Messages in this thread | | | Subject | Re: [PATCH v2 4/5] blk-iocost: fix sleeping in atomic context warnning | From | Yu Kuai <> | Date | Tue, 15 Nov 2022 09:16:52 +0800 |
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Hi,
在 2022/11/15 6:07, Tejun Heo 写道: > On Fri, Nov 04, 2022 at 10:39:37AM +0800, Yu Kuai wrote: >> From: Yu Kuai <yukuai3@huawei.com> >> >> 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?
Yes, the params is updated inside ioc->lock, but they can be read without the lock before updating them, which is protected by mutex instead.
> > 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.
Do you mean preallocated percpu buffer? Is there any example I can learn? Anyway, replace match_strdup() to avoid memory allocation sounds good.
Thanks, Kuai > > Thanks. >
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