From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-52.mta1.migadu.com [95.215.58.52]) (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 0C86F34D397 for ; Sun, 18 Oct 2026 02:51:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792291884; cv=none; b=c+AhvEwAKbfF4hSlggr8qbmKKu8OhMtXQFuLA5necVnmvxaXUK50mI1Zr+sSJGHm334b76fCKdy+G7mspKWvDMz7KKXeAYWiv+mNbBqRidaVYiHDJLzuzImzOf2GCEbNKVemwmGefVuYSiSAyTLUz8pM9Fgdfc8NEoQ4Tgjgolg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792291884; c=relaxed/simple; bh=wA3bzBzkubJAzxoEJdPOpOYuFRmZFkX99276xQziAVA=; h=MIME-Version:Date:Content-Type:From:Message-ID:Subject:To:Cc: In-Reply-To:References; b=miUwLz2xAdMyaR9a0f7znIeqGMUj69/n1DsF6R7ZjxtpLTjxHegTpkL8C0+xxDwshedLdqN1c9WrZLvkSaJ16WXzAQijgkF3wO5LOqg/sfUr/BBsagG0zwo18UHjaNTAAXlssnVeW6qR7M5Ej1muCBYVrJmmrP1vMcTWITfKkM4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=MnU3EdKy; arc=none smtp.client-ip=95.215.58.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="MnU3EdKy" X-Envelope-To: rcu@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=wA3bzBzkubJAzxoEJdPOpOYuFRmZFkX99276xQziAVA=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1792291880; v=1; x=1792896680; b=MnU3EdKyeVTIpC3+eQ988IJXNZMz/Jm0PREQ+rp4JZffONKoIWu55eM+hF+NpqM5PgA6yC0L HcOP2hfurGFT03LCUeXMDBnwjcvOydo4RTITN7UVVvlJYtkWj+msy0Cafaf9cNIh85JaBCzrW1n Lzh2NHbfcX5HcAYJuXTHCVzg= X-Envelope-To: rcu@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id dd522225debb44ed; Sun, 18 Oct 2026 02:51:20 +0000 X-Mizu-Trace-ID: dd522225debb44ed X-Migadu-Flow: FLOW_OUT Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Sun, 18 Oct 2026 02:51:18 +0000 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: "Zqiang" Message-ID: <0c9fd241b8bdef73b3fe83683a238ad7df13bf65@linux.dev> TLS-Required: No Subject: Re: [PATCH] rcu-tasks: Warn on too-short RCU Tasks Rude grace period To: "Joel Fernandes" Cc: paulmck@kernel.org, frederic@kernel.org, neeraj.upadhyay@kernel.org, urezki@gmail.com, boqun@kernel.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <970F52C9-3198-4BD1-B1A9-6A4B24F550AA@nvidia.com> References: <20261015094619.8773-1-qiang.zhang@linux.dev> <970F52C9-3198-4BD1-B1A9-6A4B24F550AA@nvidia.com> >=20 >=20>=20 >=20> On Oct 15, 2026, at 5:46 AM, Zqiang wrote: > >=20=20 >=20> The RCU Tasks Rude grace period is implemented by invoking the > > schedule_on_each_cpu() with an empty work function, which forces > > a context switch on every online CPU and guarantees that all > > rude-tasks read-side critical sections have completed. However, > > schedule_on_each_cpu() can fail (via alloc_percpu() returning > > -ENOMEM) and returns immediately, in which case those context > > switches never happen, too-short grace period happen. > >=20=20 >=20> This commit therefore wraps the schedule_on_each_cpu() call in > > WARN_ONCE() so that this failure is reported as a "Too-short > > grace period" warning. > >=20=20 >=20> Signed-off-by: Zqiang > > --- > > kernel/rcu/tasks.h | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > >=20=20 >=20> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h > > index fcac7361ec51..91c25717402e 100644 > > --- a/kernel/rcu/tasks.h > > +++ b/kernel/rcu/tasks.h > > @@ -1361,7 +1361,8 @@ static void rcu_tasks_be_rude(struct work_stru= ct *work) > > static void rcu_tasks_rude_wait_gp(struct rcu_tasks *rtp) > > { > > rtp->n_ipis +=3D cpumask_weight(cpu_online_mask); > > - schedule_on_each_cpu(rcu_tasks_be_rude); > > + WARN_ONCE(schedule_on_each_cpu(rcu_tasks_be_rude), > > + "%s: Too-short grace period, OOM is now expected behavior!!!\n", r= tp->name); > >=20 >=20Is that the best error message? OOM is expected when grace periods do= not conclude. >=20 Hi,=20Joel I will resend v2, use DEFINE_PER_CPU() to replace alloc_percpu() to alloc= ate work_struct objects. Thanks Zqiang > Thanks. >=20 >=20>=20 >=20> } > >=20=20 >=20> static void call_rcu_tasks_rude(struct rcu_head *rhp, rcu_callback= _t func); > > -- > > 2.17.1 > > >