From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-101.freemail.mail.aliyun.com (out30-101.freemail.mail.aliyun.com [115.124.30.101]) (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 2607812B94 for ; Thu, 15 Jan 2026 10:00:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.101 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768471249; cv=none; b=e8ivOfPJi4ByuLBpLdLKTM5zAwhtcJrP1v3F1zEplqSTiWcyk+0rkslmvcqw1SpDYcj8mGi0kKco02Ef/RTEVRpG18whD/5XGdZrwA2T72ZYM8IEeWN/9B9vqKgoLl5nQawOD3P5dNh4KvG5CGTx4DxfJGl4NzLlObZj7UPazQk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768471249; c=relaxed/simple; bh=BR5WFrGBomKzTjAl8OncfG5uY9SA3RywQ1OnsSNF92I=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qHC6G0LSQ1T/26feVOG3tArSin+Jh2xk3fpb8fVfgvDwlo5ooMlevv/6iOgGlGS6y083e7C7wapOWHaRuTzN5vyImhayZpvNooxVUxsluRyO+tn+GyqCbtqAQOLIXFB/vTnVtiEOaJ1zZvwFhddy/TH0BArq3dZkcWLPN5vv13Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=SqKpnbUv; arc=none smtp.client-ip=115.124.30.101 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="SqKpnbUv" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1768471239; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=Ya8nAi114rbQsSwtfqViDZqZMj68VQCcDvy2eEcJ3Es=; b=SqKpnbUvrTlOrtYA394MlD2etxRRHL7NWDaypDk2aAmzeilQFh8balCK+WRy+tX8xtzrbMPp41BNHaxNki4vBm6cNFEvFx+ZxxbZpHPNqlICepl+eNtXAtYB8qdb95ngaw9aMCKBufY8KXJcCzImHei0wvgaJWBxlrk6L8yz+E4= Received: from 30.74.144.130(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0Wx68Cip_1768471236 cluster:ay36) by smtp.aliyun-inc.com; Thu, 15 Jan 2026 18:00:37 +0800 Message-ID: <0bc3807e-2c1b-43af-9aab-665ce30d49d4@linux.alibaba.com> Date: Thu, 15 Jan 2026 18:00:36 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/1] mm/khugepaged: move tlb_remove_table_sync_one out from under PTL To: Lance Yang , akpm@linux-foundation.org, david@kernel.org Cc: ioworker0@gmail.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, ziy@nvidia.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260115071651.42626-1-lance.yang@linux.dev> From: Baolin Wang In-Reply-To: <20260115071651.42626-1-lance.yang@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Lance, On 1/15/26 3:16 PM, Lance Yang wrote: > From: Lance Yang > > tlb_remove_table_sync_one() sends IPIs to all CPUs and waits for them, > which we really don't want to do while holding PTL. Could you add more comments to explain why this is safe for the PAE case? For the non-PAE case, you added a new tlb_remove_table_sync_one(), why we need this (to solve what problem)? Please also add more comments to explain. > Just move the call to after we release PTL, and drop the macro wrapper > while we're at it. > > Signed-off-by: Lance Yang > --- > include/linux/pgtable.h | 4 ---- > mm/khugepaged.c | 5 +++-- > 2 files changed, 3 insertions(+), 6 deletions(-) > > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h > index eb8aacba3698..fb04ed22052c 100644 > --- a/include/linux/pgtable.h > +++ b/include/linux/pgtable.h > @@ -755,7 +755,6 @@ static inline pmd_t pmdp_get_lockless(pmd_t *pmdp) > return pmd; > } > #define pmdp_get_lockless pmdp_get_lockless > -#define pmdp_get_lockless_sync() tlb_remove_table_sync_one() > #endif /* CONFIG_PGTABLE_LEVELS > 2 */ > #endif /* CONFIG_GUP_GET_PXX_LOW_HIGH */ > > @@ -774,9 +773,6 @@ static inline pmd_t pmdp_get_lockless(pmd_t *pmdp) > { > return pmdp_get(pmdp); > } > -static inline void pmdp_get_lockless_sync(void) > -{ > -} > #endif > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 9f790ec34400..0a6cebf880e0 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1664,10 +1664,10 @@ static enum scan_result try_collapse_pte_mapped_thp(struct mm_struct *mm, unsign > } > } > pgt_pmd = pmdp_collapse_flush(vma, haddr, pmd); > - pmdp_get_lockless_sync(); > pte_unmap_unlock(start_pte, ptl); > if (ptl != pml) > spin_unlock(pml); > + tlb_remove_table_sync_one(); > > mmu_notifier_invalidate_range_end(&range); > > @@ -1818,7 +1818,6 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) > */ > if (likely(file_backed_vma_is_retractable(vma))) { > pgt_pmd = pmdp_collapse_flush(vma, addr, pmd); > - pmdp_get_lockless_sync(); > success = true; > } > > @@ -1826,6 +1825,8 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) > spin_unlock(ptl); > drop_pml: > spin_unlock(pml); > + if (success) > + tlb_remove_table_sync_one(); > > mmu_notifier_invalidate_range_end(&range); >