linux-kernel - Re: [PATCH 1/2] uio: change to use the mutex lock instead of the spin lock

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Message-ID: <20180705163338.GA14941@kroah.com>
Date:   Thu, 5 Jul 2018 18:33:38 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     xiubli@...hat.com
Cc:     linux-kernel@...r.kernel.org, pkalever@...hat.com,
        pkarampu@...hat.com, atumball@...hat.com, sabose@...hat.com,
        mchristi@...hat.com
Subject: Re: [PATCH 1/2] uio: change to use the mutex lock instead of the
 spin lock

On Thu, Jul 05, 2018 at 12:27:27PM -0400, xiubli@...hat.com wrote:
> From: Xiubo Li <xiubli@...hat.com>
> 
> We are hitting a regression with the following commit:
> 
> commit a93e7b331568227500186a465fee3c2cb5dffd1f
> Author: Hamish Martin <hamish.martin@...iedtelesis.co.nz>
> Date:   Mon May 14 13:32:23 2018 +1200
> 
>     uio: Prevent device destruction while fds are open
> 
> The problem is the addition of spin_lock_irqsave in uio_write. This
> leads to hitting  uio_write -> copy_from_user -> _copy_from_user ->
> might_fault and the logs filling up with sleeping warnings.
> 
> I also noticed some uio drivers allocate memory, sleep, grab mutexes
> from callouts like open() and release and uio is now doing
> spin_lock_irqsave while calling them.
> 
> Reported-by: Mike Christie <mchristi@...hat.com>
> Signed-off-by: Xiubo Li <xiubli@...hat.com>
> ---
>  drivers/uio/uio.c          | 33 ++++++++++++++-------------------
>  include/linux/uio_driver.h |  2 +-
>  2 files changed, 15 insertions(+), 20 deletions(-)

Any specific reason you did not also cc: the author of the above patch
to review this one?

Please fix up and resend.

greg k-h