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Commit 34cb2752 authored by Vitalii Demianets's avatar Vitalii Demianets Committed by Greg Kroah-Hartman
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UIO: Fix concurrency issue 



In a SMP case there was a race condition issue between
uio_pdrv_genirq_irqcontrol() running on one CPU and irq handler on
another CPU. Fix it by spin_locking shared resources access inside irq
handler.  Also:
  - Change disable_irq to disable_irq_nosync to avoid deadlock, because
    disable_irq waits for the completion of the irq handler;
  - Change atomic bit-manipulation routines to their non-atomic
    counterparts as we already are guarding the code by spinlock.

Signed-off-by: default avatarVitalii Demianets <vitas@nppfactor.kiev.ua>
Reviewed-by: default avatarPavel Machek <pavel@ucw.cz>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 07779711

drivers/uio/uio_pdrv_genirq.c

+13 −5
Original line number Diff line number Diff line
@@ -37,6 +37,11 @@ struct uio_pdrv_genirq_platdata { 
	struct platform_device *pdev;

};



/* Bits in uio_pdrv_genirq_platdata.flags */

enum {

	UIO_IRQ_DISABLED = 0,

};



static int uio_pdrv_genirq_open(struct uio_info *info, struct inode *inode)

{

	struct uio_pdrv_genirq_platdata *priv = info->priv;
@@ -63,8 +68,10 @@ static irqreturn_t uio_pdrv_genirq_handler(int irq, struct uio_info *dev_info) 
	 * remember the state so we can allow user space to enable it later.

	 */



	if (!test_and_set_bit(0, &priv->flags))

	spin_lock(&priv->lock);

	if (!__test_and_set_bit(UIO_IRQ_DISABLED, &priv->flags))

		disable_irq_nosync(irq);

	spin_unlock(&priv->lock);



	return IRQ_HANDLED;

}
@@ -78,16 +85,17 @@ static int uio_pdrv_genirq_irqcontrol(struct uio_info *dev_info, s32 irq_on) 
	 * in the interrupt controller, but keep track of the

	 * state to prevent per-irq depth damage.

	 *

	 * Serialize this operation to support multiple tasks.

	 * Serialize this operation to support multiple tasks and concurrency

	 * with irq handler on SMP systems.

	 */



	spin_lock_irqsave(&priv->lock, flags);

	if (irq_on) {

		if (test_and_clear_bit(0, &priv->flags))

		if (__test_and_clear_bit(UIO_IRQ_DISABLED, &priv->flags))

			enable_irq(dev_info->irq);

	} else {

		if (!test_and_set_bit(0, &priv->flags))

			disable_irq(dev_info->irq);

		if (!__test_and_set_bit(UIO_IRQ_DISABLED, &priv->flags))

			disable_irq_nosync(dev_info->irq);

	}

	spin_unlock_irqrestore(&priv->lock, flags);