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[67.164.59.41]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7722a4bd1ccsm13897224b3a.47.2025.09.02.10.01.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Sep 2025 10:01:41 -0700 (PDT) Date: Tue, 2 Sep 2025 10:01:39 -0700 From: "Vishal Moola (Oracle)" To: Dan Carpenter Cc: oe-kbuild@lists.linux.dev, lkp@intel.com, oe-kbuild-all@lists.linux.dev, Andrew Morton , Linux Memory Management List Subject: Re: [linux-next:master 4756/5283] kernel/fork.c:457 account_kernel_stack() warn: we never enter this loop Message-ID: References: <202508300929.TrRovUMu-lkp@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202508300929.TrRovUMu-lkp@intel.com> X-Rspamd-Queue-Id: 47019140014 X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: ghfayaogmrpans645wieht33pd5mkamd X-HE-Tag: 1756832504-730542 X-HE-Meta: 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 oWQXP0O9 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 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: List-Subscribe: List-Unsubscribe: On Mon, Sep 01, 2025 at 01:56:05PM +0300, Dan Carpenter wrote: > tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master > head: 3cace99d63192a7250461b058279a42d91075d0c > commit: e0aa7237ef4323a66ed06953225d9b07cf039530 [4756/5283] mm: tag kernel stack pages > config: hexagon-randconfig-r072-20250829 (https://download.01.org/0day-ci/archive/20250830/202508300929.TrRovUMu-lkp@intel.com/config) > compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261) > > If you fix the issue in a separate patch/commit (i.e. not just a new version of > the same patch/commit), kindly add following tags > | Reported-by: kernel test robot > | Reported-by: Dan Carpenter > | Closes: https://lore.kernel.org/r/202508300929.TrRovUMu-lkp@intel.com/ > > smatch warnings: > kernel/fork.c:457 account_kernel_stack() warn: we never enter this loop > kernel/fork.c:457 account_kernel_stack() warn: unsigned 'i' is never less than zero. > kernel/fork.c:479 exit_task_stack_account() warn: we never enter this loop > kernel/fork.c:479 exit_task_stack_account() warn: unsigned 'i' is never less than zero. Thanks for catching this! > vim +457 kernel/fork.c > > ba14a194a434cc Andy Lutomirski 2016-08-11 437 static void account_kernel_stack(struct task_struct *tsk, int account) > c6a7f5728a1db4 KOSAKI Motohiro 2009-09-21 438 { > 0ce055f85335e4 Sebastian Andrzej Siewior 2022-02-17 439 if (IS_ENABLED(CONFIG_VMAP_STACK)) { > 449e0b4ed5a16c Pasha Tatashin 2025-05-09 440 struct vm_struct *vm_area = task_stack_vm_area(tsk); > 27faca83a7e955 Muchun Song 2021-04-29 441 int i; > efdc94907977d2 Andy Lutomirski 2016-07-28 442 > e0aa7237ef4323 Vishal Moola (Oracle 2025-08-20 443) for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { > 449e0b4ed5a16c Pasha Tatashin 2025-05-09 444 mod_lruvec_page_state(vm_area->pages[i], NR_KERNEL_STACK_KB, > 27faca83a7e955 Muchun Song 2021-04-29 445 account * (PAGE_SIZE / 1024)); > e0aa7237ef4323 Vishal Moola (Oracle 2025-08-20 446) __SetPageStack(vm_area->pages[i]); > e0aa7237ef4323 Vishal Moola (Oracle 2025-08-20 447) } > 27faca83a7e955 Muchun Song 2021-04-29 448 } else { > 0ce055f85335e4 Sebastian Andrzej Siewior 2022-02-17 449 void *stack = task_stack_page(tsk); > e0aa7237ef4323 Vishal Moola (Oracle 2025-08-20 450) struct page *page = virt_to_head_page(stack); > e0aa7237ef4323 Vishal Moola (Oracle 2025-08-20 451) int i; > 0ce055f85335e4 Sebastian Andrzej Siewior 2022-02-17 452 > 991e7673859ed4 Shakeel Butt 2020-08-06 453 /* All stack pages are in the same node. */ > da3ceeff923e3b Muchun Song 2020-12-14 454 mod_lruvec_kmem_state(stack, NR_KERNEL_STACK_KB, > efdc94907977d2 Andy Lutomirski 2016-07-28 455 account * (THREAD_SIZE / 1024)); > e0aa7237ef4323 Vishal Moola (Oracle 2025-08-20 456) > e0aa7237ef4323 Vishal Moola (Oracle 2025-08-20 @457) for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++, page++) > e0aa7237ef4323 Vishal Moola (Oracle 2025-08-20 458) __SetPageStack(page); > > Apparently in the linked config the THREAD_SIZE / PAGE_SIZE is zero. > Is this the expected behavior? I don't know mm enough to say the > answer... THREAD_SIZE and PAGE_SIZE are very architecture dependent. This behavior is expected in some configs. This can't happen in the VMAP_STACK case, only !VMAP_STACK, so looks like my patch is wrong in handling that case. I'll send a fix shortly.