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UIO: Fix concurrency issue

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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: Vitalii Demianets <vitas@nppfactor.kiev.ua>
Reviewed-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Vitalii Demianets 2013-06-20 16:36:00 +03:00 committed by Greg Kroah-Hartman
parent 077797117d
commit 34cb275283
1 changed files with 13 additions and 5 deletions
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18
drivers/uio/uio_pdrv_genirq.c
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@ -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);