From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-174.mta0.migadu.com (out-174.mta0.migadu.com [91.218.175.174]) (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 D99763BED23 for ; Thu, 28 May 2026 12:59:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.174 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779973189; cv=none; b=GklBCnF2xxv6nOrEINt19S72ybnzkqKEtj10REsZ2H+ngvwG5wIwWovXePSA/uZWdBwza2jQJNq1ZhIDb7VbThJzNvuaGhxGL84eTzCVNwUKAez7r+PHBzD0lvYcjYwOgmVEEaxEJU8A3IK5+JjOcwI89gwhfzn11206BFB/iLo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779973189; c=relaxed/simple; bh=sIou1/uCXi+iGnp3M+/32mIuL66viWaxtFcS2RSdN1c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=C3l5ErdugTvR8PaQpdxN2xA/IOo1rDZwgYrzqW5MuPNcySUtrS859Wsr2NjGUMqE2rfm6KnAGO2jqvq8yCPgjewMEVIhHPAzoTtGgf1fVbRT0AAM6CfqfUP6O6B37xeFTOgnlzzECzZ5uNTbCB/nypGB0Bb4dgLFEPrLVfGtrIQ= 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=gEgOWBYl; arc=none smtp.client-ip=91.218.175.174 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="gEgOWBYl" Message-ID: <6ca2af4a-90ed-4d7e-9c21-42ebffddc3fe@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1779973183; 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=/7aIdks3CmcGjyyyeA3kszxapotlnaFMZvWoNmtYiZ8=; b=gEgOWBYleLfJ4o8TSg0b50sNALcy2gCscDl4hn9L3rEguhiBPhziUkl0d99DPhO9vrbiJA YW1cr5Ep5I+x6SCOT8z3GK/UPBroP4o1fdzutyJQgI702NZG5ifiEXWxWOJ0OmwG8O9ddc PPlposNDvM6/0Ynl+Tvu6F1gAfrF4uI= Date: Thu, 28 May 2026 13:59:37 +0100 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: =?UTF-8?B?UmU6IOetlOWkjTog562U5aSNOiBb5aSW6YOo6YKu5Lu2XSBSZTogW1BB?= =?UTF-8?Q?TCH=5D_mm/mempool=3A_use_static_key_for_boot-time_debug_enablemen?= =?UTF-8?Q?t?= To: "Li,Rongqing(ACG CCN)" Cc: Jonathan Corbet , Shuah Khan , Vlastimil Babka , Harry Yoo , Andrew Morton , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" References: <20260527104634.2434-1-lirongqing@baidu.com> <20260527130337.983366-1-usama.arif@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Usama Arif In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 28/05/2026 11:50, Li,Rongqing(ACG CCN) wrote: > > >> >> On 28/05/2026 04:00, Li,Rongqing(ACG CCN) wrote: >>>>> From: Li RongQing >>>>> >>>>> Replace the #ifdef CONFIG_SLUB_DEBUG_ON conditional compilation with >>>>> a static key (mempool_debug_enabled). This allows enabling mempool >>>>> debugging at boot time via: >>>>> >>>>> mempool_debug >>>>> >>>>> Instead of requiring CONFIG_SLUB_DEBUG_ON at compile time. Benefits: >>>>> >>>>> - Debugging can be enabled without rebuilding the kernel >>>>> - Uses standard kernel static_key mechanism with minimal overhead >>>>> >>>>> Suggested-by: Vlastimil Babka (SUSE) >>>>> Signed-off-by: Li RongQing >>>>> Cc: Vlastimil Babka >>>>> Cc: Harry Yoo >>>>> Cc: Andrew Morton >>>>> Cc: Hao Li >>>>> Cc: Christoph Lameter >>>>> Cc: David Rientjes >>>>> Cc: Roman Gushchin >>>>> --- >>>>> Documentation/admin-guide/kernel-parameters.txt | 5 ++++ >>>>> mm/mempool.c | 32 >>>> ++++++++++++++++++------- >>>>> 2 files changed, 28 insertions(+), 9 deletions(-) >>>>> >>>>> diff --git a/Documentation/admin-guide/kernel-parameters.txt >>>>> b/Documentation/admin-guide/kernel-parameters.txt >>>>> index 35ed9dc..5a070e6 100644 >>>>> --- a/Documentation/admin-guide/kernel-parameters.txt >>>>> +++ b/Documentation/admin-guide/kernel-parameters.txt >>>>> @@ -3998,6 +3998,11 @@ Kernel parameters >>>>> Note that even when enabled, there are a few cases where >>>>> the feature is not effective. >>>>> >>>>> + mempool_debug [MM] >>>>> + Enable mempool debugging. This enables element >>>>> + poison checking when freeing elements back to the >>>>> + pool. Useful for debugging mempool corruption. >>>>> + >>>>> memtest= [KNL,X86,ARM,M68K,PPC,RISCV,EARLY] Enable >> memtest >>>>> Format: >>>>> default : 0 >>>>> diff --git a/mm/mempool.c b/mm/mempool.c index db23e0e..4f429a1 >>>> 100644 >>>>> --- a/mm/mempool.c >>>>> +++ b/mm/mempool.c >>>>> @@ -16,11 +16,28 @@ >>>>> #include >>>>> #include >>>>> #include >>>>> +#include >>>>> +#include >>>>> #include "slab.h" >>>>> >>>>> static DECLARE_FAULT_ATTR(fail_mempool_alloc); >>>>> static DECLARE_FAULT_ATTR(fail_mempool_alloc_bulk); >>>>> >>>>> +/* >>>>> + * Debugging support for mempool using static key. >>>>> + * >>>>> + * This allows enabling mempool debug at boot time via: >>>>> + * mempool_debug >>>>> + */ >>>>> +static DEFINE_STATIC_KEY_FALSE(mempool_debug_enabled); >>>>> + >>>>> +static int __init mempool_debug_setup(char *str) { >>>>> + static_branch_enable(&mempool_debug_enabled); >>>>> + return 0; >>>>> +} >>>>> +early_param("mempool_debug", mempool_debug_setup); >>>>> + >>>> >>>> Can static_branch_enable() in mempool_debug_setup() run before >>>> jump_label_init() has set static_key_initialized? >>>> >>>> Looking at start_kernel() in init/main.c: >>>> >>>> setup_arch(&command_line); >>>> mm_core_init_early(); >>>> /* Static keys and static calls are needed by LSMs */ >>>> jump_label_init(); >>>> ... >>>> /* parameters may set static keys */ >>>> parse_early_param(); >>>> >>>> This will trigger the warning in include/linux/jump_label.h has: >>>> >>>> #define STATIC_KEY_CHECK_USE(key) WARN(!static_key_initialized, \ >>>> "%s(): static key '%pS' used before call to jump_label_init()", \ >>>> __func__, (key)) >>>> >>>> >>>> mm/dmapool.c registers an equivalent debug toggle via __setup() >>>> rather than >>>> early_param(): >>>> >>>> static int __init dmapool_debug_setup(char *str) >>>> { >>>> static_branch_enable(&dmapool_debug_enabled); >>>> return 1; >>>> } >>>> __setup("dmapool_debug", dmapool_debug_setup); >>>> >>>> I think you can reuse that. >>> >>> Thanks for your review! >>> >>> While this boot-time ordering used to be a generic issue, it seems >>> many architectures have already aligned or fixed this internally. For >>> instance, >>> >>> commit ca829e05d3d4 ("powerpc/64: Init jump labels before >>> parse_early_param()") and commit 6070970db9fe ("m68k: Initialize jump >>> labels early during setup_arch()") explicitly relocated jump_label_init() before >> the early parameter parsing. >>> >> >> I think 32 bit ARM doesnt? > > You are right, 32-bit ARM doesn't. > > However, the correct architectural approach should be fixing the boot sequence > inside arch/arm/ to match arm64 , powerpc and m68k, rather than compromising core MM > code with temporary boilerplate variables. > > I prefer to keep the mempool implementation clean. If ARM32 triggers the > warning, the proper remedy is a follow-up patch to align its setup_arch() > ordering. > > What do you think? > I think it would be a prerequisite rather than a follow up patch inorder to not break 32 bit arm. I will let ARM and slab maintainers decide on this.