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by tor.source.kernel.org (Postfix) with ESMTP id A010160007; Tue, 27 Jan 2026 11:30:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8DC14C16AAE; Tue, 27 Jan 2026 11:29:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769513402; bh=3MHBv5qz4r9u9+OGOCDEClZYEfFFg6c1ucfZG1KC7LY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=RlhbehXugRDNE89V27O40PiZgmYwl8Axy1aRlayHkNTbaRn5r/3c0+37Ma5pvSeZe O7sTRbMiVAo07NKBxmafRF7t34czQjKMW/sq9HxMBYOiNR4Zl9dOee3g+V8Po9fTYZ 2eEWEWiiO2wYWOCD/n4br4sozm5WAPlhI8RJLSKi5xKub3eJRYzzYG24jCmWiFcFUg IX53gmZo5JOszng/6q+mQgk6cziuIvl7M72wjS/cAlM3dob+Aq9bXSJHb4SvCJkg0K OIuTx+JPafcw9mUmlf668e0O1J0wyj+A1wI37rJX9dc3WwLqV1PBDLfji4UTmsHasY JFcuwUAZ5jnOQ== Message-ID: Date: Tue, 27 Jan 2026 12:29:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 7/7] mm: make PT_RECLAIM depends on MMU_GATHER_RCU_TABLE_FREE To: Qi Zheng , Andreas Larsson Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-alpha@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-um@lists.infradead.org, Qi Zheng , sparclinux , will@kernel.org, peterz@infradead.org, akpm@linux-foundation.org, aneesh.kumar@kernel.org, npiggin@gmail.com, dev.jain@arm.com, ioworker0@gmail.com, linmag7@gmail.com References: <9199f28e-e2b7-48c8-b61f-0b787e322443@gaisler.com> <646d9b5c-453c-4db8-b578-0f343e170379@linux.dev> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 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X-Stat-Signature: 8chbyxtdj6aeu8h8y5dpj8kr6o3bc3ni X-Rspam-User: X-HE-Tag: 1769513403-583507 X-HE-Meta: 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 COBJFskQ OcMP/u+WGBYjAAuoGqerY68Q5OOTxNCnHXyDIYJUyPupVN4n3fh6StP8ezwe0jlThkDOtinrvLZpNoMk6mYJtTjXcmuOUblK2DZdZCow4GmdohhSO73vm+w+oFv1QQ7Dc8QehtMHUz/LGoMDUKAEpvuWVrpgbREAQ2644GOzJ+0uXLyWYKK6ru08QWCX7Oo32vKO6CDQwVGfieiKdPVX1K8mp1VipUcYfm3C4CbDuljA0IKqtpv8LX6fbhGufPKOlKF0X0Z9K/GLGuDmnsRfnsYJxEMg6YCD2jtPn1mDnQRG5hx0EItUfQ75snZbrmdxqCvZfNKkmajqcB30= 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 1/26/26 07:59, Qi Zheng wrote: > > > On 1/23/26 11:15 PM, Andreas Larsson wrote: >> On 2025-12-17 10:45, Qi Zheng wrote: >>> From: Qi Zheng >>> >>> The PT_RECLAIM can work on all architectures that support >>> MMU_GATHER_RCU_TABLE_FREE, so make PT_RECLAIM depends on >>> MMU_GATHER_RCU_TABLE_FREE. >>> >>> BTW, change PT_RECLAIM to be enabled by default, since nobody should want >>> to turn it off. >>> >>> Signed-off-by: Qi Zheng >>> --- >>> arch/x86/Kconfig | 1 - >>> mm/Kconfig | 9 ++------- >>> 2 files changed, 2 insertions(+), 8 deletions(-) >>> >>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >>> index 80527299f859a..0d22da56a71b0 100644 >>> --- a/arch/x86/Kconfig >>> +++ b/arch/x86/Kconfig >>> @@ -331,7 +331,6 @@ config X86 >>> select FUNCTION_ALIGNMENT_4B >>> imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI >>> select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE >>> - select ARCH_SUPPORTS_PT_RECLAIM if X86_64 >>> select ARCH_SUPPORTS_SCHED_SMT if SMP >>> select SCHED_SMT if SMP >>> select ARCH_SUPPORTS_SCHED_CLUSTER if SMP >>> diff --git a/mm/Kconfig b/mm/Kconfig >>> index bd0ea5454af82..fc00b429b7129 100644 >>> --- a/mm/Kconfig >>> +++ b/mm/Kconfig >>> @@ -1447,14 +1447,9 @@ config ARCH_HAS_USER_SHADOW_STACK >>> The architecture has hardware support for userspace shadow call >>> stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss). >>> >>> -config ARCH_SUPPORTS_PT_RECLAIM >>> - def_bool n >>> - >>> config PT_RECLAIM >>> - bool "reclaim empty user page table pages" >>> - default y >>> - depends on ARCH_SUPPORTS_PT_RECLAIM && MMU && SMP >>> - select MMU_GATHER_RCU_TABLE_FREE >>> + def_bool y >>> + depends on MMU_GATHER_RCU_TABLE_FREE >>> help >>> Try to reclaim empty user page table pages in paths other than munmap >>> and exit_mmap path. >> >> Hi, >> >> This patch unfortunately results in a WARN_ON_ONCE and unaligned >> accesses on sparc64: >> >> $ stress-ng --mmaphuge 20 -t 60 >> stress-ng: info: [559] setting to a 1 min run per stressor >> stress-ng: info: [559] dispatching hogs: 20 mmaphuge >> [ 560.592569] ------------[ cut here ]------------ >> [ 560.592663] WARNING: kernel/rcu/tree.c:3098 at __call_rcu_common.constprop.0+0x200/0x760, CPU#4: stress-ng-mmaph/568 >> [ 560.592777] CPU: 4 UID: 1000 PID: 568 Comm: stress-ng-mmaph Not tainted 6.19.0-rc5-00127-g62fc9f6ccb97 #8 VOLUNTARY >> [ 560.592805] Call Trace: >> [ 560.592812] [<00000000004368b8>] dump_stack+0x8/0x60 >> [ 560.592844] [<0000000000482a60>] __warn+0xe0/0x140 >> [ 560.592878] [<0000000000482b64>] warn_slowpath_fmt+0xa4/0x120 >> [ 560.592901] [<0000000000526a40>] __call_rcu_common.constprop.0+0x200/0x760 >> [ 560.592931] [<0000000000526fd0>] call_rcu+0x10/0x20 >> [ 560.592954] [<0000000000730838>] tlb_remove_table+0x98/0xc0 >> [ 560.592986] [<000000000071bec4>] free_pgd_range+0x224/0x4c0 >> [ 560.593021] [<000000000071c35c>] free_pgtables+0x1fc/0x240 >> [ 560.593042] [<000000000074a6f0>] vms_clear_ptes+0x110/0x140 >> [ 560.593068] [<000000000074c3dc>] vms_complete_munmap_vmas+0x5c/0x280 >> [ 560.593094] [<000000000074de5c>] do_vmi_align_munmap+0x1dc/0x260 >> [ 560.593117] [<000000000074df80>] do_vmi_munmap+0xa0/0x140 >> [ 560.593142] [<000000000074fb2c>] __vm_munmap+0x8c/0x160 >> [ 560.593168] [<000000000072cfd4>] vm_munmap+0x14/0x40 >> [ 560.593190] [<00000000004402a8>] sys_64_munmap+0x88/0xa0 >> [ 560.593221] [<0000000000406274>] linux_sparc_syscall+0x34/0x44 >> [ 560.593274] ---[ end trace 0000000000000000 ]--- >> [ 560.593960] log_unaligned: 209 callbacks suppressed >> [ 560.593979] Kernel unaligned access at TPC[526a4c] __call_rcu_common.constprop.0+0x20c/0x760 >> [ 560.594121] Kernel unaligned access at TPC[526864] __call_rcu_common.constprop.0+0x24/0x760 >> [ 560.594198] Kernel unaligned access at TPC[52b3c4] rcu_segcblist_enqueue+0x24/0x40 >> [ 560.594275] Kernel unaligned access at TPC[526860] __call_rcu_common.constprop.0+0x20/0x760 >> [ 560.594360] Kernel unaligned access at TPC[526864] __call_rcu_common.constprop.0+0x24/0x760 >> [ 567.054127] log_unaligned: 1105 callbacks suppressed >> [ 567.054167] Kernel unaligned access at TPC[526860] __call_rcu_common.constprop.0+0x20/0x760 >> [ 567.054331] Kernel unaligned access at TPC[526864] __call_rcu_common.constprop.0+0x24/0x760 >> [ 567.054410] Kernel unaligned access at TPC[52b3c4] rcu_segcblist_enqueue+0x24/0x40 > > Thanks for your report! > > On sparc64, pmd and pud levels are not of struct page: Can you elaborate, I don't understand what you mean :) Is it also a problem on architectures like s390x and ppc, where we squeeze multiple page tables into a physical pages? > > __pmd_free_tlb/__pud_free_tlb > --> pgtable_free_tlb(tlb, pud/pmd, false). <=== is_page == false > --> tlb_remove_table > > So in __tlb_remove_table_one(), the table cannot be treated as > ptdesc because it does not have an pt_rcu_head member. > > Hi David, it seems we still need to keep ARCH_SUPPORTS_PT_RECLAIM? Or we invert it and only disable it for the known-problematic architectures? -- Cheers David