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[77.53.209.86]) by smtp.gmail.com with ESMTPSA id r5sm3176931ljh.128.2021.03.10.05.54.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 10 Mar 2021 05:54:31 -0800 (PST) From: Jan Kardell Subject: arm: lockdep complaining about locks allocations in static memory To: Linux ARM Cc: linux-kernel@vger.kernel.org, Russell King , linux-omap@vger.kernel.org, Tony Lindgren , Andrew Morton , linux-mm@kvack.org Message-ID: <6df24716-8b41-8e9a-f2f4-a0f5d49643bd@telliq.com> Date: Wed, 10 Mar 2021 14:54:30 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0 SeaMonkey/2.53.5.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 4A230132 X-Stat-Signature: z1ejr99xrg8pgcbxdfrfqqhqwxb1mwgo Received-SPF: none (arkub.com>: No applicable sender policy available) receiver=imf29; identity=mailfrom; envelope-from=""; helo=mail-lj1-f181.google.com; client-ip=209.85.208.181 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615384470-557168 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi, During work lift the software and kernel versions on our custom TI am3352 board I started to see lockdep warnings after enabling CONFIG_PREEMT. Lockdep seems to think the memory that previously was initmem is static memory. I'm using linux 5.4, as that is what is used in the next OpenWrt version. [ 92.198989] WARNING: CPU: 0 PID: 2015 at kernel/locking/lockdep.c:1119 alloc_netdev_mqs+0xb4/0x3b0 I guess CONFIG_PREEMT just changes the timing of allocations, and is otherwise irrelevant. This was fixed for s390 in linux 5.2 commit 7a5da02de8d6eafba99556f8c98e5313edebb449 by adding the function arch_is_kernel_initmem_freed(). Later a very similar change was made for powerpc, and a different solution for x86. I now believe that is needed for arm as well. Though I don't know the inner workings of arm memory management so I don't know if an identical solution to s390 will do for arm, but my experiments suggests it works for am335x. The commit message for s390 says "virt == phys", but that seems not to be the case for my arm system. //Jan