linux-kernel - Re: [PATCH v8 10/12] blk-mq: use hk cpus only when isolcpus=io

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Message-ID: <4d006f81-cd3f-4aba-89db-fbc2e8c667b1@flourine.local>
Date: Mon, 8 Sep 2025 15:05:54 +0200
From: Daniel Wagner <dwagner@...e.de>
To: linux-nvme@...ts.infradead.org
Cc: Jens Axboe <axboe@...nel.dk>, Keith Busch <kbusch@...nel.org>, 
	Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>, 
	"Michael S. Tsirkin" <mst@...hat.com>, Aaron Tomlin <atomlin@...mlin.com>, 
	"Martin K. Petersen" <martin.petersen@...cle.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Costa Shulyupin <costa.shul@...hat.com>, Juri Lelli <juri.lelli@...hat.com>, 
	Valentin Schneider <vschneid@...hat.com>, Waiman Long <llong@...hat.com>, Ming Lei <ming.lei@...hat.com>, 
	Frederic Weisbecker <frederic@...nel.org>, Mel Gorman <mgorman@...e.de>, Hannes Reinecke <hare@...e.de>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, linux-kernel@...r.kernel.org, linux-block@...r.kernel.org, 
	megaraidlinux.pdl@...adcom.com, linux-scsi@...r.kernel.org, storagedev@...rochip.com, 
	virtualization@...ts.linux.dev, GR-QLogic-Storage-Upstream@...vell.com
Subject: Re: [PATCH v8 10/12] blk-mq: use hk cpus only when isolcpus=io_queue
 is enabled

On Mon, Sep 08, 2025 at 09:36:35AM +0200, Daniel Wagner wrote:
> which resulted in a way cleaner code. Though the kernel test robot
> complained with
> 
>       >> block/blk-mq-cpumap.c:155:16: error: array initializer must be an initializer list
>            155 |         cpumask_var_t active_hctx __free(free_cpumask_var) = NULL;
> 
> I try to figure out if it's possible to get this somehow working with
> some witchcraft (aka pre compiler magic).

What about adding something like this here:


#ifdef CONFIG_CPUMASK_OFFSTACK

#define scoped_cpumask_var(_name)			\
	cpumask_var_t _name __free(free_cpumask_var) = NULL;

#else /* ! CONFIG_CPUMASK_OFFSTACK */

#define scoped_cpumask_var(_name)			\
	cpumask_var_t _name __free(free_cpumask_var);

#endif /* ! CONFIG_CPUMASK_OFFSTACK */


This would make the new code way cleaner.