linux-kernel - Re: [PATCH v2] scsi: Introduce sdev_printk_ratelimited to throttle frequent printk

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Date:   Mon, 2 Apr 2018 10:37:35 +0800
From:   Jason Yan <yanaijie@...wei.com>
To:     Wen Yang <wen.yang99@....com.cn>, <jejb@...ux.vnet.ibm.com>,
        <martin.petersen@...cle.com>
CC:     <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <Bart.VanAssche@....com>, <pmladek@...e.com>,
        <sergey.senozhatsky.work@...il.com>, <tj@...nel.org>,
        <jiang.biao2@....com.cn>, <zhong.weidong@....com.cn>,
        Tan Hu <tan.hu@....com.cn>
Subject: Re: [PATCH v2] scsi: Introduce sdev_printk_ratelimited to throttle
 frequent printk

Hi, Yang,

On 2018/4/2 9:58, Wen Yang wrote:
> There would be so many same lines printed by frequent printk if one
> disk went wrong, like,
> [  546.185242] sd 0:1:0:0: rejecting I/O to offline device
> [  546.185258] sd 0:1:0:0: rejecting I/O to offline device
> [  546.185280] sd 0:1:0:0: rejecting I/O to offline device
> [  546.185307] sd 0:1:0:0: rejecting I/O to offline device
> [  546.185334] sd 0:1:0:0: rejecting I/O to offline device
> [  546.185364] sd 0:1:0:0: rejecting I/O to offline device
> [  546.185390] sd 0:1:0:0: rejecting I/O to offline device
> [  546.185410] sd 0:1:0:0: rejecting I/O to offline device
> For slow serial console, the frequent printk may be blocked for a
> long time, and if any spin_lock has been acquired before the printk
> like in scsi_request_fn, watchdog could be triggered.
>
> Related disscussion can be found here,
> https://bugzilla.kernel.org/show_bug.cgi?id=199003
> And Petr brought the idea to throttle the frequent printk, it's
> useless to print the same lines frequently after all.
>

It's true that this print for the same device is useless. But it's
useful for different devices. Is it possible to limit the print only
for the same device?

Thanks,

Jason

>
>