From: Alan Stern <stern@rowland.harvard.edu>
To: Jim Baxter <jim_baxter@mentor.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-usb@vger.kernel.org,
"Resch Carsten \(CM/ESO6\)" <Carsten.Resch@de.bosch.com>,
"Rosca, Eugeniu \(ADITG/ESB\)" <erosca@de.adit-jv.com>
Subject: Re: PROBLEM: Long Workqueue delays.
Date: Mon, 17 Aug 2020 11:25:07 -0400 [thread overview]
Message-ID: <20200817152507.GC112820@rowland.harvard.edu> (raw)
In-Reply-To: <71aafe68-7fe0-6b77-ea8e-83edd3f16c8d@mentor.com>
On Mon, Aug 17, 2020 at 12:40:03PM +0100, Jim Baxter wrote:
> We have issues with the workqueue of the kernel overloading the CPU 0
> when we we disconnect a USB stick.
Do you unmount the stick before disconnecting it?
> This results in other items on the shared workqueue being delayed by
> around 6.5 seconds with a default kernel configuration and 2.3 seconds
> on a config tailored for our RCar embedded platform.
>
> I am aware there will be delays on the shared workqueue, are the delays
> we are seeing considered normal?
Assuming the workqueue delay is caused by the USB subsystem, you may be
able to get more information by turning on USB dynamic debugging:
echo 'module usbcore =p' >/sys/kernel/debug/dynamic_debug/control
and seeing what shows up in the dmesg log.
One long-running job should not normally be enough to delay an entire
workqueues. Workqueues are allowed to spawn multiple threads; they are
supposed to resize themselves dynamically as required.
Alan Stern
prev parent reply other threads:[~2020-08-17 15:25 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-17 11:40 Jim Baxter
2020-08-17 11:57 ` Greg KH
2020-08-17 18:24 ` Jim Baxter
2020-08-17 18:47 ` Alan Stern
2020-08-18 10:54 ` Jim Baxter
2020-08-18 14:48 ` Alan Stern
2020-08-17 15:25 ` Alan Stern [this message]
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