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Date:   Tue, 18 Aug 2020 10:48:18 -0400
From:   Alan Stern <stern@rowland.harvard.edu>
To:     Jim Baxter <jim_baxter@mentor.com>
Cc:     Greg KH <gregkh@linuxfoundation.org>, 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.
Message-ID: <20200818144818.GB144306@rowland.harvard.edu>
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On Tue, Aug 18, 2020 at 11:54:51AM +0100, Jim Baxter wrote:
> On 17/08/2020 19:47, Alan Stern wrote:
> > 
> > Unplugging a R/W USB drive without unmounting it first is a great way to 
> > corrupt the data.
> > 
> Thank you, post development we will only mount the USB stick as R/O.
> 
> >> Using perf Iidentified the hub_events workqueue was spending a lot of time in
> >> invalidate_partition(), I have included a cut down the captured data from perf in
> >> [2] which shows the additional functions where the kworker spends most of its time.
> > 
> > invalidate_partition() is part of the block layer, not part of USB.  It 
> > gets called whenever a drive is removed from the system, no matter what 
> > type of drive it is.  You should ask the people involved in that 
> > subsystem why it takes so long.
> > 
> 
> I included the linux-mm list but missed the filesystem, I will ask the question
> to the linux-fsdevel too.

What about linux-block?  The block layer is different from the 
memory-management (mm) layer.

Alan Stern