From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-180.mta0.migadu.com (out-180.mta0.migadu.com [91.218.175.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6A254230270 for ; Mon, 26 Jan 2026 07:00:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769410811; cv=none; b=i6ZWYLUzdkgRjxTbqJhhYicMMQPYib4JHfl1HNxjgJMem/EgK3LyNEj9+lYvhyXK5xdWhuykn6drPxMXl9ZPj/4b8RRcpdrNwSId6khqTwgWB19o1EzGOcQkeWKV0dxoT/gXYDrXqmP7zcHWNuoIZjON/2+7bcsmbWiQqhiNYKw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769410811; c=relaxed/simple; bh=hIVMICCOrwOEHb7O10TcOjpQqCQ90wHru/xyyTPnNZQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Q4KuvnPXdH8/+pJDOTQXCLSG9gQw1EEgiw7TypzgLEKDdkEVHcGczkqXfE51AFD/FvUQ/NIWa/4O9lge863pp3cyabiSKPZyGMoiJowaOQDg/sMkXroZfaCI12iHopqMzD08K4QJHAhLkuFOdA7DYfBnAX4aiAWMLUdOvrboZz8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=io0Jn+3N; arc=none smtp.client-ip=91.218.175.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="io0Jn+3N" Message-ID: <646d9b5c-453c-4db8-b578-0f343e170379@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1769410802; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hybAGJDtwUTQyBJLSE6cgT3x4CprzyvIGdy1i62DoMg=; b=io0Jn+3NajuPHPI4XjqNt9sYHPn2FyPfP/1eLMYG5oEK9p8YQ2ayv0ii4eZsQi7AY5Kxh/ 8bRt82NClUXSKr1V31d6I/GqCfQd+DB4Ux8EDoCg31zgpyKNNatRAU/WP75QWfFgYjHG7n Oc4aJiIqhIpd+iDcwrxRH5wDMzgILbU= Date: Mon, 26 Jan 2026 14:59:43 +0800 Precedence: bulk X-Mailing-List: linux-alpha@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v3 7/7] mm: make PT_RECLAIM depends on MMU_GATHER_RCU_TABLE_FREE To: Andreas Larsson , david@kernel.org 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> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: <9199f28e-e2b7-48c8-b61f-0b787e322443@gaisler.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT 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: __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? Thanks, Qi > ... > > 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 >