linux-kernel - Re: [PATCH 4.19 83/92] mfd: dln2: Run event handler loop under spinlock

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Date:   Fri, 21 Aug 2020 13:21:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Pavel Machek <pavel@...x.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Stable <stable@...r.kernel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 83/92] mfd: dln2: Run event handler loop under
 spinlock

On Fri, Aug 21, 2020 at 01:54:49PM +0300, Andy Shevchenko wrote:
> On Fri, Aug 21, 2020 at 11:15:10AM +0200, Greg Kroah-Hartman wrote:
> > On Fri, Aug 21, 2020 at 11:14:16AM +0200, Greg Kroah-Hartman wrote:
> > > On Fri, Aug 21, 2020 at 12:06:45PM +0300, Andy Shevchenko wrote:
> > > > On Fri, Aug 21, 2020 at 10:26 AM Pavel Machek <pavel@...x.de> wrote:
> > > > > > From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > > > > >
> > > > > > [ Upstream commit 3d858942250820b9adc35f963a257481d6d4c81d ]
> > > > > >
> > > > > > The event handler loop must be run with interrupts disabled.
> > > > > > Otherwise we will have a warning:
> > > > > ...
> > > > > > Recently xHCI driver switched to tasklets in the commit 36dc01657b49
> > > > > > ("usb: host: xhci: Support running urb giveback in tasklet
> > > > > > context").
> > > > >
> > > > > AFAICT, 36dc01657b49 is not included in 4.19.141, so this commit
> > > > > should not be needed, either.
> > > > 
> > > > I'm wondering if there are any other USB host controller drivers that
> > > > use URB giveback in interrupt enabled context.
> > > 
> > > Almost all do.
> > 
> > Sorry, read that the wrong way, most have interrupts disabled, so this
> > change should be fine.
> 
> The change is harmless in these cases. I was wondering if it actually *helps*
> in some cases besides xHCI.

It might, I forgot about usbip, which probably runs in this mode.

thanks,

greg k-h