From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout.efficios.com (smtpout.efficios.com [167.114.26.122]) (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 B24ED12AAC8; Mon, 29 Apr 2024 17:51:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=167.114.26.122 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714413092; cv=none; b=clvlNZ5ZYcHYsySRr0RvV8wy7CtXxl2qGnwnaabJhaP2yl/HCCWseSqvQruYgULdU7J/vXHpj2IQNhvhcso4SkKIQmFpnLBHiaqZgaigDkozvlGyJpaQVXN9rpXK60FUHbliT4+dktEwoW52a8Z2cM3bmH6S6rfwcDBJme5re7U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714413092; c=relaxed/simple; bh=t19PgdJpK6QrPLPRYG83UaeAXKiRFqADD1jgilmOirc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=dPKMPyG3GDkuvRCHH0r12OORooDCrWqfd/3UBrVU1fhilKVgfwO8TriZZGsm31dDsWxiKCfZnNQUTjoy/o52iOzMWrqm8ij/u/7y+aM683p5mB6ZPxAodhJ3ImIZ4aW4SzIPjnS0RgMemeodksWmz97/ZVhovVuME2xqOPCFIWk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com; spf=pass smtp.mailfrom=efficios.com; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b=paTPmGLj; arc=none smtp.client-ip=167.114.26.122 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=efficios.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="paTPmGLj" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1714412575; bh=t19PgdJpK6QrPLPRYG83UaeAXKiRFqADD1jgilmOirc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=paTPmGLjUVBSJVvGRn8VWTzBxVO2DJr2CsBGm24/SdSCKJdlnNxCE4mf3xkvqRx7u Oo5RY0ApG0ND7BBzzXYMQrZWB31Jdi8vedw1q1XP5QAzjAvO1Hya6B/8mrM2UPnYMU kNrMeYX77Px1UnphTDPy/BCJi1W5HZ36sPLrqyeEPSDPGKT8RqWEb3sSrYEsreS1KK ljsSDQmmvYGlOjRxY3KoOKj7noix9f/JmVEcXJ1oI82RLp3+LInCNAco5kVSpNzOOR YjfJk1/u9lagoB72wyEcZO1x8mBAQesHnSb6mMBfBXvnaWqx/U6oWt7n/vwzIpVRQz Bo1SyEyP/LeAA== Received: from [172.16.0.134] (192-222-143-198.qc.cable.ebox.net [192.222.143.198]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4VSrJb0wQXzxfT; Mon, 29 Apr 2024 13:42:55 -0400 (EDT) Message-ID: Date: Mon, 29 Apr 2024 13:43:10 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] rcu: Remove unreachable logic To: Alan Huang , paulmck@kernel.org, frederic@kernel.org, neeraj.upadhyay@kernel.org, joel@joelfernandes.org, josh@joshtriplett.org, boqun.feng@gmail.com, rostedt@goodmis.org, jiangshanlai@gmail.com, qiang.zhang1211@gmail.com Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240429173439.1685274-1-mmpgouride@gmail.com> Content-Language: en-US From: Mathieu Desnoyers In-Reply-To: <20240429173439.1685274-1-mmpgouride@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2024-04-29 13:34, Alan Huang wrote: > call_rcu_core is only called from __call_rcu_common with interrupt > disabled. This patch thus removes the unreachable logic and the would-be > unused 'flags' parameter. Nack. call_rcu_core() receives a @flags parameter which are the _saved_ flags as they were prior to local_irq_save(). This patch highlights a misunderstanding of what the code is actually doing. Thanks, Mathieu > > Signed-off-by: Alan Huang > --- > kernel/rcu/tree.c | 35 ++--------------------------------- > 1 file changed, 2 insertions(+), 33 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index d5507ac1bbf1..b0ea2ebd7769 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -2983,7 +2983,7 @@ static void rcutree_enqueue(struct rcu_data *rdp, struct rcu_head *head, rcu_cal > * Handle any core-RCU processing required by a call_rcu() invocation. > */ > static void call_rcu_core(struct rcu_data *rdp, struct rcu_head *head, > - rcu_callback_t func, unsigned long flags) > + rcu_callback_t func) > { > rcutree_enqueue(rdp, head, func); > /* > @@ -2992,37 +2992,6 @@ static void call_rcu_core(struct rcu_data *rdp, struct rcu_head *head, > */ > if (!rcu_is_watching()) > invoke_rcu_core(); > - > - /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ > - if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) > - return; > - > - /* > - * Force the grace period if too many callbacks or too long waiting. > - * Enforce hysteresis, and don't invoke rcu_force_quiescent_state() > - * if some other CPU has recently done so. Also, don't bother > - * invoking rcu_force_quiescent_state() if the newly enqueued callback > - * is the only one waiting for a grace period to complete. > - */ > - if (unlikely(rcu_segcblist_n_cbs(&rdp->cblist) > > - rdp->qlen_last_fqs_check + qhimark)) { > - > - /* Are we ignoring a completed grace period? */ > - note_gp_changes(rdp); > - > - /* Start a new grace period if one not already started. */ > - if (!rcu_gp_in_progress()) { > - rcu_accelerate_cbs_unlocked(rdp->mynode, rdp); > - } else { > - /* Give the grace period a kick. */ > - rdp->blimit = DEFAULT_MAX_RCU_BLIMIT; > - if (READ_ONCE(rcu_state.n_force_qs) == rdp->n_force_qs_snap && > - rcu_segcblist_first_pend_cb(&rdp->cblist) != head) > - rcu_force_quiescent_state(); > - rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs); > - rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); > - } > - } > } > > /* > @@ -3121,7 +3090,7 @@ __call_rcu_common(struct rcu_head *head, rcu_callback_t func, bool lazy_in) > if (unlikely(rcu_rdp_is_offloaded(rdp))) > call_rcu_nocb(rdp, head, func, flags, lazy); > else > - call_rcu_core(rdp, head, func, flags); > + call_rcu_core(rdp, head, func); > local_irq_restore(flags); > } > -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com