From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f73.google.com (mail-wm1-f73.google.com [209.85.128.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8FACB3D75A9 for ; Fri, 3 Jul 2026 12:32:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783081968; cv=none; b=DCE3kyc4RO9qFT8bubzQw6Efb1kilMSvSPSfAOodhtJIoqpm4CB9FvVQtvezonHCsPaQGhkFWterzR8qkzEB0kpZvbDQZHacoXwFRlYTHwII7Rx7HLoxfJFnvZa5O/CKEs1V1i+wzTwAILJwHumzKNk54ctyqo4KDijF2oHS3EE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783081968; c=relaxed/simple; bh=cbhrnwky3M1OQ4/1gR5owBLQRKaVFV0YFMBztYNU3MQ=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=ZI5wo+ft/FLL9lqR5fEImBd9UzndOKJXqwHEws0YcEBoNhYPvBHW0jlUALirg04NPUeVUWZp90XZ/uFQbH+Hu739u6BX6iqoeQAIL8masUDrxgZ+zjxif1QEJksuDJR8QJB7Ezg+zuEsCHBuzMOex66Cwf6NElWmYL25SQGkgoc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jackmanb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=bOpDkz0j; arc=none smtp.client-ip=209.85.128.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jackmanb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="bOpDkz0j" Received: by mail-wm1-f73.google.com with SMTP id 5b1f17b1804b1-493ba771d1bso4943205e9.2 for ; Fri, 03 Jul 2026 05:32:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1783081962; x=1783686762; darn=lists.linux.dev; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=qmGplZPZ08UUT4GJp4VHEL7joXJ434YzWEyzXagN1Q8=; b=bOpDkz0jN1yVHXz74p9xakQKO9/Gy3S2RNpAb8ljvsq4sTC03oOQxb1PR6bMmAy/kP olP6qw4Ge3RP7BuDbDDuWxNwVgUmj+Ca6cHJygi9ySmuPZb1C0n3dS3ZIhF4JZRclVPf obpgnTfFQt8YFE4l6B3NrzfKIxD55romjdg4LgPZILYJDsBIJo2PVMSTMNqQzHyhOzqh TQGR7TmcC53gmIfGnTjwkAK8iwIFBTQScizdPslQiURRsDAB+xOKOxs0LI3agEd5XtA7 iN/G5/a27ytNqUC2tTnoLo2pulATY/EvGzpVuLmUcjoECShxan6SMZet5T6IYP3MM5ku DsIQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783081962; x=1783686762; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=qmGplZPZ08UUT4GJp4VHEL7joXJ434YzWEyzXagN1Q8=; b=Pd72uMpeG9+7zApEba2ADCxkifw9Qed/Q00wh8t9ronLg4C2iVUvJjtbc1AwcoF8L7 CuL90JuEOIUMBq/Zvm7ERtAR6Qg2jYrTvBqPCbMvcdz40rnQjebP7QlWTGXIFg2kdSVc qlOXXf16OBCbufIc/Qn+UzZqsMDw8sFaAHz31Ip8K1Y2pPUmDBSuDOYkNtzNF3KOb0Td fQ6nhTNKV1B6jz4NyvPNUvIjl/3VX3QeR/oDokqBn+oEHdM2KXt8dzP8KzENPVRNBeo0 uFEzrjFmKaxtNTIaKso+QVfYrRGLbm3kJFYT9wv8KdeEL1T6oabVnFEXvyFNMV9qJUNF f2wQ== X-Forwarded-Encrypted: i=1; AFNElJ8ZDc3ilvBIDWf6eVFKqheEosqkhNi+KS9kxqGYQBODM9wj9zk+5odKOTRKWovCdXqN6AFFI8alQ4gbXoEkwQ==@lists.linux.dev X-Gm-Message-State: AOJu0Yw78Ryaw4zAJ/I5uSbY3PjqbHVfh5KTtIhm23kxFxogFms7ReZP nW5LkOLC0XeY8A36FdaXW3bDPeqPF3QmKB07yMP5jOMxQ0mtYuJ5Opl7Dv07LdegMQerruSSaz5 jKLOsmxrqyCAw1w== X-Received: from wmok15.prod.google.com ([2002:a05:600c:478f:b0:493:b78f:716b]) (user=jackmanb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:35d2:b0:493:c3f9:65a2 with SMTP id 5b1f17b1804b1-493c3f9664bmr156103915e9.5.1783081962154; Fri, 03 Jul 2026 05:32:42 -0700 (PDT) Date: Fri, 03 Jul 2026 12:31:58 +0000 In-Reply-To: <20260703-alloc-trylock-v5-0-c87b714e19d3@google.com> Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260703-alloc-trylock-v5-0-c87b714e19d3@google.com> X-Mailer: b4 0.15.2 Message-ID: <20260703-alloc-trylock-v5-18-c87b714e19d3@google.com> Subject: [PATCH v5 18/18] mm: factor out can_spin_trylock() From: Brendan Jackman To: Andrew Morton , Vlastimil Babka , 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 , Johannes Weiner , 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, Brendan Jackman , Yosry Ahmed Content-Type: text/plain; charset="utf-8" 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 if it 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. Suggested-by: Harry Yoo Link: https://lore.kernel.org/all/397859cb-b127-4cc6-9c71-044afc99bf0c@kernel.org/ Reviewed-by: Vlastimil Babka (SUSE) Reviewed-by: Harry Yoo (Oracle) Signed-off-by: Brendan Jackman --- 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 7e3b2386e274b..0ae6ad2265125 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1716,4 +1716,27 @@ 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: -- 2.54.0