From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 99B79C43602 for ; Fri, 3 Jul 2026 09:33:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 700306B00B4; Fri, 3 Jul 2026 05:33:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6D7B16B00B5; Fri, 3 Jul 2026 05:33:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5EE216B00B6; Fri, 3 Jul 2026 05:33:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 2BA636B00B4 for ; Fri, 3 Jul 2026 05:33:03 -0400 (EDT) Received: from smtpin26.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 864308E484 for ; Fri, 3 Jul 2026 09:32:57 +0000 (UTC) X-FDA: 84946951194.26.4A0C8BD Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf02.hostedemail.com (Postfix) with ESMTP id 9F5B180005 for ; Fri, 3 Jul 2026 09:32:55 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=ewYhOz+y; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf02.hostedemail.com: domain of vbabka@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=vbabka@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1783071175; b=72JSZgxCjQ0tb0I2FmrZ148ut5BlHH94kbG31WuAI3nI43tb1ggSJPs4MGJM4hgDZSG/el bUwW+zxqzCt/51t59wMIKmeOCFZOvJogDnSKfkURcsl2io+JLIELEP+mkKBmh4pC/HLSDi w+h25QASuRUv2/amgQAdG/cH3uKd3HU= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1783071175; h=from:from:sender: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:dkim-signature; bh=e1pQpUBYSThfjFqXpi3CJbvoH2B8jgJGjXQchqDbIYs=; b=thv4soVoc4+g3VnOy7muMDaUXpMcVehj8eshizlNe+vnAeVjEG4hvbuPF+ORkuC/gGu9Z1 JoTNRCAuSoaKFS2qqaLLoMR0Nl0ucyUuW6DS0bv7Hk8LNqZdfXk+IOb98/ILe6aPR2/JcF bAkpLiByvTNiHPXHY6oX1enBqIyzm3g= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=ewYhOz+y; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf02.hostedemail.com: domain of vbabka@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=vbabka@kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id C746B41157; Fri, 3 Jul 2026 09:32:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1E1451F000E9; Fri, 3 Jul 2026 09:32:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783071174; bh=e1pQpUBYSThfjFqXpi3CJbvoH2B8jgJGjXQchqDbIYs=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ewYhOz+y/2ODJQiSe/1wYQEvPysmor5pP4hs4s16yHMRJct21kwF7eTWcwUsHq5jr xbKpyswZ71LI/axa/e7vJAaK0uyh+cN3GPhs4nDzG/9z77a4NzlfWMCzpiauiYyC0G otHE19G5VpTD58+dIcVh4xBBtQWZtj8UwN7J7hGJzkPc2cNMWok0Uxe6GXgGX/iaD0 K3rlzEMJQfO8x7gTe1qKW2vhOk3n7DxihnDmtl3zT1cBAZ4JVjdKyaU0sRMvsJSUnB xUDixob2C4kwpPJB6mdECWk7woRCVBU5gPDlX7xWq0KJFCmSgxI0fipNd6D+r8yfKu yuDeJKhf3eneQ== Message-ID: <1e162a97-1594-495d-b48e-7dafaa0a6d82@kernel.org> Date: Fri, 3 Jul 2026 11:32:46 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 18/18] mm: factor out can_spin_trylock() Content-Language: en-US To: Brendan Jackman , Andrew Morton , Suren Baghdasaryan , Michal Hocko , Johannes Weiner , Zi Yan , Muchun Song , Oscar Salvador , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt Cc: "Harry Yoo (Oracle)" , Gregory Price , Alexei Starovoitov , Matthew Wilcox , Hao Ge , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, derkling@google.com, reijiw@google.com, Yosry Ahmed References: <20260702-alloc-trylock-v4-0-0af8ff387e80@google.com> <20260702-alloc-trylock-v4-18-0af8ff387e80@google.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20260702-alloc-trylock-v4-18-0af8ff387e80@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: km7j39f1n3bqiq8p59d7b631w9nigm7s X-Rspamd-Queue-Id: 9F5B180005 X-HE-Tag: 1783071175-592854 X-HE-Meta: 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 yJg/VQ1r wYwm9isj2dXHdOKyXGKA9xsWdh2CJWkmPTyIILVqLIKxhd7a+2TmhDQSgYaHMqTyDnQdkeg41meI6zDYTSpn6GnLA0c35d5/MvKA+fUnmn0Rg++RKCshs4woALoahxppjcUa/PypEHJJT1KQKVr9CzFz5iFoVSaTlqk7dB9bTQp9iQjJAfiKoyH2azhEVV0PS26oRCDwhHQiVHa/0o/FUJQzoKxIA+jUx53HzgzXstjfr0epAoP0SyCMfLKKed7uP8SAp/C8HxLsUR/rCnOdiv48VYz45OoIcCnEvLj5C/TZoIOoqAguWGN8aCn4LDZrsqU+5LjREaQLM+4qoBSyL4T58BZvVP6Py5+Wdjt0NJbxEcgkA5xTzQBVHVW7A48hMtXQCRXwHYpvsCenpIYmTtCuhMj1Le2C3ZKg8Dnt8WoLCFWI= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/2/26 11:49, Brendan Jackman wrote: > Deduplicate checks for whether the current context is safe for > spin_trylock(). > > Does this function really belong in mm/internal.h or is it generic? Not > sure. If someone ends up duplicating this logic elsewhere in the kernel, > that would be a shame. But goes in some generic header, someone treats > it as documentation about where it's guaranteed safe to spin_trylock(), > and then it emerges that there are other subtle preconditions that > didn't affect the mm usecase, that would be worse. So, just be > conservative and keep it local. Agreed. We could even use page_alloc.h ? > Suggested-by: Harry Yoo > Link: https://lore.kernel.org/all/397859cb-b127-4cc6-9c71-044afc99bf0c@kernel.org/ > Signed-off-by: Brendan Jackman Reviewed-by: Vlastimil Babka (SUSE) > --- > mm/internal.h | 23 +++++++++++++++++++++++ > mm/page_alloc.c | 17 +---------------- > mm/slub.c | 10 +--------- > 3 files changed, 25 insertions(+), 25 deletions(-) > > diff --git a/mm/internal.h b/mm/internal.h > index 3c00eaf5f45a4..e6f300693ffd7 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -1715,4 +1715,27 @@ static inline void mm_prepare_for_swap_entries(struct mm_struct *mm) > } > } > > +static inline bool can_spin_trylock(void) > +{ > + /* > + * In PREEMPT_RT spin_trylock() will call raw_spin_lock() which is > + * unsafe in NMI. If spin_trylock() is called from hard IRQ the current > + * task may be waiting for one rt_spin_lock, but rt_spin_trylock() will > + * mark the task as the owner of another rt_spin_lock which will > + * confuse PI logic, so return immediately if called from hard IRQ or > + * NMI. > + * > + * Note, irqs_disabled() case is ok. spin_trylock() can be called > + * from raw_spin_lock_irqsave region. > + */ > + if (IS_ENABLED(CONFIG_PREEMPT_RT) && (in_nmi() || in_hardirq())) > + return false; > + > + /* On UP, spin_trylock() always succeeds even when it is locked */ > + if (!IS_ENABLED(CONFIG_SMP) && in_nmi()) > + return false; > + > + return true; > +} > + > #endif /* __MM_INTERNAL_H */ > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index c3b246e67ed14..a63733dac659e 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5291,22 +5291,7 @@ static inline bool alloc_order_allowed(gfp_t gfp, unsigned int order, > > static inline bool alloc_nolock_allowed(void) > { > - /* > - * In PREEMPT_RT spin_trylock() will call raw_spin_lock() which is > - * unsafe in NMI. If spin_trylock() is called from hard IRQ the current > - * task may be waiting for one rt_spin_lock, but rt_spin_trylock() will > - * mark the task as the owner of another rt_spin_lock which will > - * confuse PI logic, so return immediately if called from hard IRQ or > - * NMI. > - * > - * Note, irqs_disabled() case is ok. This function can be called > - * from raw_spin_lock_irqsave region. > - */ > - if (IS_ENABLED(CONFIG_PREEMPT_RT) && (in_nmi() || in_hardirq())) > - return false; > - > - /* On UP, spin_trylock() always succeeds even when it is locked */ > - if (!IS_ENABLED(CONFIG_SMP) && in_nmi()) > + if (!can_spin_trylock()) > return false; > > /* Bailout, since _deferred_grow_zone() needs to take a lock */ > diff --git a/mm/slub.c b/mm/slub.c > index 3989b4758ae0a..b19dc46de73c5 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -5408,15 +5408,7 @@ static void *__kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_f > if (unlikely(!size)) > return ZERO_SIZE_PTR; > > - /* > - * See the comment for the same check in > - * alloc_frozen_pages_nolock_noprof() > - */ > - if (IS_ENABLED(CONFIG_PREEMPT_RT) && (in_nmi() || in_hardirq())) > - return NULL; > - > - /* On UP, spin_trylock() always succeeds even when it is locked */ > - if (!IS_ENABLED(CONFIG_SMP) && in_nmi()) > + if (!can_spin_trylock()) > return NULL; > > retry: >