Re: [PATCH] leds: trigger: fix potential deadlock with libata

From: Boqun Feng
Date: Wed Nov 25 2020 - 09:02:29 EST

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On Wed, Nov 25, 2020 at 01:46:48PM +0100, Pavel Machek wrote:
> Hi!
>
> > We have the following potential deadlock condition:
> >
> > ========================================================
> > WARNING: possible irq lock inversion dependency detected
> > 5.10.0-rc2+ #25 Not tainted
> > --------------------------------------------------------
> > swapper/3/0 just changed the state of lock:
> > ffff8880063bd618 (&host->lock){-...}-{2:2}, at: ata_bmdma_interrupt+0x27/0x200
> > but this lock took another, HARDIRQ-READ-unsafe lock in the past:
> > (&trig->leddev_list_lock){.+.?}-{2:2}
> >
> > and interrupts could create inverse lock ordering between them.
> >
> > other info that might help us debug this:
> > Possible interrupt unsafe locking scenario:
> >
> > CPU0 CPU1
> > ---- ----
> > lock(&trig->leddev_list_lock);
> > local_irq_disable();
> > lock(&host->lock);
> > lock(&trig->leddev_list_lock);
> > <Interrupt>
> > lock(&host->lock);
> >
> > *** DEADLOCK ***
> >
> > no locks held by swapper/3/0.
> >
> > the shortest dependencies between 2nd lock and 1st lock:
> > -> (&trig->leddev_list_lock){.+.?}-{2:2} ops: 46 {
> > HARDIRQ-ON-R at:
> > lock_acquire+0x15f/0x420
> > _raw_read_lock+0x42/0x90
> > led_trigger_event+0x2b/0x70
> > rfkill_global_led_trigger_worker+0x94/0xb0
> > process_one_work+0x240/0x560
> > worker_thread+0x58/0x3d0
> > kthread+0x151/0x170
> > ret_from_fork+0x1f/0x30
> > IN-SOFTIRQ-R at:
> > lock_acquire+0x15f/0x420
> > _raw_read_lock+0x42/0x90
> > led_trigger_event+0x2b/0x70
> > kbd_bh+0x9e/0xc0
> > tasklet_action_common.constprop.0+0xe9/0x100
> > tasklet_action+0x22/0x30
> > __do_softirq+0xcc/0x46d
> > run_ksoftirqd+0x3f/0x70
> > smpboot_thread_fn+0x116/0x1f0
> > kthread+0x151/0x170
> > ret_from_fork+0x1f/0x30
> > SOFTIRQ-ON-R at:
> > lock_acquire+0x15f/0x420
> > _raw_read_lock+0x42/0x90
> > led_trigger_event+0x2b/0x70
> > rfkill_global_led_trigger_worker+0x94/0xb0
> > process_one_work+0x240/0x560
> > worker_thread+0x58/0x3d0
> > kthread+0x151/0x170
> > ret_from_fork+0x1f/0x30
> > INITIAL READ USE at:
> > lock_acquire+0x15f/0x420
> > _raw_read_lock+0x42/0x90
> > led_trigger_event+0x2b/0x70
> > rfkill_global_led_trigger_worker+0x94/0xb0
> > process_one_work+0x240/0x560
> > worker_thread+0x58/0x3d0
> > kthread+0x151/0x170
> > ret_from_fork+0x1f/0x30
> > }
> > ... key at: [<ffffffff83da4c00>] __key.0+0x0/0x10
> > ... acquired at:
> > _raw_read_lock+0x42/0x90
> > led_trigger_blink_oneshot+0x3b/0x90
> > ledtrig_disk_activity+0x3c/0xa0
> > ata_qc_complete+0x26/0x450
> > ata_do_link_abort+0xa3/0xe0
> > ata_port_freeze+0x2e/0x40
> > ata_hsm_qc_complete+0x94/0xa0
> > ata_sff_hsm_move+0x177/0x7a0
> > ata_sff_pio_task+0xc7/0x1b0
> > process_one_work+0x240/0x560
> > worker_thread+0x58/0x3d0
> > kthread+0x151/0x170
> > ret_from_fork+0x1f/0x30
> >
> > -> (&host->lock){-...}-{2:2} ops: 69 {
> > IN-HARDIRQ-W at:
> > lock_acquire+0x15f/0x420
> > _raw_spin_lock_irqsave+0x52/0xa0
> > ata_bmdma_interrupt+0x27/0x200
> > __handle_irq_event_percpu+0xd5/0x2b0
> > handle_irq_event+0x57/0xb0
> > handle_edge_irq+0x8c/0x230
> > asm_call_irq_on_stack+0xf/0x20
> > common_interrupt+0x100/0x1c0
> > asm_common_interrupt+0x1e/0x40
> > native_safe_halt+0xe/0x10
> > arch_cpu_idle+0x15/0x20
> > default_idle_call+0x59/0x1c0
> > do_idle+0x22c/0x2c0
> > cpu_startup_entry+0x20/0x30
> > start_secondary+0x11d/0x150
> > secondary_startup_64_no_verify+0xa6/0xab
> > INITIAL USE at:
> > lock_acquire+0x15f/0x420
> > _raw_spin_lock_irqsave+0x52/0xa0
> > ata_dev_init+0x54/0xe0
> > ata_link_init+0x8b/0xd0
> > ata_port_alloc+0x1f1/0x210
> > ata_host_alloc+0xf1/0x130
> > ata_host_alloc_pinfo+0x14/0xb0
> > ata_pci_sff_prepare_host+0x41/0xa0
> > ata_pci_bmdma_prepare_host+0x14/0x30
> > piix_init_one+0x21f/0x600
> > local_pci_probe+0x48/0x80
> > pci_device_probe+0x105/0x1c0
> > really_probe+0x221/0x490
> > driver_probe_device+0xe9/0x160
> > device_driver_attach+0xb2/0xc0
> > __driver_attach+0x91/0x150
> > bus_for_each_dev+0x81/0xc0
> > driver_attach+0x1e/0x20
> > bus_add_driver+0x138/0x1f0
> > driver_register+0x91/0xf0
> > __pci_register_driver+0x73/0x80
> > piix_init+0x1e/0x2e
> > do_one_initcall+0x5f/0x2d0
> > kernel_init_freeable+0x26f/0x2cf
> > kernel_init+0xe/0x113
> > ret_from_fork+0x1f/0x30
> > }
> > ... key at: [<ffffffff83d9fdc0>] __key.6+0x0/0x10
> > ... acquired at:
> > __lock_acquire+0x9da/0x2370
> > lock_acquire+0x15f/0x420
> > _raw_spin_lock_irqsave+0x52/0xa0
> > ata_bmdma_interrupt+0x27/0x200
> > __handle_irq_event_percpu+0xd5/0x2b0
> > handle_irq_event+0x57/0xb0
> > handle_edge_irq+0x8c/0x230
> > asm_call_irq_on_stack+0xf/0x20
> > common_interrupt+0x100/0x1c0
> > asm_common_interrupt+0x1e/0x40
> > native_safe_halt+0xe/0x10
> > arch_cpu_idle+0x15/0x20
> > default_idle_call+0x59/0x1c0
> > do_idle+0x22c/0x2c0
> > cpu_startup_entry+0x20/0x30
> > start_secondary+0x11d/0x150
> > secondary_startup_64_no_verify+0xa6/0xab
> >
> > This lockdep splat is reported after:
> > commit e918188611f0 ("locking: More accurate annotations for read_lock()")
> >
> > To clarify:
> > - read-locks are recursive only in interrupt context (when
> > in_interrupt() returns true)
> > - after acquiring host->lock in CPU1, another cpu (i.e. CPU2) may call
> > write_lock(&trig->leddev_list_lock) that would be blocked by CPU0
> > that holds trig->leddev_list_lock in read-mode
> > - when CPU1 (ata_ac_complete()) tries to read-lock
> > trig->leddev_list_lock, it would be blocked by the write-lock waiter
> > on CPU2 (because we are not in interrupt context, so the read-lock is
> > not recursive)
> > - at this point if an interrupt happens on CPU0 and
> > ata_bmdma_interrupt() is executed it will try to acquire host->lock,
> > that is held by CPU1, that is currently blocked by CPU2, so:
> >
> > * CPU0 blocked by CPU1
> > * CPU1 blocked by CPU2
> > * CPU2 blocked by CPU0
> >
> > *** DEADLOCK ***
> >
> > The deadlock scenario is better represented by the following schema
> > (thanks to Boqun Feng <boqun.feng@xxxxxxxxx> for the schema and the
> > detailed explanation of the deadlock condition):
> >
> > CPU 0: CPU 1: CPU 2:
> > ----- ----- -----
> > led_trigger_event():
> > read_lock(&trig->leddev_list_lock);
> > <workqueue>
> > ata_hsm_qc_complete():
> > spin_lock_irqsave(&host->lock);
> > write_lock(&trig->leddev_list_lock);
> > ata_port_freeze():
> > ata_do_link_abort():
> > ata_qc_complete():
> > ledtrig_disk_activity():
> > led_trigger_blink_oneshot():
> > read_lock(&trig->leddev_list_lock);
> > // ^ not in in_interrupt() context, so could get blocked by CPU 2
> > <interrupt>
> > ata_bmdma_interrupt():
> > spin_lock_irqsave(&host->lock);
> >
> > Fix by using read_lock_irqsave/irqrestore() in led_trigger_event(), so
> > that no interrupt can happen in between, preventing the deadlock
> > condition.
> >
> > Link: https://lore.kernel.org/lkml/20201101092614.GB3989@xps-13-7390/
> > Fixes: eb25cb9956cc ("leds: convert IDE trigger to common disk trigger")
> > Signed-off-by: Andrea Righi <andrea.righi@xxxxxxxxxxxxx>
>
> I'd hate to see this in stable 3 days after Linus merges it...
>
> Do these need _irqsave, too?
>
> drivers/leds/led-triggers.c: read_lock(&trig->leddev_list_lock);
> drivers/leds/led-triggers.c: read_unlock(&trig->leddev_list_lock);
> drivers/leds/led-triggers.c: read_lock(&trig->leddev_list_lock);
> drivers/leds/led-triggers.c: read_unlock(&trig->leddev_list_lock);
>

I think so, if you mean the read_{un,}lock in led_trigger_blink_setup()
also need to convert to irq-safe version ;-)

Regards,
Boqun

> Best regards,
> Pavel
>
> > ---
> > drivers/leds/led-triggers.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
> > index 91da90cfb11d..16d1a93a10a8 100644
> > --- a/drivers/leds/led-triggers.c
> > +++ b/drivers/leds/led-triggers.c
> > @@ -378,14 +378,15 @@ void led_trigger_event(struct led_trigger *trig,
> > enum led_brightness brightness)
> > {
> > struct led_classdev *led_cdev;
> > + unsigned long flags;
> >
> > if (!trig)
> > return;
> >
> > - read_lock(&trig->leddev_list_lock);
> > + read_lock_irqsave(&trig->leddev_list_lock, flags);
> > list_for_each_entry(led_cdev, &trig->led_cdevs, trig_list)
> > led_set_brightness(led_cdev, brightness);
> > - read_unlock(&trig->leddev_list_lock);
> > + read_unlock_irqrestore(&trig->leddev_list_lock, flags);
> > }
> > EXPORT_SYMBOL_GPL(led_trigger_event);
> >
>
> --
> http://www.livejournal.com/~pavelmachek

Next message: tip-bot2 for Peter Zijlstra: "[tip: sched/core] smp: Cleanup smp_call_function*()"
Previous message: Mark Brown: "Re: [PATCH] spi: dw: Fix spi registration for controllers overriding CS"
In reply to: Pavel Machek: "Re: [PATCH] leds: trigger: fix potential deadlock with libata"
Next in thread: Andrea Righi: "Re: [PATCH] leds: trigger: fix potential deadlock with libata"
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