From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH v2 4/5] blk-iocost: fix sleeping in atomic context warnning Date: Mon, 14 Nov 2022 12:07:45 -1000 Message-ID: References: <20221104023938.2346986-1-yukuai1@huaweicloud.com> <20221104023938.2346986-5-yukuai1@huaweicloud.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=MWARFSddCBGf3aDJ1ajp1vvhpqhBLlESZgXSjfkXOvE=; b=Rj3+QSD9G8LsBjjcl+TZ+GbTq/H+NRXDvqWs514daNHR6TDjwFkYDPf1p7/YOF7hO6 Tb+lHshVBcpxKv2DQ1iH59S8BS+QoFNTkf1gRW2LnSsr8EkGAL351/5lMZioGE7gAVT+ Uv9bbkWdcUahORFNMt6ilxcyZ+7jjA0wayeIGf9nKRcJjikKX7tI6XB2R/4AJhHWaumP Blb+W0FP+SPDMTFOyNx335xcG/5z/pQcPEBZ80MC0OyrPSAltOXYzi6RRjUOfGYqpwAN 5ZRxTO930TiFg4XjmFKFIujDHdHsJ4gFbylwG7bIzdOJvbwo4FXiC2D46TLjfpQTVEdl 1ogQ== Sender: Tejun Heo Content-Disposition: inline In-Reply-To: <20221104023938.2346986-5-yukuai1-XF6JlduFytWkHkcT6e4Xnw@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Yu Kuai Cc: hch-jcswGhMUV9g@public.gmane.org, josef-DigfWCa+lFGyeJad7bwFQA@public.gmane.org, axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, yukuai3-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, yi.zhang-hv44wF8Li93QT0dZR+AlfA@public.gmane.org On Fri, Nov 04, 2022 at 10:39:37AM +0800, Yu Kuai wrote: > From: Yu Kuai > > match_u64() is called inside ioc->lock, which causes smatch static > checker warnings: > > block/blk-iocost.c:3211 ioc_qos_write() warn: sleeping in atomic context > block/blk-iocost.c:3240 ioc_qos_write() warn: sleeping in atomic context > block/blk-iocost.c:3407 ioc_cost_model_write() warn: sleeping in atomic > context > > Fix the problem by introducing a mutex and using it while prasing input > params. It bothers me that parsing an u64 string requires a GFP_KERNEL memory allocation. > @@ -2801,9 +2806,11 @@ static void ioc_rqos_queue_depth_changed(struct rq_qos *rqos) > { > struct ioc *ioc = rqos_to_ioc(rqos); > > + mutex_lock(&ioc->params_mutex); > spin_lock_irq(&ioc->lock); > ioc_refresh_params(ioc, false); > spin_unlock_irq(&ioc->lock); > + mutex_unlock(&ioc->params_mutex); > } Aren't the params still protected by ioc->lock? Why do we need to grab both? Any chance I can persuade you into updating match_NUMBER() helpers to not use match_strdup()? They can easily disable irq/preemption and use percpu buffers and we won't need most of this patchset. Thanks. -- tejun