From 34cb27528398738bea94852b99ef8fb05944ec41 Mon Sep 17 00:00:00 2001 From: Vitalii Demianets Date: Thu, 20 Jun 2013 16:36:00 +0300 Subject: [PATCH] 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 Reviewed-by: Pavel Machek Signed-off-by: Greg Kroah-Hartman --- drivers/uio/uio_pdrv_genirq.c | 18 +++++++++++++----- 1 file 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); -- 2.30.2