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 0C832CCD195 for ; Wed, 15 Oct 2025 18:52:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 558CF8E0086; Wed, 15 Oct 2025 14:52:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 530CC8E000C; Wed, 15 Oct 2025 14:52:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 41F668E0086; Wed, 15 Oct 2025 14:52:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 2D42B8E000C for ; Wed, 15 Oct 2025 14:52:31 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id B599714028E for ; Wed, 15 Oct 2025 18:52:30 +0000 (UTC) X-FDA: 84001244460.20.A4DA367 Received: from mail-wm1-f50.google.com (mail-wm1-f50.google.com [209.85.128.50]) by imf08.hostedemail.com (Postfix) with ESMTP id E266216000F for ; Wed, 15 Oct 2025 18:52:28 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=haZ7Sr4R; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf08.hostedemail.com: domain of vishal.moola@gmail.com designates 209.85.128.50 as permitted sender) smtp.mailfrom=vishal.moola@gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1760554349; 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=NwQCNOMiVNhviDLYmWNQR++Wsx+PX0Dsjg6jZ0iSZ8c=; b=uB9iWqRRHAZXY+DatCzhro7UO5+fSzRp+saiskswbx7PGEkySjktzu3wva3ZL6VWgkaSlE PgfZOUc9UHDUncEAkgQUaYPb5DLbESllXJMm3jCXECHEBGSEYxxFOekagU7LOT3uMmGKPW IqWhELWgM6wsx+RNTDKFRWmXBxHFJqk= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=haZ7Sr4R; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf08.hostedemail.com: domain of vishal.moola@gmail.com designates 209.85.128.50 as permitted sender) smtp.mailfrom=vishal.moola@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1760554349; a=rsa-sha256; cv=none; b=lM0NuQy2csT1dW3iciQ7QHtLYlkXrNER1Re+9y6UJ+iGDhdILNrMstOxDZH5bH3ADoiivv kz0HzEdU558cXot7q4EVro6RxEejWHptdf0IWiUvS3Z4lycPrBrz4l3xx+94qvGJAzY1U/ TaqOC8+sLpsj0ZV+mElimwgsp2voFII= Received: by mail-wm1-f50.google.com with SMTP id 5b1f17b1804b1-46e6c8bc46eso46740835e9.3 for ; Wed, 15 Oct 2025 11:52:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1760554347; x=1761159147; darn=kvack.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=NwQCNOMiVNhviDLYmWNQR++Wsx+PX0Dsjg6jZ0iSZ8c=; b=haZ7Sr4RPBt7AHOQQKRsH8udKXkqik7dtwMy675TXZnVlexc0zFgkaLhrq+b1Xlqpm ZaWp92usnBNSH26ILDT5Hdp9w5YtFNNgsmtwFHHhdPVg1dHNYvW/tkob9/DNxj2nWGfG xdtb+zBkGn5LR8gPv6vYL5OxwdyUAxLRoYgnwMZdsf9FHMW/z4HRhzkWYIxVjTBHJ7dv OKjndKTHjAJM6kVVauusR5lI8IXkqLnsfEFes5YD7shXdz9SWCeGj5xn9vHUGdYwMBa1 +yaD/9Z4QBEsuZeU8YpNzZkdB/llTcih0+sSXKDZg0Hp2x/rl0Tk1pf1s1VvnMecGhr3 GN/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760554347; x=1761159147; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=NwQCNOMiVNhviDLYmWNQR++Wsx+PX0Dsjg6jZ0iSZ8c=; b=WcpkvYVDgNEPNtzkStkz8sheSppJY7li4GVvwZhWlBbdI7mrHNdhSjoo0WovAdIoQY 8ZokRsAUlHba8RSlkhMUYPxyCQQrys7OwHy4wGmxEaKTUNaiEOLdLReeqsrYGNoki5/p 6zOB2aeRQO+tU9vNEUQG1R4LKb5oSc+p28MILG18cEs3izlX9f8hdjNFhZEn4aJQZ4zZ kuHZ/jq7su5Z8e+0GgVCH9hmltthUT+fCu21pTpfQZwMBP3iA1u0Ekp9cBrElX8z/I53 tu4PN9nDtwh96nDXbNuUYSKuGm1yQxmJPfxWfZEWsoYlXoS9auOycQMzvl1A61+92c/l OHyg== X-Forwarded-Encrypted: i=1; AJvYcCWLJazbGql7G8Vk95gJyP7linmKSi/NYAEps1isQkNMt6hcTg/KqvYAJQ1h+E2gJtqke1ICAoED+g==@kvack.org X-Gm-Message-State: AOJu0YxY1pTzgdguXBKiyRDjyK3XylSP2Ki344q4z+tgTqBopBtQa/Q2 bRyhhZdpBSZzD70vVrM7MnWSgqHIEy1gyf6UUZdTs/QIqZKeYT1vGQpQ X-Gm-Gg: ASbGncsGxn9SVREw6+F3LRu9Zrf2FYil2MJIvOxCCKAmQfSwS5kzXLQlz9RL/6XNSwu l+deUFxtxPE9of3a0nkc3rLt44du++AxrFFu/uhiCQAiy6PNoxizOOJZgCJ2N+dapflvkADThpV 4csqCzzyXDU8ChkGLs6i9zju3hs+MOSjlm+1f2EIrBIhbNPP4lPsTMg+trQM7VIoQvHGQ4xBjCO EmP1cW4a92ttCZuQLPPVPMc60FMOMr2yt9J7f6SkAyyl+RmhNo/ynbfgXS1rS0638g6H4Wf4P2W lBVzSh2uNlKbwQTx5PRDgX4xThSZNiGmT+HoFEh6LzSWrVuilg2ecHx5nDsZcSqF+C1mtIUpKy9 y7Xn7rAAKrPmJOj8gmMCpK/DPK9E9DS170CssjrG2uPjB6A== X-Google-Smtp-Source: AGHT+IFfn9/XhYNsg9kEBy3HRPWyVtIjr2aUR9s4v6atPJEbesiw2bkGCZdPCRugezv9LVZwavljTA== X-Received: by 2002:a05:600d:41f3:b0:46e:6603:2a84 with SMTP id 5b1f17b1804b1-46fa9b08bd7mr240557805e9.32.1760554347187; Wed, 15 Oct 2025 11:52:27 -0700 (PDT) Received: from fedora ([31.94.20.38]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-426ce57d3desm30688069f8f.7.2025.10.15.11.52.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Oct 2025 11:52:26 -0700 (PDT) Date: Wed, 15 Oct 2025 11:52:24 -0700 From: "Vishal Moola (Oracle)" To: Thomas =?iso-8859-1?Q?Wei=DFschuh?= Cc: Vlastimil Babka , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: Re: [PATCH] mempool: clarify behavior of mempool_alloc_preallocated() Message-ID: References: <20251014-mempool-doc-v1-1-bc9ebf169700@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20251014-mempool-doc-v1-1-bc9ebf169700@linutronix.de> X-Rspam-User: X-Rspamd-Queue-Id: E266216000F X-Rspamd-Server: rspam03 X-Stat-Signature: e71aioszpf4ut6rkgycohrhzzsxdhhsa X-HE-Tag: 1760554348-777059 X-HE-Meta: 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 lY73R9k+ PWGoa+twvvN62bYgPRoU88YjRqWvXArV7CGGetYjIpdjVZEI8kDakUgIi5wrKz7Z7Cw3WinwwR1h9USqRqy3IgpATnQPqiO+/cJN13u33kfKMOqla/tXkG7QR1Re4aKvwjLSf X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Oct 14, 2025 at 02:17:23PM +0200, Thomas Weißschuh wrote: > The documentation of that function promises to never sleep. > However on PREEMPT_RT a spinlock_t might in fact sleep. > > Reword the documentation so users can predict its behavior better. > > mempool could also replace spinlock_t with raw_spinlock_t which doesn't > sleep even on PREEMPT_RT but that would take away the improved > preemptibility of sleeping locks. > > Signed-off-by: Thomas Weißschuh > --- > mm/mempool.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/mempool.c b/mm/mempool.c > index 1c38e873e546fadcc594f041874eb42774e3df16..cceb09b75ebe35f263a5fb95ff6d400221ecbdd5 100644 > --- a/mm/mempool.c > +++ b/mm/mempool.c > @@ -461,8 +461,8 @@ EXPORT_SYMBOL(mempool_alloc_noprof); > * mempool_create(). > * > * This function is similar to mempool_alloc, but it only attempts allocating > - * an element from the preallocated elements. It does not sleep and immediately > - * returns if no preallocated elements are available. > + * an element from the preallocated elements. It only takes a single spinlock_t Might it make more sense to say "It may sleep" instead of "takes a single spinlock_t"? I feel like the fact that we take a spinlock isn't the important part here (especially because we always drop it before returning). > + * and immediately returns if no preallocated elements are available. > * > * Return: pointer to the allocated element or %NULL if no elements are > * available. > > --- > base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787 > change-id: 20251014-mempool-doc-625dd4996110 > > Best regards, > -- > Thomas Weißschuh >