { --- [1] - Also, I found if we used "> 0U" instead of "0", the issue disappeared. for (; priv->cur_tx[q] - priv->dirty_tx[q] > 0U; priv->dirty_tx[q]++= ) { --- [2] ~~ - However, today I got a report from our team member locally. The object co= de of the get_num_desc() is just "from - subtract". - If we use u32 as the original code, I realized the object codes between [= 1] and [2] are the same. - Also, I realized just priv->cur_tx[q] - priv->dirty_tx[q] is no problem. - So, I would like to recall this patch series. Best regards, Yoshihiro Shimoda