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Fri, 23 Jan 2026 16:15:55 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gaisler.com; s=simplycom2; t=1769181355; bh=bZOD1qxujIU3XqsrT9Q0is3A3LXGMfjZia6aaXxikQM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ag1WRAWJtsN0/+CXBOsevJVeLpSL3/UnOj7eGnW5g7r2ql6jKEN6uMQEFz39jpWTj 70hB6mp8Ve1s6Wp5eFrGmiH/PwtssmQd+OO1x2dJ25+zQ8YZn2M7a8oa0nbx1j6rlf 1jVZ+eG2KhetS8xTd2rubzhycPTOvv5H3QVv5BOpKDJUbmQFZnHbjmifqmRJK+rcmN m8LMVMH5b3JJXy0dqOhyCLj8N4ZpFxTGlppCWijPb5T9bTpg9tndXUgxZ+8Iusk4Vm o7IvTCBgZd7VuKCb0Zw5Xn08LvlpLoHpw8Ts3iS9q1RU+69VDDLKM0eepskCzawiEl rXuEIPQaRFOug== Message-ID: <9199f28e-e2b7-48c8-b61f-0b787e322443@gaisler.com> Date: Fri, 23 Jan 2026 16:15:54 +0100 Precedence: bulk X-Mailing-List: linux-alpha@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 , will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, peterz@infradead.org, dev.jain@arm.com, akpm@linux-foundation.org, david@kernel.org, ioworker0@gmail.com, linmag7@gmail.com 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 References: Content-Language: en-US From: Andreas Larsson In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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 ... I bisected to this one on mm-unstable from approximately 2026-01-12. The warning is from /* Misaligned rcu_head! */ WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1)); in __call_rcu_common() and the unaligned accesses follows from there. Regards, Andreas