[PATCH 09/33] block: Protect against concurrent isolated cpuset change

[Jens Axboe]

On 12/24/25 6:44 AM, Frederic Weisbecker wrote:
> The block subsystem prevents running the workqueue to isolated CPUs,
> including those defined by cpuset isolated partitions. Since
> HK_TYPE_DOMAIN will soon contain both and be subject to runtime
> modifications, synchronize against housekeeping using the relevant lock.
> 
> For full support of cpuset changes, the block subsystem may need to
> propagate changes to isolated cpumask through the workqueue in the
> future.
> 
> Signed-off-by: Frederic Weisbecker <frederic at kernel.org>
> ---
>  block/blk-mq.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 1978eef95dca..0037af1216f3 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -4257,12 +4257,16 @@ static void blk_mq_map_swqueue(struct request_queue *q)
>  
>  		/*
>  		 * Rule out isolated CPUs from hctx->cpumask to avoid
> -		 * running block kworker on isolated CPUs
> +		 * running block kworker on isolated CPUs.
> +		 * FIXME: cpuset should propagate further changes to isolated CPUs
> +		 * here.
>  		 */
> +		rcu_read_lock();
>  		for_each_cpu(cpu, hctx->cpumask) {
>  			if (cpu_is_isolated(cpu))
>  				cpumask_clear_cpu(cpu, hctx->cpumask);
>  		}
> +		rcu_read_unlock();

Want me to just take this one separately and get it out of your hair?
Doesn't seem to have any dependencies.

-- 
Jens Axboe