Re: [PATCH 1/2] pinctrl: intel: Use raw_spinlock for locking

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Thu, Jun 16, 2016 at 10:25 AM, Mika Westerberg
<mika.westerberg@xxxxxxxxxxxxxxx> wrote:

> When running -rt kernel and GPIO interrupt happens we get following
>
>  BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:931
>  in_atomic(): 1, irqs_disabled(): 0, pid: 530, name: irq/14-INT3452:
>  Preemption disabled at:[<ffffffff810b4dab>] handle_edge_irq+0x1b/0x190
>
>  CPU: 0 PID: 530 Comm: irq/14-INT3452: Not tainted 4.6.2-rt5 #1060
>   0000000000000000 ffff88007a257d58 ffffffff812d8494 0000000000000000
>   ffff88017a330000 ffff88007a257d78 ffffffff81083a11 ffff88007a252430
>   ffff88007a252430 ffff88007a257d90 ffffffff8167ef20 000000000000001a
>  Call Trace:
>   [<ffffffff812d8494>] dump_stack+0x4f/0x6b
>   [<ffffffff81083a11>] ___might_sleep+0xe1/0x160
>   [<ffffffff8167ef20>] rt_spin_lock+0x20/0x50
>   [<ffffffff81308c6d>] intel_gpio_irq_ack+0x2d/0x80
>   [<ffffffff810b4e0b>] handle_edge_irq+0x7b/0x190
>   [<ffffffff810b0d82>] generic_handle_irq+0x22/0x30
>   [<ffffffff81307abc>] intel_gpio_irq+0xdc/0x150
>   [<ffffffff810b2293>] irq_forced_thread_fn+0x23/0x70
>   [<ffffffff810b250b>] irq_thread+0x13b/0x1d0
>   [<ffffffff8167b844>] ? __schedule+0x2e4/0x5a0
>   [<ffffffff810b2270>] ? irq_finalize_oneshot.part.37+0xd0/0xd0
>   [<ffffffff810b25a0>] ? irq_thread+0x1d0/0x1d0
>   [<ffffffff810b23d0>] ? wake_threads_waitq+0x30/0x30
>   [<ffffffff8107e624>] kthread+0xd4/0xf0
>   [<ffffffff8167ec27>] ? _raw_spin_unlock_irq+0x17/0x40
>   [<ffffffff8167f592>] ret_from_fork+0x22/0x40
>   [<ffffffff8107e550>] ? kthread_worker_fn+0x190/0x190
>
> The reason why this happens is because intel_gpio_irq_ack() is called with
> desc->lock raw_spinlock locked which cannot sleep but our normal spinlock
> (which is converted to rtmutex in -rt) is allowed to sleep. This causes
> might_sleep() to trigger.
>
> Fix this by converting the normal spinlock to a raw_spinlock.
>
> Reported-by: Kim Tatt Chuah <kim.tatt.chuah@xxxxxxxxx>
> Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>

Patch applied for fixes.

Yours,
Linus Walleij
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