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From:   Saravana Kannan <saravanak@google.com>
Date:   Fri, 17 Jul 2020 10:31:13 -0700
Message-ID: <CAGETcx9quqtV9TeD8WEcLLijGeV+7hXqnyiMv7F8xo+vyF_7iw@mail.gmail.com>
Subject: Re: [PATCH v2] driver core: Fix sleeping in invalid context during
 device link deletion
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     Marek Szyprowski <m.szyprowski@samsung.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Android Kernel Team <kernel-team@android.com>,
        LKML <linux-kernel@vger.kernel.org>
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On Fri, Jul 17, 2020 at 9:34 AM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Fri, Jul 17, 2020 at 12:13:04AM +0200, Marek Szyprowski wrote:
> > Hi Saravana,
> >
> > On 16.07.2020 23:45, Saravana Kannan wrote:
> > > Marek and Guenter reported that commit 287905e68dd2 ("driver core:
> > > Expose device link details in sysfs") caused sleeping/scheduling while
> > > atomic warnings.
> > >
> > > BUG: sleeping function called from invalid context at kernel/locking/mutex.c:935
> > > in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 12, name: kworker/0:1
> > > 2 locks held by kworker/0:1/12:
> > >    #0: ee8074a8 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x174/0x7dc
> > >    #1: ee921f20 ((work_completion)(&sdp->work)){+.+.}-{0:0}, at: process_one_work+0x174/0x7dc
> > > Preemption disabled at:
> > > [<c01b10f0>] srcu_invoke_callbacks+0xc0/0x154
> > > ----- 8< ----- SNIP
> > > [<c064590c>] (device_del) from [<c0645c9c>] (device_unregister+0x24/0x64)
> > > [<c0645c9c>] (device_unregister) from [<c01b10fc>] (srcu_invoke_callbacks+0xcc/0x154)
> > > [<c01b10fc>] (srcu_invoke_callbacks) from [<c01493c4>] (process_one_work+0x234/0x7dc)
> > > [<c01493c4>] (process_one_work) from [<c01499b0>] (worker_thread+0x44/0x51c)
> > > [<c01499b0>] (worker_thread) from [<c0150bf4>] (kthread+0x158/0x1a0)
> > > [<c0150bf4>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
> > > Exception stack(0xee921fb0 to 0xee921ff8)
> > >
> > > This was caused by the device link device being released in the context
> > > of srcu_invoke_callbacks().  There is no need to wait till the RCU
> > > callback to release the device link device.  So release the device
> > > earlier and move the call_srcu() into the device release code. That way,
> > > the memory will get freed only after the device is released AND the RCU
> > > callback is called.
> > >
> > > Fixes: 287905e68dd2 ("driver core: Expose device link details in sysfs")
> > > Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > > Reported-by: Guenter Roeck <linux@roeck-us.net>
> > > Signed-off-by: Saravana Kannan <saravanak@google.com>
> > > ---
> > >
> > > v1->v2:
> > > - Better fix
> > > - Changed subject
> > > - v1 is this patch https://lore.kernel.org/lkml/20200716050846.2047110-1-saravanak@google.com/
> > >
> > > Marek and Guenter,
> > >
> > > I reproduced the original issue and tested this fix. Seems to work for
> > > me. Can you confirm?
> >
> > Confirmed, this one fixes the issue! :)
> >
> Same here.
>
> Tested-by: Guenter Roeck <linux@roeck-us.net>
>
> Guenter
>
> > Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> >

Thanks both.

Greg, can you review this and pull this into driver-core-next too?

-Saravana