From nobody Mon Feb 9 15:59:16 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D554422FF4C; Thu, 8 May 2025 23:42:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746747753; cv=none; b=mqWff8zkvCEBW/xZebpu5rz8fFwCgE58LDw/Xu7JRgIVD856EBbsIr4YGUEqbNj25qWYL2utQYyNz+OIC0oMYXEeJCaXNOURKHNnGdGTXWZqyaHSZxB1cSsPP5/RU2oeYXuJoVbxIJg9RQ6FWuR2PVWB4D6kibUkE7CYmXrGVnA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746747753; c=relaxed/simple; bh=AXbdvbhnhQJc2Vt4aBypgEAuD+IUYP3v+j6U5ZNRkMo=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=WVKVzNW7fYIwEZsn2WlmmkY33aF5mnVoXKf2aQYXEsWV9Duotsn5ccgGg0x9ByRukbvUnaSDv23wHf2Whm/rc/YfCfp8qSpbdWGUlAN+4O/2apxp73c6TQIarB5qBxFqceRQdgWfgfEB8VW9KJ3+0GefyljgPmjgw1WPpYH8PIA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=h9Bv20uA; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="h9Bv20uA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 615E3C4CEED; Thu, 8 May 2025 23:42:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1746747753; bh=AXbdvbhnhQJc2Vt4aBypgEAuD+IUYP3v+j6U5ZNRkMo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=h9Bv20uA1jdWwdjcX3Gn9YaMZTWfEcwAD19ooiJq3rMjC1JloCJ9b61oiCTJH6hMW bfwJXfloeE3BIUjDj4uELWtDivqP7NB+8dtebzMVHBeFMnHszMlGI39HQfQgXb3DTP v6CM7vRyw4CwvWaIYABjt74Yc2N+fp1A3GVkY8SSHz92zm3p8VQVRI55Jd8JLhm9Qj QpmjFAZE9Q0tojXwn255eN2UqcLWYGXV7vXmIGGDuyUzpOPzmRE79ifrTebZQ/wZ9q t9mXwDtJjMHytbbHPWSixYfCCVD8toYZU5/mSFT9v927Um/obXZwabnBk7HEyrzlDE nJ4zxenk2NuAA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 0D9D0CE11D3; Thu, 8 May 2025 16:42:33 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" Subject: [PATCH 2/3] rcutorture: Reduce TREE01 CPU overcommit Date: Thu, 8 May 2025 16:42:29 -0700 Message-Id: <20250508234230.1996554-2-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The TREE01.boot nr_cpus kernel boot parameter has been set to 43 for more than seven years, but it can cause RCU CPU stall warnings on arm64, most of the time involving the stop-machine subsystem. This should not be too surprising, given that this causes 43 vCPUs to spin with interrupts disabled when there are only eight physical CPUs. The point of this CPU overcommit is to test the ability of expedited RCU grace period initialization to handle races with incoming CPUs that have never previously been online. But limiting to 17 CPUs instead of 43 allows time for this code to be exercised, and eliminates (or at least greatly reduces) the incidence of RCU CPU stall warnings on arm64. So this commit therefore sets nr_cpus=3D17 in TREE01.boot. Signed-off-by: Paul E. McKenney --- tools/testing/selftests/rcutorture/configs/rcu/TREE01.boot | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE01.boot b/t= ools/testing/selftests/rcutorture/configs/rcu/TREE01.boot index 40af3df0f397f..1cc5b47dde282 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TREE01.boot +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE01.boot @@ -1,4 +1,4 @@ -maxcpus=3D8 nr_cpus=3D43 +maxcpus=3D8 nr_cpus=3D17 rcutree.gp_preinit_delay=3D3 rcutree.gp_init_delay=3D3 rcutree.gp_cleanup_delay=3D3 --=20 2.40.1