Re: [PATCH v7 00/11] Stop monitoring disabled devices

Zhang Rui
2020-07-03T01:49:32Z

On Thu, 2020-07-02 at 19:49 +0200, Daniel Lezcano wrote:
> On 02/07/2020 19:19, Andrzej Pietrasiewicz wrote:
> > Hi,
> >
> > W dniu 02.07.2020 o 19:01, Daniel Lezcano pisze:
> > > On 02/07/2020 15:53, Andrzej Pietrasiewicz wrote:
> > > > Hi Daniel,
> > > >
> > > > <snip>
> > > >
> > > > > > > > >
> > > > > > > > > I did reproduce:
> > > > > > > > >
> > > > > > > > > v5.8-rc3 + series => imx6 hang at boot time
> > > > > > > > > v5.8-rc3 => imx6 boots correctly
> > > > >
> > > > > So finally I succeeded to reproduce it on my imx7 locally.
> > > > > The sensor
> > > > > was failing to initialize for another reason related to the
> > > > > legacy
> > > > > cooling device, this is why it is not appearing on the imx7.
> > > > >
> > > > > I can now git-bisect :)
> > > > >
> > > >
> > > > That would be very kind of you, thank you!
> > >
> > > With the lock correctness option enabled:
> > >
> > > [ 4.179223] imx_thermal tempmon: Extended Commercial CPU
> > > temperature
> > > grade - max:105C critical:100C passive:95C
> > > [ 4.189557]
> > > [ 4.191060] ============================================
> > > [ 4.196378] WARNING: possible recursive locking detected
> > > [ 4.201699] 5.8.0-rc3-00011-gf5e50bf4d3ef #42 Not tainted
> > > [ 4.207102] --------------------------------------------
> > > [ 4.212421] kworker/0:3/54 is trying to acquire lock:
> > > [ 4.217480] ca09a3e4 (&tz->lock){+.+.}-{3:3}, at:
> > > thermal_zone_device_is_enabled+0x18/0x34
> > > [ 4.225777]
> > > [ 4.225777] but task is already holding lock:
> > > [ 4.231615] ca09a3e4 (&tz->lock){+.+.}-{3:3}, at:
> > > thermal_zone_get_temp+0x38/0x6c
> > > [ 4.239121]
> > > [ 4.239121] other info that might help us debug this:
> > > [ 4.245655] Possible unsafe locking scenario:
> > > [ 4.245655]
> > > [ 4.251579] CPU0
> > > [ 4.254031] ----
> > > [ 4.256481] lock(&tz->lock);
> > > [ 4.259544] lock(&tz->lock);
> > > [ 4.262608]
> > > [ 4.262608] *** DEADLOCK ***
> > > [ 4.262608]
> > > [ 4.268533] May be due to missing lock nesting notation
> > > [ 4.268533]
> > > [ 4.275329] 4 locks held by kworker/0:3/54:
> > > [ 4.279517] #0: cb0066a8 ((wq_completion)events){+.+.}-{0:0},
> > > at:
> > > process_one_work+0x224/0x808
> > > [ 4.288241] #1: ca075f10 (deferred_probe_work){+.+.}-{0:0},
> > > at:
> > > process_one_work+0x224/0x808
> > > [ 4.296787] #2: cb1a48d8 (&dev->mutex){....}-{3:3}, at:
> > > __device_attach+0x30/0x140
> > > [ 4.304468] #3: ca09a3e4 (&tz->lock){+.+.}-{3:3}, at:
> > > thermal_zone_get_temp+0x38/0x6c
> > > [ 4.312408]
> > > [ 4.312408] stack backtrace:
> > > [ 4.316778] CPU: 0 PID: 54 Comm: kworker/0:3 Not tainted
> > > 5.8.0-rc3-00011-gf5e50bf4d3ef #42
> > > [ 4.325048] Hardware name: Freescale i.MX7 Dual (Device Tree)
> > > [ 4.330809] Workqueue: events deferred_probe_work_func
> > > [ 4.335973] [<c0312384>] (unwind_backtrace) from [<c030c580>]
> > > (show_stack+0x10/0x14)
> > > [ 4.343734] [<c030c580>] (show_stack) from [<c079d7d8>]
> > > (dump_stack+0xe8/0x114)
> > > [ 4.351062] [<c079d7d8>] (dump_stack) from [<c03abf78>]
> > > (__lock_acquire+0xbfc/0x2cb4)
> > > [ 4.358909] [<c03abf78>] (__lock_acquire) from [<c03ae9c4>]
> > > (lock_acquire+0xf4/0x4e4)
> > > [ 4.366758] [<c03ae9c4>] (lock_acquire) from [<c10630fc>]
> > > (__mutex_lock+0xb0/0xaa8)
> > > [ 4.374431] [<c10630fc>] (__mutex_lock) from [<c1063b10>]
> > > (mutex_lock_nested+0x1c/0x24)
> > > [ 4.382452] [<c1063b10>] (mutex_lock_nested) from [<c0d932c0>]
> > > (thermal_zone_device_is_enabled+0x18/0x34)
> > > [ 4.392036] [<c0d932c0>] (thermal_zone_device_is_enabled) from
> > > [<c0d9da90>] (imx_get_temp+0x30/0x208)
> > > [ 4.401271] [<c0d9da90>] (imx_get_temp) from [<c0d97484>]
> > > (thermal_zone_get_temp+0x4c/0x6c)
> > > [ 4.409640] [<c0d97484>] (thermal_zone_get_temp) from
> > > [<c0d93df0>]
> > > (thermal_zone_device_update+0x8c/0x258)
> > > [ 4.419310] [<c0d93df0>] (thermal_zone_device_update) from
> > > [<c0d9401c>] (thermal_zone_device_set_mode+0x60/0x88)
> > > [ 4.429500] [<c0d9401c>] (thermal_zone_device_set_mode) from
> > > [<c0d9e1d4>] (imx_thermal_probe+0x3e4/0x578)
> > > [ 4.439082] [<c0d9e1d4>] (imx_thermal_probe) from [<c0a78388>]
> > > (platform_drv_probe+0x48/0x98)
> > > [ 4.447622] [<c0a78388>] (platform_drv_probe) from
> > > [<c0a7603c>]
> > > (really_probe+0x218/0x348)
> > > [ 4.455903] [<c0a7603c>] (really_probe) from [<c0a76278>]
> > > (driver_probe_device+0x5c/0xb4)
> > > [ 4.464098] [<c0a76278>] (driver_probe_device) from
> > > [<c0a743bc>]
> > > (bus_for_each_drv+0x58/0xb8)
> > > [ 4.472638] [<c0a743bc>] (bus_for_each_drv) from [<c0a75db0>]
> > > (__device_attach+0xd4/0x140)
> > > [ 4.480919] [<c0a75db0>] (__device_attach) from [<c0a750b0>]
> > > (bus_probe_device+0x88/0x90)
> > > [ 4.489112] [<c0a750b0>] (bus_probe_device) from [<c0a75564>]
> > > (deferred_probe_work_func+0x68/0x98)
> > > [ 4.498088] [<c0a75564>] (deferred_probe_work_func) from
> > > [<c0369988>]
> > > (process_one_work+0x2e0/0x808)
> > > [ 4.507237] [<c0369988>] (process_one_work) from [<c036a150>]
> > > (worker_thread+0x2a0/0x59c)
> > > [ 4.515432] [<c036a150>] (worker_thread) from [<c0372208>]
> > > (kthread+0x16c/0x178)
> > > [ 4.522843] [<c0372208>] (kthread) from [<c0300174>]
> > > (ret_from_fork+0x14/0x20)
> > > [ 4.530074] Exception stack(0xca075fb0 to 0xca075ff8)
> > > [ 4.535138] 5fa0: 00000000
> > > 00000000 00000000 00000000
> > > [ 4.543328] 5fc0: 00000000 00000000 00000000 00000000 00000000
> > > 00000000 00000000 00000000
> > > [ 4.551516] 5fe0: 00000000 00000000 00000000 00000000 00000013
> > > 00000000
> > >
> > >
> > >
> >
> > Thanks!
> >
> > That confirms your suspicions.
> >
> > So the reason is that ->get_temp() is called while the mutex is
> > held and
> > thermal_zone_device_is_enabled() wants to take the same mutex.
>
> Yes, that's correct.
>
> > Is adding a comment to thermal_zone_device_is_enabled() to never
> > call
> > it while the mutex is held and adding another version of it which
> > does
> > not take the mutex ok?
>
> The thermal_zone_device_is_enabled() is only used in two places, acpi
> and this imx driver, and given:
>
> 1. as soon as the mutex is released, there is no guarantee the
> thermal
> zone won't be changed right after, the lock is pointless, thus the
> information also.
>
> 2. from a design point of view, I don't see why a driver should know
> if
> a thermal zone is disabled or not
>
> It would make sense to end with this function and do not give the
> different drivers an opportunity to access this information.

I agree.
>
> Why not add change_mode for the acpi in order to enable or disable
> the
> events

thermal_zone_device_is_enabled() is invoked in acpi thermal driver
because we only want to do thermal_zone_device_update() when the acpi
thermal zone is enabled.

As thermal_zone_device_update() can handle a disabled thermal zone now,
we can just remove the check.

thanks,
rui

> and for imx_thermal use irq_enabled flag instead of the thermal
> zone mode? Moreover it is very unclear why this function is needed in
> imx_get_temp(), and I suspect we should be able to get rid of it.
>
>