Re: [PATCH v2 4/5] blk-iocost: fix sleeping in atomic context warnning
From: Tejun Heo <tj@kernel.org>
Date: 2022-11-14 22:07:52
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On Fri, Nov 04, 2022 at 10:39:37AM +0800, Yu Kuai wrote:
From: Yu Kuai <redacted> 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.
quoted hunk ↗ jump to hunk
@@ -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