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 18:42:42 +0900

I'm so sorry for mangled patch.
resending patch with preformat html from thunderbird.

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