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Mon, 10 Aug 2026 15:55:05 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface MIME-Version: 1.0 X-ThreadId: ATK9jC40M2-k Date: Mon, 10 Aug 2026 21:54:45 +0200 From: "Arnd Bergmann" To: "David Summers" , arm Cc: "Andrew Lunn" , "Gregory Clement" , linux-arm-kernel@lists.infradead.org Message-Id: In-Reply-To: <5cb9b531-29c3-4928-aba6-5f14560e046f@davidjohnsummers.uk> References: <5cb9b531-29c3-4928-aba6-5f14560e046f@davidjohnsummers.uk> Subject: Re: Marvell Kirkwood and the linux 7.1.5 kernel Content-Type: text/plain Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260810_125520_206916_B7BD8470 X-CRM114-Status: GOOD ( 20.53 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Aug 10, 2026, at 17:59, David Summers wrote: > Hi All, > > I've an ancient nas I'm updating, that has Marvell Kirkwood core. I > recently updated to the 7.1.5 kernel, and now my kernel is hitting many > bugs, specifically: > >> [ 3.195064] BUG: using smp_processor_id() in preemptible [00000000] code: kworker/u4:1/49 >> [ 3.203374] caller is __flush_anon_page+0x28/0xd8 >> [ 3.208146] CPU: 0 UID: 0 PID: 49 Comm: kworker/u4:1 Not tainted 7.1.5-1-ARCH #3 PREEMPT >> [ 3.216370] Hardware name: Marvell Kirkwood (Flattened Device Tree) >> [ 3.222666] Call trace: >> [ 3.222677] unwind_backtrace from show_stack+0x10/0x14 >> [ 3.230489] show_stack from dump_stack_lvl+0x38/0x48 >> [ 3.235573] dump_stack_lvl from check_preemption_disabled+0x104/0x118 >> [ 3.242139] check_preemption_disabled from __flush_anon_page+0x28/0xd8 >> [ 3.248791] __flush_anon_page from __get_user_pages+0x420/0x608 >> [ 3.254844] __get_user_pages from get_user_pages_remote+0xd0/0x404 >> [ 3.261148] get_user_pages_remote from get_arg_page+0x6c/0xec >> [ 3.267025] get_arg_page from copy_string_kernel+0x98/0x194 >> [ 3.272720] copy_string_kernel from kernel_execve+0xa0/0x19c >> [ 3.278501] kernel_execve from call_usermodehelper_exec_async+0x120/0x238 >> [ 3.285425] call_usermodehelper_exec_async from ret_from_fork+0x14/0x28 >> [ 3.292164] Exception stack(0xe0b2dfb0 to 0xe0b2dff8) >> [ 3.297243] dfa0: 00000000 00000000 00000000 00000000 >> [ 3.305458] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 >> [ 3.313672] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000 >> > And this bug gets hit multiple times for each command run. > > I've tracked smp_processor_id() to linux/arch/arm/include/asm/smp.h > which contains: > > #define raw_smp_processor_id() (current_thread_info()->cpu) Since you confirmed that CONFIG_SMP is disabled, we can tell that this is not the location that caused the BUG() above, instead the warning does come from lib/smp_processor_id.c when CONFIG_DEBUG_PREEMPT is enabled, and this happens regardless of CONFIG_SMP. I think this most likely comes from this function: static inline void vivt_flush_cache_pages(struct vm_area_struct *vma, unsigned long user_addr, unsigned long pfn, unsigned int nr) { struct mm_struct *mm = vma->vm_mm; if (!mm || cpumask_test_cpu(smp_processor_id(), mm_cpumask(mm))) { unsigned long addr = user_addr & PAGE_MASK; __cpuc_flush_user_range(addr, addr + nr * PAGE_SIZE, vma->vm_flags); } } which only gets called on uniprocessor Armv4/Armv5 systems with an aliasing VIPT cache, and those are relatively rare. smp_processor_id() checks that it is called in an atomic section because the CPU might change under it on SMP kernels otherwise, but __get_user_pages() is definitely not an atomic context. I checked the same code path in linux-5.15 and I don't see any changes that would explain why you did not see the same issue earlier. Can you try to turn off CONFIG_DEBUG_PREEMPT? The specific warning here looks like a false positive since you can't get there on an SMP system, but it may be that there are other similar issues if you see a lot of different warnings. Arnd