Subject: Re: [ipw3945-devel] [PATCH 2/5] iwlwifi: iwl3945 synchronize interruptand tasklet for down iwlwifi

From: Joonwoo Park <[email-masked]>
Date: Mon, 14 Jan 2008 17:35:11 +0900

Joonwoo Park wrote:
> 2008/1/11, Chatre, Reinette <[email-masked]>:
>> On Thursday, January 10, 2008 5:25 PM, Joonwoo Park  wrote:
> 
>> What modification are you considering?
> 
> Roughly, I'm considering make synchronize_irq() be moved into
> iwl_disable_interrupts() and fix iwl_irq_tasket not to call
> iwl_disable_interrupts with irq disabled.
> For now iwl_irq_tasklet calls iwl_disable_interrupts() with local irq disabled.
> like this:
> 
> static void iwl_irq_tasklet(struct iwl_priv *priv)
> {
>         ...
>         spin_lock_irqsave(&priv->lock, flags);
> 
>         ...
>         /* Now service all interrupt bits discovered above. */
>         if (inta & CSR_INT_BIT_HW_ERR) {
>                 IWL_ERROR("Microcode HW error detected.  Restarting.\n");
> 
>                 /* Tell the device to stop sending interrupts */
>                 iwl_disable_interrupts(priv);
>                 ...
>                 spin_unlock_irqrestore(&priv->lock, flags);
>                 return;
>         }
> 
> 

After disabling interrupts, it's possible irq & tasklet is pending or running
This patch eleminates races for down iwlwifi

Since synchronize_irq can introduce iwl_irq_tasklet, tasklet_kill
should be called after doing synchronize_irq
To avoid races between iwl_synchronize_irq and iwl_irq_tasklet STATUS_INT_ENABLED
flag is needed.

Signed-off-by: Joonwoo Park <[email-masked]>
---
   drivers/net/wireless/iwlwifi/iwl3945-base.c |   33 ++++++++++++++++++++++-----
   1 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/iwlwifi/iwl3945-base.c b/drivers/net/wireless/iwlwifi/iwl3945-base.c
index 6e20725..f98cd4f 100644
--- a/drivers/net/wireless/iwlwifi/iwl3945-base.c
+++ b/drivers/net/wireless/iwlwifi/iwl3945-base.c
@@ -4405,6 +4405,14 @@ static void iwl_print_rx_config_cmd(struct iwl_rxon_cmd *rxon)
   }
   #endif

+static void iwl_synchronize_interrupts(struct iwl_priv *priv)
+{
+	synchronize_irq(priv->pci_dev->irq);
+	/* synchornize_irq introduces irq_tasklet,
+	 * tasklet_kill should be called after doing synchronize_irq */
+	tasklet_kill(&priv->irq_tasklet);
+}
+
   static void iwl_enable_interrupts(struct iwl_priv *priv)
   {
   	IWL_DEBUG_ISR("Enabling interrupts\n");
@@ -4413,7 +4421,7 @@ static void iwl_enable_interrupts(struct iwl_priv *priv)
   	iwl_flush32(priv, CSR_INT_MASK);
   }

-static inline void iwl_disable_interrupts(struct iwl_priv *priv)
+static inline void __iwl_disable_interrupts(struct iwl_priv *priv)
   {
   	clear_bit(STATUS_INT_ENABLED, &priv->status);

@@ -4427,6 +4435,13 @@ static inline void iwl_disable_interrupts(struct iwl_priv *priv)
   	iwl_flush32(priv, CSR_INT);
   	iwl_write32(priv, CSR_FH_INT_STATUS, 0xffffffff);
   	iwl_flush32(priv, CSR_FH_INT_STATUS);
+}
+
+static inline void iwl_disable_interrupts(struct iwl_priv *priv)
+{
+	__iwl_disable_interrupts(priv);
+
+	iwl_synchronize_interrupts(priv);

   	IWL_DEBUG_ISR("Disabled interrupts\n");
   }
@@ -4708,7 +4723,8 @@ static void iwl_irq_tasklet(struct iwl_priv *priv)
   		IWL_ERROR("Microcode HW error detected.  Restarting.\n");

   		/* Tell the device to stop sending interrupts */
-		iwl_disable_interrupts(priv);
+		__iwl_disable_interrupts(priv);
+		IWL_DEBUG_ISR("Disabled interrupts\n");

   		iwl_irq_handle_error(priv);

@@ -4814,8 +4830,11 @@ static void iwl_irq_tasklet(struct iwl_priv *priv)
   		IWL_WARNING("   with FH_INT = 0x%08x\n", inta_fh);
   	}

-	/* Re-enable all interrupts */
-	iwl_enable_interrupts(priv);
+	/* To avoid race when device goes down,
+	 * it should be discarded to enable interrupts */
+	if (test_bit(STATUS_INT_ENABLED, &priv->status))
+		/* Re-enable all interrupts */
+		iwl_enable_interrupts(priv);

   #ifdef CONFIG_IWLWIFI_DEBUG
   	if (iwl_debug_level & (IWL_DL_ISR)) {
@@ -4876,8 +4895,10 @@ unplugged:
   	return IRQ_HANDLED;

    none:
-	/* re-enable interrupts here since we don't have anything to service. */
-	iwl_enable_interrupts(priv);
+	if (test_bit(STATUS_INT_ENABLED, &priv->status))
+		/* re-enable interrupts here since we don't have anything
+		 * to service. */
+		iwl_enable_interrupts(priv);
   	spin_unlock(&priv->lock);
   	return IRQ_NONE;
   }
---

Thanks,
Joonwoo