From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 2CC70395723; Thu, 22 Jan 2026 20:55:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769115327; cv=none; b=BOdSQisQ30732lhq4JcvpiZ7HD5kw23f8eaC2Xwclc3hDR6j5GJ56IUQekr2YWPL7w8qIXeqbyUpDXFGIpcfAHdm9x5Ymi+RBwE2xdtT3nMGzIVEUZ6GiAD+HlhycN3Hu0n8cWlpRc30idr34AVhVrHsWDsbiJnryVLO0Vh79VY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769115327; c=relaxed/simple; bh=3RonE8sCwdveY09Rm5eaaBB5Ddd2WM38NcpvZaK6rFI=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=cxL0z0ksffMlzkzO0IdM6ynxuUxM+1SPLDRDVaiy8WXMGAuZwcydGDTEQ/LnWntk4mmd1bMIpp3LoS3UsvHPh7DGNFVsYZQVorhZUANGYW52e0zgOmkDIJgiwf1Qv0BN6IhGfZMyuGWDyk6+TXfJM7suJmAcgg1yZRgRX6LO+t4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=orX3vY6N; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="orX3vY6N" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 03EE2C116C6; Thu, 22 Jan 2026 20:55:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1769115325; bh=3RonE8sCwdveY09Rm5eaaBB5Ddd2WM38NcpvZaK6rFI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=orX3vY6N+v2bBEqJf/x3rBu+MQkrbKH76zrEvIeO/Ltd+mJYqg+/KAwuVnrgGQyjy sErY3D3bSldRFWNzww9AlX2XJ+MDHT0VA5lGqETZEIxkdkDCUeHo+MGL3SB67con2U 9FEV4KOcq6NEqSw801uDKbVTutkHYIYCWpzetXqQ= Date: Thu, 22 Jan 2026 12:55:29 -0800 From: Andrew Morton To: Suren Baghdasaryan Cc: Lorenzo Stoakes , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Michal Hocko , Shakeel Butt , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt Subject: Re: [PATCH v3 06/10] mm/vma: clean up __vma_enter/exit_locked() Message-Id: <20260122125529.1f4a1806fd918155e0a5824b@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 22 Jan 2026 12:15:20 -0800 Suren Baghdasaryan wrote: > > + /* vma should remain attached. */ > > + if (locked) > > + WARN_ON_ONCE(__vma_exit_exclusive_locked(vma)); > > I'm wary of calling functions from WARN_ON_ONCE() statements. If > someone decides to replace WARN_ON_ONCE() with VM_WARN_ON_ONCE(), the > call will disappear when CONFIG_DEBUG_VM=n. Maybe I'm being paranoid > but it's because I have been bitten by that before... Yes please. The elision is desirable if the function has no side-effects, but __vma_exit_exclusive_locked() changes stuff. Someone(tm) should check for this. A pathetically partial grep turns up plenty of things: mm/slab_common.c: if (head && !WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&head_gp_snap))) mm/slab_common.c: if (!WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&bnode->gp_snap))) { mm/page-writeback.c: WARN_ON_ONCE(atomic_long_add_return(delta, mm/page_isolation.c: WARN_ON_ONCE(!pageblock_unisolate_and_move_free_pages(zone, page)); mm/page_alloc.c: VM_WARN_ONCE(get_pageblock_isolate(page), mm/numa_memblks.c: WARN_ON(memblock_clear_hotplug(0, max_addr)); mm/numa_memblks.c: WARN_ON(memblock_set_node(0, max_addr, &memblock.memory, NUMA_NO_NODE)); mm/numa_memblks.c: WARN_ON(memblock_set_node(0, max_addr, &memblock.reserved, mm/zsmalloc.c: WARN_ON(!zpdesc_trylock(zpdesc));