Re: [PATCH v2] mt76: fix schedule while atomic in mt76x02_reset_state

[Stanislaw Gruszka <sgruszka@redhat.com>]

On Wed, Mar 13, 2019 at 10:36:39AM +0100, Lorenzo Bianconi wrote:
> >
> > On Wed, Mar 13, 2019 at 10:31:11AM +0100, Lorenzo Bianconi wrote:
> > > >
> > > > On Tue, Mar 12, 2019 at 05:48:14PM +0100, Lorenzo Bianconi wrote:
> > > > > >
> > > > > > On Mon, Mar 11, 2019 at 02:24:35PM +0100, Lorenzo Bianconi wrote:
> > > > > > > Fix following schedule while atomic in mt76x02_reset_state
> > > > > > > since synchronize_rcu is run inside a RCU section
> > > > > > >
> > > > > > > [44036.944222] mt76x2e 0000:06:00.0: MCU message 31 (seq 3) timed out
> > > > > > > [44036.944281] BUG: sleeping function called from invalid context at kernel/rcu/tree_exp.h:818
> > > > > > > [44036.944284] in_atomic(): 1, irqs_disabled(): 0, pid: 28066, name: kworker/u4:1
> > > > > > > [44036.944287] INFO: lockdep is turned off.
> > > > > > > [44036.944292] CPU: 1 PID: 28066 Comm: kworker/u4:1 Tainted: G        W         5.0.0-rc7-wdn-t1+ #7
> > > > > > > [44036.944294] Hardware name: Dell Inc. Studio XPS 1340/0K183D, BIOS A11 09/08/2009
> > > > > > > [44036.944305] Workqueue: phy1 mt76x02_wdt_work [mt76x02_lib]
> > > > > > > [44036.944308] Call Trace:
> > > > > > > [44036.944317]  dump_stack+0x67/0x90
> > > > > > > [44036.944322]  ___might_sleep.cold.88+0x9f/0xaf
> > > > > > > [44036.944327]  rcu_blocking_is_gp+0x13/0x50
> > > > > > > [44036.944330]  synchronize_rcu+0x17/0x80
> > > > > > > [44036.944337]  mt76_sta_state+0x138/0x1d0 [mt76]
> > > > > > > [44036.944349]  mt76x02_wdt_work+0x1c9/0x610 [mt76x02_lib]
> > > > > > > [44036.944355]  process_one_work+0x2a5/0x620
> > > > > > > [44036.944361]  worker_thread+0x35/0x3e0
> > > > > > > [44036.944368]  kthread+0x11c/0x140
> > > > > > > [44036.944376]  ret_from_fork+0x3a/0x50
> > > > > > > [44036.944384] BUG: scheduling while atomic: kworker/u4:1/28066/0x00000002
> > > > > > > [44036.944387] INFO: lockdep is turned off.
> > > > > > > [44036.944389] Modules linked in: cmac ctr ccm af_packet snd_hda_codec_hdmi
> > > > > >
> > > > > > Does the patch fix the issue for you ? For me on my MT7612E device it
> > > > > > make the BUG warning gone, but instead of that I have total system hung
> > > > > > without any error message except information about hw restart.
> > >
> > > The system hang is not related to the 'schedule while atomic'.
> > > If you look at the code we run synchronize_rcu() inside a rcu section
> > > and this is not allowed.
> > > I just run it outside of the rcu section protecting it with the mutex,
> > > the reset is performed even with
> > > this patch (just look at syslog). The system hang is related to this
> > > particular card since other devices
> > > work properly.
> >
> > Ok, so it works for you. That I wanted to know.
> 
> If you mean:
> - the reset is performed: yes

I meant the reset works on mt76x2e without hung on SMP machines
(on whatever card).

Stanislaw