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From: Paul Walmsley <pjw@kernel.org>
To: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
	 Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	 Alexandre Ghiti <alex@ghiti.fr>,
	linux-riscv@lists.infradead.org,  linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH] riscv: Use an atomic xchg in pudp_huge_get_and_clear()
Date: Fri, 19 Sep 2025 19:39:43 -0600 (MDT)	[thread overview]
Message-ID: <c8afb3b4-e5d5-628b-6bce-0b1b3137a667@kernel.org> (raw)
In-Reply-To: <20250814-dev-alex-thp_pud_xchg-v1-1-b4704dfae206@rivosinc.com>

Hi Alex,

On Thu, 14 Aug 2025, Alexandre Ghiti wrote:

> Make sure we return the right pud value and not a value that could
> have been overwritten in between by a different core.
> 
> Fixes: c3cc2a4a3a23 ("riscv: Add support for PUD THP")
> Cc: stable@vger.kernel.org
> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> ---
> Note that this will conflict with
> https://lore.kernel.org/linux-riscv/20250625063753.77511-1-ajd@linux.ibm.com/
> if applied after 6.17.

Two quick questions on this one:

- I see that you're using atomic_long_xchg() here and in some similar 
functions in pgtable.h, rather than xchg().  Was curious about the 
rationale for that?

- x86 avoids the xchg() for !CONFIG_SMP.  Should we do the same?

thanks,

- Paul


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  reply	other threads:[~2025-09-20  1:40 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-08-14 12:06 [PATCH] riscv: Use an atomic xchg in pudp_huge_get_and_clear() Alexandre Ghiti
2025-09-20  1:39 ` Paul Walmsley [this message]
2025-09-22  6:19   ` Alexandre Ghiti

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