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 <vi...@nppfactor.kiev.ua>
---
drivers/uio/uio_pdrv_genirq.c | 13 ++++++++-----
1 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/drivers/uio/uio_pdrv_genirq.c b/drivers/uio/uio_pdrv_genirq.c
index cc5233b..8075367 100644
--- a/drivers/uio/uio_pdrv_genirq.c
+++ b/drivers/uio/uio_pdrv_genirq.c
@@ -68,8 +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(UIO_IRQ_DISABLED, &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;
}
@@ -83,16 +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(UIO_IRQ_DISABLED, &priv->flags))
+ if (__test_and_clear_bit(UIO_IRQ_DISABLED, &priv->flags))
enable_irq(dev_info->irq);
} else {
- if (!test_and_set_bit(UIO_IRQ_DISABLED, &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);
--
1.7.8.6
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