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authorVitalii Demianets <vitas@nppfactor.kiev.ua>2013-06-20 16:36:00 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-06-24 16:31:21 -0700
commit34cb27528398738bea94852b99ef8fb05944ec41 (patch)
tree88a9e99282138bd21af563b98ab65ccc8ab088be
parent077797117dfa209717e1f3f1416c1101c0e047f0 (diff)
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: Vitalii Demianets <vitas@nppfactor.kiev.ua> Reviewed-by: Pavel Machek <pavel@ucw.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/uio/uio_pdrv_genirq.c18
1 files changed, 13 insertions, 5 deletions
diff --git a/drivers/uio/uio_pdrv_genirq.c b/drivers/uio/uio_pdrv_genirq.c
index 97415492779e..bcd72f3a62c3 100644
--- a/drivers/uio/uio_pdrv_genirq.c
+++ b/drivers/uio/uio_pdrv_genirq.c
@@ -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);