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Sat, 3 Mar 2018 19:30:23 -0500 Received: from mail-by2nam01on0124.outbound.protection.outlook.com ([104.47.34.124]:45281 "EHLO NAM01-BY2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932401AbeCCW2D (ORCPT ); Sat, 3 Mar 2018 17:28:03 -0500 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Arnd Bergmann , Jason Gunthorpe , Sasha Levin Subject: [PATCH AUTOSEL for 4.15 101/102] IB/mlx5: revisit -Wmaybe-uninitialized warning Thread-Topic: [PATCH AUTOSEL for 4.15 101/102] IB/mlx5: revisit -Wmaybe-uninitialized warning Thread-Index: AQHTsz58yx7HL5fbRk6C7X4SqVSK6g== Date: Sat, 3 Mar 2018 22:25:08 +0000 Message-ID: <20180303222318.26006-101-alexander.levin@microsoft.com> References: <20180303222318.26006-1-alexander.levin@microsoft.com> In-Reply-To: <20180303222318.26006-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;MW2SPR01MB06;7:FwMXJLQMhoV9lOzNrWolqCJLsLhmfV/NQ3wdsxSbSYIxah2n09NjGSFoh0IDBqn/VdBNDnOhaGrDwi0qVnpvaQvPi/yQfS9FowSZgaWwpb8jD6C/kAGtb3AAJkmdc9v4+qr4/shEnbAvBUK7LvFz6h/HGD0eWa8hPXlDquowg7X+DpH6OQ641n2lQ5BXL5UkBerxt31oGbPLlGQYW29cSmmMueI/Zt7agarCLTuH2DFKcJfPdcB1fdbs9yXIvY40 x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: d1282c2a-d638-403c-458e-08d58156027c x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(4627221)(201703031133081)(201702281549075)(48565401081)(5600026)(4604075)(3008032)(2017052603307)(7193020);SRVR:MW2SPR01MB06; 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x-microsoft-antispam-message-info: BeobVXZZqtkI8nZQzvtOz90ejzyoDHy8rBU14Q8snX1bIg6rnGEP5NFTke0L0vFvcOPGpZcnUuVH3BQsdVJYe/v+FTZyGOlaDvXgK+dfVI1GKm2k/qLMUd6ibTnK+GN6VTFqVUCmoxZctVFyt51zU8WWt2AM7eEErAhT9CVrIhU= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: d1282c2a-d638-403c-458e-08d58156027c X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Mar 2018 22:25:08.1659 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2SPR01MB06 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: Arnd Bergmann [ Upstream commit 1b19b95169cd52fe82cd442fec0b279fe25cc838 ] A warning that I thought I had fixed before occasionally comes back in rare randconfig builds (I found 7 instances in the last 100000 builds, originally it was much more frequent): drivers/infiniband/hw/mlx5/mr.c: In function 'mlx5_ib_reg_user_mr': drivers/infiniband/hw/mlx5/mr.c:1229:5: error: 'order' may be used uninitia= lized in this function [-Werror=3Dmaybe-uninitialized] if (order <=3D mr_cache_max_order(dev)) { ^ drivers/infiniband/hw/mlx5/mr.c:1247:8: error: 'ncont' may be used uninitia= lized in this function [-Werror=3Dmaybe-uninitialized] drivers/infiniband/hw/mlx5/mr.c:1247:8: error: 'page_shift' may be used uni= nitialized in this function [-Werror=3Dmaybe-uninitialized] drivers/infiniband/hw/mlx5/mr.c:1260:2: error: 'npages' may be used uniniti= alized in this function [-Werror=3Dmaybe-uninitialized] I've looked at all those findings again and noticed that they are all with CONFIG_INFINIBAND_USER_MEM=3Dn, which means ib_umem_get() returns an error unconditionally and we never initialize or use those variables. This triggers a condition in gcc iff mr_umem_get() is partially but not entirely inlined, which in turn depends on the exact combination of optimization settings. This is a known problem with gcc, with no easy solution in the compiler, so this adds another workaround that should be more reliable than my previous attempt. Returning an error from mlx5_ib_reg_user_mr() earlier means that we can completely bypass the logic that caused the warning, the compiler can now see that the variable is never accessed. Fixes: 14ab8896f5d9 ("IB/mlx5: avoid bogus -Wmaybe-uninitialized warning") Signed-off-by: Arnd Bergmann Signed-off-by: Jason Gunthorpe Signed-off-by: Sasha Levin --- drivers/infiniband/hw/mlx5/mr.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/m= r.c index d109fe8290a7..556e015678de 100644 --- a/drivers/infiniband/hw/mlx5/mr.c +++ b/drivers/infiniband/hw/mlx5/mr.c @@ -1206,6 +1206,9 @@ struct ib_mr *mlx5_ib_reg_user_mr(struct ib_pd *pd, u= 64 start, u64 length, int err; bool use_umr =3D true; =20 + if (!IS_ENABLED(CONFIG_INFINIBAND_USER_MEM)) + return ERR_PTR(-EINVAL); + mlx5_ib_dbg(dev, "start 0x%llx, virt_addr 0x%llx, length 0x%llx, access_f= lags 0x%x\n", start, virt_addr, length, access_flags); =20 --=20 2.14.1