Re: [PATCH v5 10/24] tick/nohz: Move tick_nohz_full_mask declaration outside the #ifdef

From: Reinette Chatre <reinette.chatre@intel.com>
To: James Morse <james.morse@arm.com>, <x86@kernel.org>,
	<linux-kernel@vger.kernel.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	H Peter Anvin <hpa@zytor.com>, Babu Moger <Babu.Moger@amd.com>,
	<shameerali.kolothum.thodi@huawei.com>,
	D Scott Phillips OS <scott@os.amperecomputing.com>,
	<carl@os.amperecomputing.com>, <lcherian@marvell.com>,
	<bobo.shaobowang@huawei.com>, <tan.shaopeng@fujitsu.com>,
	<xingxin.hx@openanolis.org>, <baolin.wang@linux.alibaba.com>,
	Jamie Iles <quic_jiles@quicinc.com>,
	Xin Hao <xhao@linux.alibaba.com>, <peternewman@google.com>,
	<dfustini@baylibre.com>
Subject: Re: [PATCH v5 10/24] tick/nohz: Move tick_nohz_full_mask declaration outside the #ifdef
Date: Wed, 9 Aug 2023 15:34:09 -0700	[thread overview]
Message-ID: <989616c3-ea4c-1c9b-b857-6d8bcb4843bd@intel.com> (raw)
In-Reply-To: <20230728164254.27562-11-james.morse@arm.com>

Hi James,

On 7/28/2023 9:42 AM, James Morse wrote:
> tick_nohz_full_mask lists the CPUs that are nohz_full. This is only
> needed when CONFIG_NO_HZ_FULL is defined. tick_nohz_full_cpu() allows
> a specific CPU to be tested against the mask, and evaluates to false
> when CONFIG_NO_HZ_FULL is not defined.
> 
> The resctrl code needs to pick a CPU to run some work on, a new helper
> prefers housekeeping CPUs by examining the tick_nohz_full_mask. Hiding
> the declaration behind #ifdef CONFIG_NO_HZ_FULL forces all the users to
> be behind an ifdef too.
> 
> Move the tick_nohz_full_mask declaration, this lets callers drop the
> ifdef, and guard access to tick_nohz_full_mask with IS_ENABLED() or
> something like tick_nohz_full_cpu().
> 
> The definition does not need to be moved as any callers should be
> removed at compile time unless CONFIG_NO_HZ_FULL is defined.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
>  include/linux/tick.h | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)

This is outside of the resctrl area. What is the upstreaming
plan for this patch?

Reinette