• Mika Westerberg's avatar
    pinctrl: baytrail: Use raw_spinlock for locking · 709adbf0
    Mika Westerberg authored
    commit 78e1c896 upstream.
    
    The Intel Baytrail pinctrl driver implements irqchip callbacks which are
    called with desc->lock raw_spinlock held. In mainline this is fine because
    spinlock resolves to raw_spinlock. However, running the same code in -rt we
    get:
    
     BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917
     in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: swapper/0
     Preemption disabled at:[<ffffffff81092e9f>] cpu_startup_entry+0x17f/0x480
    
     CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.1.5-rt5 #13
      ...
     Call Trace:
      <IRQ>  [<ffffffff816283c6>] dump_stack+0x4a/0x61
      [<ffffffff81077e17>] ___might_sleep+0xe7/0x170
      [<ffffffff8162d6cf>] rt_spin_lock+0x1f/0x50
      [<ffffffff812e3b88>] byt_gpio_clear_triggering+0x38/0x60
      [<ffffffff812e3bc1>] byt_irq_mask+0x11/0x20
      [<ffffffff810a7013>] handle_level_irq+0x83/0x150
      [<ffffffff810a3457>] generic_handle_irq+0x27/0x40
      [<ffffffff812e3a5f>] byt_gpio_irq_handler+0x7f/0xc0
      [<ffffffff810050aa>] handle_irq+0xaa/0x190
      ...
    
    This is because in -rt spinlocks are preemptible so taking the driver
    private spinlock in irqchip callbacks causes might_sleep() to trigger.
    
    In order to keep -rt happy but at the same time make sure that register
    accesses get serialized, convert the driver to use raw_spinlock instead.
    
    Also shorten the critical section a bit in few places.
    Suggested-by: default avatarLinus Walleij <linus.walleij@linaro.org>
    Signed-off-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
    Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
    Cc: Lucas De Marchi <lucas.de.marchi@gmail.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    709adbf0
pinctrl-baytrail.c 19.1 KB