From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f73.google.com (mail-ej1-f73.google.com [209.85.218.73]) (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 D3A384DB554 for ; Thu, 2 Jul 2026 09:50:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782985813; cv=none; b=b9epaZBIOZmEVNx4X4SnenLc/Z4uNElcPDUKujwJ+58Bxv312VJHBTeNs/yhUfoRe8hiSOt2iKZM2Vd8GyzMqtoZpPXKCBKN17knk8I5L/dAd+FH+toS2h+A/Wh5rC7Gx1jfQemVovnR6ErwReaQPggoOKUHvs2LhkZ2Dy9fdUo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782985813; c=relaxed/simple; bh=6lXyelhP+YzK5NOUKYSS01IIuo1QDayHo85EqH8ryQk=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Sr6v7PiEmbTmDE+pkXGWRxcLQa29GRRSs9TZQ8Qwu7QILBlvimY11d5+EnRPAI37RAZgwMR32WLMZ79qtXXaCbQfQupL72llwP9i41bEO1+QCXV7dJTySZUrL8TSZMiWNMtp2t3y8nJSKPRo054ndKRY+nOWzMEu9pDD3+kbQ04= 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=TnaAZCLu; arc=none smtp.client-ip=209.85.218.73 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="TnaAZCLu" Received: by mail-ej1-f73.google.com with SMTP id a640c23a62f3a-c11f0760aadso180610166b.1 for ; Thu, 02 Jul 2026 02:50:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1782985810; x=1783590610; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=TP8w64q3enZcalDNTlZcEsZaQVlvwCzoUrHNAb6H0EQ=; b=TnaAZCLu1P5jHml24oWn+15T7525MeCAzJrTqXCWitk4nc+aXsRTRrJBkKbCIYOMm/ n0EsolQU8qaWeKD9qfmbLJr0hk8vIxZgYBGl9VsTmSh95zsyiUXfG0nQqyrCNusHJkcW wwh+EsR4NUGpjpw5KT5iv1e2rarm0ZYrprr8ET7vb8COAxb9v2u/wcTe8CkYpLhQcSbH nq0lsLQgSH0KBxDGDGIBat+zsPdmU7bFhHZudq4TgZ6nJEZ1czUYs2wLjsYEqEKY9NSD 3kNXVF29UPtQqBs1FQkpDGsznNkPLfKZoL2b0DtV78mmT2xHye1cpPo2VDDT9YsmRUne /pHw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782985810; x=1783590610; h=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; bh=TP8w64q3enZcalDNTlZcEsZaQVlvwCzoUrHNAb6H0EQ=; b=SF2nTABx+IQW8Asl4/ATG0JH/HCBKY4pqHeqJoV57CedTPkvh+E1Q34mTPNohJkrds dwev4wH/eKNhJkiUrG9KnxpxBv0NGdYNpj7e2Q+O+XzUbgjAEQTHEPvvKaeOmJmrwv+d Zk/QzJa738rBeE+TGv+kAu9yWCO8H0BkJVb2UBorDU6J80ZlVnMjTSpNRWokwoKoIP1O /zulNxfufeVgiDKAN/wqcC7sIVUzmyRzBIjQ/w8UBGT4hM+UKoResVV8xGFXxElZZTLS qV7K2mQf3OV5bTmufwPzN0hMyZaCzJTbdQkUDcXdM2ZLDes3GigLW8pw+RrUPmXapGl2 Ry3Q== X-Forwarded-Encrypted: i=1; AHgh+Rr3snQkBHxycArpf9bmcXySfql6z+ejPSpOnWBY3aF3cOCtRJ6OMkQiLNjaloP8tjVPO8A+78CI396gN88=@vger.kernel.org X-Gm-Message-State: AOJu0YypHJgi6p234kR9/IcVTGOEzngMqxsjmoNwA9kZVpYLprg6jdzQ psQyLpPtjJ5u5RsWp8rtWaZOQg7rknmvfLmJBItjaF/1dYnLIAcYj7vJblZqooJSsFDX1oAfyiL GRvtWbIybJMA/6g== X-Received: from ejiv19.prod.google.com ([2002:a17:906:2f13:b0:c12:6b9c:5e58]) (user=jackmanb job=prod-delivery.src-stubby-dispatcher) by 2002:a17:907:e117:b0:bfb:1e1c:3197 with SMTP id a640c23a62f3a-c12ae7ba8e9mr187344066b.41.1782985809984; Thu, 02 Jul 2026 02:50:09 -0700 (PDT) Date: Thu, 02 Jul 2026 09:49:49 +0000 In-Reply-To: <20260702-alloc-trylock-v4-0-0af8ff387e80@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260702-alloc-trylock-v4-0-0af8ff387e80@google.com> X-Mailer: b4 0.15.2 Message-ID: <20260702-alloc-trylock-v4-18-0af8ff387e80@google.com> Subject: [PATCH v4 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 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/ 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 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: -- 2.54.0