Subject: Re: [PATCH] staging: vc04_services: Fix RCU dereference check
To:     Padmanabha Srinivasaiah <treasure4paddy@gmail.com>,
        linux-rpi-kernel@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org,
        linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org
Cc:     gregkh@linuxfoundation.org, nsaenz@kernel.org,
        Gaston Gonzalez <gascoar@gmail.com>,
        Ojaswin Mujoo <ojaswin98@gmail.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Phil Elwell <phil@raspberrypi.com>,
        bcm-kernel-feedback-list@broadcom.com
References: <20211229153243.6064-1-treasure4paddy@gmail.com>
From:   Stefan Wahren <stefan.wahren@i2se.com>
Autocrypt: addr=stefan.wahren@i2se.com; keydata=
 LS0tLS1CRUdJTiBQR1AgUFVCTElDIEtFWSBCTE9DSy0tLS0tClZlcnNpb246IEdudVBHIHYy
 CgptUUlOQkZ0NmdCTUJFQUN1Yi9wQmV2SHhidkplZnlaRzMySklObW4yYnNFUFgyNVY2ZmVq
 bXlZd21DR0tqRnRMCi9Eb1VNRVZIRHhDSjQ3Qk1YbzM0NGZIVjFDM0FudWRnTjFCZWhMb0J0
 TEh4bW5lQ3pnSDNLY1B0V1c3cHRqNEcKdEp2OUNRRFp5MjdTS29FUHh5YUk4Q0YweWdSeEpj
 NzJNOUk5d21zUFo1YlVIc0x1WVdNcVE3SmNSbVBzNkQ4ZwpCa2srOC95bmdFeU5FeHd4SnBS
 MXlsajVianhXREh5WVF2dUo1THpaS3VPOUxCM2xYVnNjNGJxWEVqYzZWRnVaCkZDQ2svc3lp
 by9ZaHNlOE4rUXN4N01RYWd6NHdLVWtRUWJmWGcxVnFrVG5BaXZYczQyVm5Ja211NWd6SXcv
 MHQKUkp2NTBGUmhIaHhweUtBSThCOG5oTjhRdng3TVZrUGM1dkRmZDN1R1lXNDdKUGhWUUJj
 VXdKd05rLzQ5RjllQQp2ZzJtdE1QRm5GT1JrV1VSdlArRzZGSmZtNitDdk92N1lmUDF1ZXdB
 aTRsbitKTzFnK2dqVklXbC9XSnB5MG5UCmlwZGZlSDlkSGtnU2lmUXVuWWN1Y2lzTXlvUmJG
 OTU1dENna0VZOUVNRWRZMXQ4aUdEaUNnWDZzNTBMSGJpM2sKNDUzdWFjcHhmUVhTYUF3UGtz
 bDhNa0NPc3YyZUVyNElOQ0hZUUR5WmljbEJ1dUNnOEVOYlI2QUdWdFpTUGNRYgplbnpTektS
 Wm9POUNhcUlEK2ZhdkxpQi9kaHptSEErOWJnSWhtWGZ2WFJMRFp6ZThwbzFkeXQzRTFzaFhp
 ZGRaClBBOE51SlZ6RUl0MmxtSTZWOHBaRHBuMjIxcmZLaml2UlFpYW9zNTRUZ1pqak1ZSTdu
 bko3ZTZ4endBUkFRQUIKdENCVGRHVm1ZVzRnVjJGb2NtVnVJRHgzWVdoeVpXNXpkRUJuYlhn
 dWJtVjBQb2tDTndRVEFRZ0FJUVVDWElkYwo0Z0liQXdVTENRZ0hBZ1lWQ0FrS0N3SUVGZ0lE
 QVFJZUFRSVhnQUFLQ1JDVWdld1BFWkR5MjFPVEQvOUdpWkxkCnRSWWNteVJKZ2x0aVFRekFp
 UWRjSUQ3OGxHb1dwL3grci92Y1U2YjZqdVl1ZVR3Z1Iwclc3djdsMklSQnlEN24KSEp4YSt0
 SVNvUVpCZ2hvbE1JZmI5TXRoR09KTENZNzdrL1FoQWhuMzJOR1prZWp3OXR6a3MvNDBtclpT
 VVQ4NApaeWJzUVhyTE0vSFI2VElJL0RlUEIwbktEM0ppcHBzMlVIUUQ5cUQySWpFd1NRUGxI
 akNPckVaaDQ1UFo3bTkrClo5M0x6aVRlc1dabFlRdUxpSndzNHJLcHRIVzFkL3dSZWxzaG1t
 NlFxY0wybDRDL2U0MGVEQjlncTRkU1poOVgKUEVZbGxpeU5RaDdhMkxTZHVtRTFyK2NTd0lq
 RS91ZHRSdmRPOWFLb0psT2JVSzVkTmpTUEg3d0tUYndkWGRZRApHUHdEaFhkNThOQXdyK1BY
 QmxQajB0STFMQ3ErTEJ4ZUt6aFdYK0dWcTlEb2pWanlVREV4Rk5Ga1h1b0M3ZzhtClY5VDB0
 ZUJpdVpSbm91WEt3VjJGcHRaT0hIN0JVRVd0a0t0aGgxZXRmT1dwaWdCemtVN2JQc2ZJWVQr
 cnk5dGIKMW9KK3Y0MVBOYXFaRW1QVXBKeHZmek5UN3Ayd01lRDdaajlmMHJ1YlJQdExBSjJR
 R2pyRkhzdVh3QU9xcHl6ZQoxOEVidHNZazBOMHp1SEVoY2orUEJJQmZoMFlJWWQ1MW9mNkdJ
 aU95UjlxMFhYdHBsVUo3VDIvSDF1UXFrWGxwCitnVzRWa2lmc2NJckl1eWZueFpXMTJlSXZq
 NnlicVdMN2FZS0dZbVQ2aUxDUGJIWXlZY2F5bDRFa0ZjckNGN0UKZTBXVC9zY1ZNaE8vNVgv
 SGFOQTVIQngvcjUycGdMY3Y0aTlNeExRbVUzUmxabUZ1SUZkaGFISmxiaUE4YzNSbApabUZ1
 TG5kaGFISmxia0JwTW5ObExtTnZiVDZKQWpnRUV3RUNBQ0lGQWx0NmdCTUNHd01HQ3drSUJ3
 TUNCaFVJCkFna0tDd1FXQWdNQkFoNEJBaGVBQUFvSkVKU0I3QThSa1BMYmpic1AvamdqYVNz
 NUh0bGtBSXZXUytGcm15N2MKaG5jT0F4TFRWL0Q2UkV3SU95R0poRkt3d29pck55UTJnOXZV
 YTNZQ1lDZjFmSjh3RWhhS09COWQwTHBNUm5MNApkRVQ4ZDgyMzhFL3BLK0hxTktpSXNKaHM2
 SnNLOFpnalZRR3JtbWZua0dyWisxdjBIQnV4ZGljZ0duUC9XdHVBClVsOGw2Mi9BTGJheXlq
 KzYxQ2xyc0V0UklhcU82N0xJWXdQaVBEUkkrWGlNek5pR3pIRi8xUTZHUjAyUkg2YTMKRjg5
 ejhhUHhjSGkxWnZDdDJ5a3o2VUVjaHpQMHI1Z3FGSisvTC9VcHU4ME1YaVk0djVlSWFCNTJn
 VlBnaXlNQQpsTDJkRHMxbUladm5yUkxSWTJ0YjNtQVlOa1Y1QjVJRFQzcGtXeTZrS281T0Nn
 SytZZFlPUjhGTloyb04ydDhPCnJLK1ZudGFLN01NU0tIbG1ZL3NPd3RSbEVoMU9CbXJjQ3dH
 d21wLzA1R2tSNDZmL0lzaFJWZUZPUmF3K0dBcXQKUDIrQ0ZhMkNOQS9JSG5aTm95aWtsRHpQ
 UUhVVUdzck5wcERyaFg5Sm1oQm1nMXYyeXdIMU5YdTFpRGZQMUJBdwpLZ29rdDVmNVVhUkY5
 c0FBNTN2V0V2YlVVTjllZXNGR0x6UFdkSkdRNWhwZC9WSDVJUXk5U0JyaC93SWNla3E1Cm4w
 a042cGJUSHhHRTUyU2kvTVZJa05UdURaM2FwbjJqbERaNHBPdHBCWEkydlAzYlBPK05pcUJa
 anNVM3R4TGkKV2R2MkZqeXp6NlhMUndlV1JZVkw1SGE2TER0eG9yMnZ1NlVQMDdwOXh6MXhS
 WmFPRFczb1lsSEZ6WXBhNFc1ZwpMSGIybEVrSXVVZlNjaWNHYmpqQXRDbFRkR1ZtWVc0Z1Yy
 Rm9jbVZ1SUR4emRHVm1ZVzR1ZDJGb2NtVnVRR2x1CkxYUmxZMmd1WTI5dFBva0NOd1FUQVFn
 QUlRVUNYSWRlaHdJYkF3VUxDUWdIQWdZVkNBa0tDd0lFRmdJREFRSWUKQVFJWGdBQUtDUkNV
 Z2V3UEVaRHkyeUhURC85VUY3UWxEa0d4elE3QWFDSTZOOTVpUWY4LzFvU1VhRE51Mlk2SQpL
 K0R6UXBiMVRiVE9yM1ZKd3dZOGEzT1d6NU5MU09MTVdlVnh0K29zTW1sUUlHdWJEM09EWko4
 aXpQbEcvSnJOCnQ1elNkbU41SUE1ZjNlc1dXUVZLdmdoWkFnVERxZHB2K1pIVzJFbXhuQUox
 dUxGWFhlUWQzVVpjQzVyMy9nL3YKU2FNbzl4ZWszSjVtTnVEbTcxbEVXc0FzL0JBY0ZjK3lu
 TGh4d0JXQld3c3Z3UjhiSHRKNURPTVd2YUt1RHNrcApJR0ZVZS9LYjJCK2pyYXZRM1RuNnMv
 SHFKTTBjZXhTSHo1cGUrMHNHdlArdDlKNzIzNEJGUXdlRkV4cmlleThVCkl4T3I0WEFiYWFi
 U3J5WW5VL3pWSDlVMWkyQUlRWk1XSkFldkN2VmdRL1UrTmVSaFh1ZGU5WVVtRE1EbzJzQjIK
 VkFGRUFxaUYyUVVIUEEybThhN0VPM3lmTDRyTWswaUh6TElLdmg2L3JIOFFDWThpM1h4VE5M
 OWlDTHpCV3UvTgpPbkNBYlMremx2TFphaVNNaDVFZnV4VHR2NFBsVmRFamY2MlArWkhJRDE2
 Z1VEd0VtYXpMQU1yeDY2NmpINWt1ClVDVFZ5bWJMMFR2Qis2TDZBUmw4QU55TTRBRG1rV2tw
 eU0yMmtDdUlTWUFFZlFSM3VXWFo5WWd4YVBNcWJWK3cKQnJoSmc0SGFONkM2eFRxR3YzcjRC
 MmFxYjc3L0NWb1JKMVo5Y3BIQ3dpT3pJYUFtdnl6UFU2TXhDRFhaOEZnWQpsVDR2MjNHNWlt
 SlAyemdYNXMrRjZBQ1VKOVVRUEQwdVRmK0o5RGEycitza2gvc1dPbloreWNvSE5CUXZvY1pF
 Ck5BSFFmN2tDRFFSYmVvQVRBUkFBMkhkMGZzRFZLNzJSTFNESGJ5ME9oZ0RjRGxWQk0yTSto
 WVlwTzNmWDFyKysKc2hpcVBLQ0hWQXNRNWJ4ZTdIbUppbUhhNEtLWXMya3YvbWx0L0NhdUNK
 Ly9wbWN5Y0JNN0d2d25Lem11WHp1QQpHbVZUWkM2V1I1TGtha0ZydEhPelZtc0VHcE52NVJj
 OWw2SFlGcExrYlNrVmk1U1BRWkp5K0VNZ01DRmdqclpmClZGNnlvdHdFMWFmN0hOdE1oTlBh
 TEROMW9VS0Y1aitSeVJnNWl3SnVDRGtuSGp3QlFWNHBndzIvNXZTOEE3WlEKdjJNYlcvVExF
 eXBLWGlmNzhJaGdBelh0RTJYck0xbi9vNlpINzFvUkZGS096NDJsRmR6ZHJTWDBZc3FYZ0hD
 WAo1Z0l0TGZxemoxcHNNYTlvMWVpTlRFbTFkVlFyVHFueXMwbDE4b2FsUk5zd1lsUW1uWUJ3
 cHdDa2FUSExNSHdLCmZHQmJvNWRMUEVzaHRWb3dJNm5zZ3FMVHlRSG1xSFlxVVpZSXBpZ21t
 QzNTd0JXWTFWNmZmVUVta3FwQUFDRW4KTDQvZ1Vnbjd5US81ZDBzZXFuQXEycFNCSE1VVW9D
 Y1R6RVFVV1ZraUR2M1JrN2hURm1oVHNNcTc4eHYyWFJzWApNUjZ5UWhTVFBGWkNZRFVFeEVs
 RXNTbzlGV0hXcjZ6SHlZY2M4cURMRnZHOUZQaG1RdVQyczlCbHg2Z0kzMjNHCm5FcTFsd1dQ
 SlZ6UDRqUWtKS0lBWHdGcHYrVzhDV0xxekRXT3ZkbHJEYVRhVk1zY0ZUZUg1VzZVcHJsNjVq
 cUYKUUdNcGNSR0NzOEdDVVcxM0gwSXlPdFF0d1dYQTRueStTTDgxcHZpQW1hU1hVOGxhS2FS
 dTkxVk9WYUY5ZjRzQQpFUUVBQVlrQ0h3UVlBUUlBQ1FVQ1czcUFFd0liREFBS0NSQ1VnZXdQ
 RVpEeTIrb1hELzljSEhSa0JaT2ZrbVNxCjE0U3Z4MDYyUHRVMEtWNDcwVFNucC9qV29ZSm5L
 SXczRzBtWElSZ3J0SDJkUHdwSWdWanNZeVJTVk1LbVNwdDUKWnJEZjlOdFRiTldnazhWb0xl
 WnpZRW8rSjNvUHFGclRNczNhWVl2N2U0K0pLNjk1WW5tUSttT0Q5bmlhOTE1dApyNUFaajk1
 VWZTVGx5VW15aWMxZDhvdnNmMWZQN1hDVVZSRmNSamZOZkRGMW9ML3BEZ01QNUdaMk93YVRl
 am15CkN1SGpNOElSMUNpYXZCcFlEbUJuVFlrN1B0aHk2YXRXdllsMGZ5L0NxYWpUS3N4Nytw
 OXh6aXU4WmZWWCtpS0IKQ2MrSGUrRURFZEdJRGh2TlovSVFIZk9CMlBVWFdHUytzOUZOVHhy
 L0E2bkxHWG5BOVk2dzkzaVBkWUl3eFM3SwpYTG9LSmVlMTBEamx6c1lzUmZsRk9XMFpPaVNp
 aElDWGlRVjF1cU02dHpGRzlndFJjaXVzNVVBdGhXYU8xT3dVClNDUW1mQ09tNGZ2TUlKSUE5
 cnh0b1M2T3FSUWNpRjNjcm1vMHJKQ3ROMmF3WmZnaThYRWlmN2Q2aGp2MEVLTTkKWFpvaUFa
 WVpEKy9pTG01VGFLV042b0dJdGkwVmpKdjhaWk9aT2ZDYjZ2cUZJa0pXK2FPdTRvclRMRk16
 MjhhbwpVM1F5V3BOQzhGRm1kWXNWdWE4czZnTjFOSWE2eTNxYS9aQjhiQS9pa3k1OUFFejRp
 RElScmdVek1FZzhBazdUCmZtMUtpWWVpVHRCRENvMjVCdlhqYnFzeXhrUUQxbmtSbTZGQVZ6
 RXVPUEllOEp1cVcyeEQ5aXhHWXZqVTVoa1IKZ0pwM2dQNWIrY25HM0xQcXF1UTJFNmdvS1VN
 TEFia0NEUVJiZmw5REFSQUFzRExjYStMbFAydm5mdEVHaHBjQQpCR1ZOUUVGbkdQckNhdVU2
 SGhOODA1V3RQVHRtc1JPdUp6cWdVVDBtcHFXSWZacTZzTXd5dkhLOVRzL0tIM0paClVWYlJD
 M3oyaDNLZmhIL0RhZjk1cGQ2bVBjL2g5dkYvT3kzK2VUV2hnR25QNmNBNWtsUitmTzFXaEc4
 VnJpWHYKck5lUkcyMHN6emplSG9jblNJY1Q1WHVaUjB1REhPaUd4T2l6MXNNUkZUR3h6R095
 MTlSOXJ2dTYzdGlJM2Q3dgpnYzc1T0NBZGtlQi9TZUNFbGFSdzBUZjdMWmJQampzRjI2M0JZ
 bk1mNGtrTkVLdnFXY1UyaWNNcCtxZXpqeW5CCnB2ZXVlMHJDVFFCWUFRbG9GQ1ZUR0hyV1dB
 NkQ0VzVPMkFmSWRJYzF1MUpDWnAyZjVMV1ZvVUZUVklyUW5RUVUKU0hDaWZyOU1aeExUdFBK
 ZFU1Mm9TUHczZGs0aExQOGlKSUx1dnYvYXZhakNzUVlIRXR3WXNiZUZaeGl1TGdscApBN1lj
 Sk5ObXBnQ3BNRDR3VWh2bEN0QUtOQlFXeXIyOTc2OThFUVRuNDZlQmVVNkttMkNpaFhrZ3dD
 eWY4ZXlLCkxFM3NYZXdhcTVrZ1pXdk5xNml1NXFZSVJCOXl3K2NYYzYwZE9aRE9scTkzWDVT
 QVJZemFvZXBrSHo0cmtMa1AKUG8rdENIeUhRUHNHblBYYzlXVDgwREM5Tm5KR2R2VWx5NXJk
 TUk0eHBaeWdlb2tqd293VlFsUFV1Y1M2TXluNwpmOHc4Y2dmQjdDMklBSWNEeDJwUC9IendY
 dmtDT1FOQTdtVjFsTTA4bitnVmtUcnpweGlwNURicTRDSW9ZeDJNCkpaVDhiR1JINlhqY1VE
 S2EwOVFoeVpzQUVRRUFBWWtFUkFRWUFRZ0FEd1VDVzM1ZlF3SWJBZ1VKQThKbkFBSXAKQ1JD
 VWdld1BFWkR5MjhGZElBUVpBUWdBQmdVQ1czNWZRd0FLQ1JCVnhETFBjVk1NamNkc0QvMFJo
 QXN1UVlPeQpyMTNCbDNOaFhrWUFaR3AyWkZER3VrZTdPU2tWOG9qT09UZFR5ei9jT1JHQ2J5
 ZEQrRGd2cUZ5VmRuT1hLZ08wCmxKbUd3ckdlTGRnZ0F2aDBpaHJwNU8wWVVKOWJCU1htR01t
 UVRZSC9BbUxUR2FkYnVqQ1dqNWZGVWtDeXd4aW0KSHV5MFBiMjRwelR2UzUwR1k1WStxSDBG
 SE5haWdka2tpV04zcnVnN0haRXUvQ3lsUFpqT1h6K0QxUVBNckV4dwo3ZC9NS2FiVis5YU5i
 UVlabGRJajk4UXd2VUYxS1N6YThqbFVJdnBoUnEyN0FUOGZER1lHUGZERU1nMmNCT2FlCkty
 N29uUXM0YjdhV082aWZEbHhRVHB6c3pvK0FuODA3Tk1TdFZFRmYrczNBaFZEM2U3bmY4SkJh
 dmJWckFlMGsKb20yNm96elBubnh6K2xxVlZ0dzZVazRYTUl6dGl4L0h3SFl3dUNuY1VYWndL
 MEkzeUFKd2pZd29vck9DaEozUwpFVWJKUVB0R3NneFJERXhWQkZlNk5MUC82MnhQOU82dGFj
 d09kYjBNbVAxYjM5cFJBVEM3YmdkMWxkVUxpNzVaCmxKckowL1NpVkVyb3FOWXk3OXRmbWdB
 WjJVeFptczlTckV5Nm85UVNmc24xYVh2K01QTDlKYUNHbWtQNnpiTFEKTm5kajBKY2FRbmtD
 MHZneWRPMUJtNk11OTZQOXVmbEtaY0FTNndtTE01SWRIT3lqTDg4d0h3anVjakFPQnRjdwpw
 MG9HVG5WT25Sc05ZU084VzhZWi9LZGJ1Nzg1ZGF6TXFKMmlOakFEdUJiZG02TjRqNUVkTW5r
 TG4wQklmUEpwCmRnbTR2bDJVcExqd1JHci9NM3dtbTVwdnMrNnVCN2hrL0ZKaUQvNGxsRU5Q
 NGVNMWg3U200aitWcTZOMSt6VEIKSVhKQWViSXFhc0RwNXlaUzdYcnk0STM2bjg1WEVZZkcw
 MWx0QXlob05WMkRPOFNJUlFwdWkydHErOVJQM1JLMQpKREJ4eEVKWTJFTzVKWjhNeGFQSFEw
 RFQwNWxSRmpLMkFsaGRFSXRqTGpwSjNmVW05c3FMeE1XeHpQNlV6M2lpCjJ1YTR1bnJ0Nk9D
 VHFRd2lqRi8zYlRXaXd2VkFBSG5NRlVpb1hzaEhhb2hWRGNWZm5lSU1mVjBiUUNYWWkzTnAK
 WTB2MFp3Y2lGSCtnU0M3cUQ2WE51aHBWR1NMNElpbGlGeS9TemNhSkV6QUhlTERTaFpQMkNX
 ZG5DNHZnbDM3dApocHg4aDU1WWhKbjZIU3VVelBnaGFLdFZCMmsrajdaZXlaK1NGeHA3SXVi
 SEN3TEhsUWhUNzVSd1EzaUF4S242CjBxajUxY1lUbnF4ZFpYVzZmSDNQa3VNellVNUdwcVIv
 MU9sNWMvd2ZJNmc2QW04eUtXLzBFVUx0K0tuNExGc1MKbTdZM201SDV2MTJVNkpCWXZWK3Ix
 M2paaW9zNEVFREU5M0Q1c05IMk1JeVJ6Q0RxMXpkZHQ0WHV5S0ZqUEtXMQo5aWJaRGZGVjdL
 dUNzdnVMMjNzQmMxc0NNb3ArRTFtVC9ReE9JQTZvRFQxTVFzdHdPVnVReURDdi9PdktTZ2Z6
 CjhGWEdMNkFQY2xqQ3FqOEFKaHhReXN4ZG9pUVA4bS92dStialdHR3Z4dzVzMWxncGlSRFRS
 VVBnY0pKTmFHWTIKVklEclpRaTROU2lOUTBOSWkrZGp1NGZOTW1DcFFxZzh0YkMzY0FhNnl3
 bTZvUUIxU0JobURYMmUxMWdSbGx1SQpPblRHUEUwSFRvM2w3MmxoYmc9PQo9cVpNVgotLS0t
 LUVORCBQR1AgUFVCTElDIEtFWSBCTE9DSy0tLS0tCg==
Message-ID: <a30849fa-dd7c-f661-0b27-a04c6531cfb8@i2se.com>
Date:   Wed, 29 Dec 2021 20:13:40 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <20211229153243.6064-1-treasure4paddy@gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Content-Language: en-US
Precedence: bulk

Hi Padmanabha,

Am 29.12.21 um 16:32 schrieb Padmanabha Srinivasaiah:
> In service_callback path RCU dereference done without
> rcu_read_[lock/unlock] pair, fixing same by using them.
>
> [   32.201659] =============================
> [   32.201664] WARNING: suspicious RCU usage
> [   32.201670] 5.15.11-rt24-v8+ #3 Not tainted
> [   32.201680] -----------------------------
> [   32.201685] drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h:529 suspicious rcu_dereference_check() usage!
> [   32.201695]
> [   32.201695] other info that might help us debug this:
> [   32.201695]
> [   32.201700]
> [   32.201700] rcu_scheduler_active = 2, debug_locks = 1
> [   32.201708] no locks held by vchiq-slot/0/98.
> [   32.201715]
> [   32.201715] stack backtrace:
> [   32.201723] CPU: 1 PID: 98 Comm: vchiq-slot/0 Not tainted 5.15.11-rt24-v8+ #3
> [   32.201733] Hardware name: Raspberry Pi 4 Model B Rev 1.4 (DT)
> [   32.201739] Call trace:
> [   32.201742]  dump_backtrace+0x0/0x1b8
> [   32.201772]  show_stack+0x20/0x30
> [   32.201784]  dump_stack_lvl+0x8c/0xb8
> [   32.201799]  dump_stack+0x18/0x34
> [   32.201808]  lockdep_rcu_suspicious+0xe4/0xf8
> [   32.201817]  service_callback+0x124/0x400
> [   32.201830]  slot_handler_func+0xf60/0x1e20
> [   32.201839]  kthread+0x19c/0x1a8
> [   32.201849]  ret_from_fork+0x10/0x20
>
> Signed-off-by: Padmanabha Srinivasaiah <treasure4paddy@gmail.com>
> ---
>  drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> index 6759a6261500..ee1b48db9681 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> @@ -1058,7 +1058,10 @@ service_callback(enum vchiq_reason reason, struct vchiq_header *header,
>  
>  	DEBUG_TRACE(SERVICE_CALLBACK_LINE);
>  
> +	rcu_read_lock();
>  	service = handle_to_service(handle);
> +	rcu_read_unlock();
> +
>  	if (WARN_ON(!service))
>  		return VCHIQ_SUCCESS;
>  

thanks for reporting this issue.

Could you please explain how to reproduce this issue?

What makes you sure that your patch fixes the issue and not just hiding
the warning?

Best regards