[PATCH iwl-net 3/4] igb: split igb_msg_task()

[Wander Lairson Costa <wander@redhat.com>]

From the perspective of PREEMPT_RT, igb_msg_task() invokes functions
that are a mix of IRQ-safe and non-IRQ-safe operations.

To address this, we separate igb_msg_task() into distinct IRQ-safe and
preemptible-safe components. This is a preparatory step for upcoming
commits, where the igb_msix_other interrupt handler will be split into
IRQ and threaded handlers, each invoking the appropriate part of the
newly divided igb_msg_task().

Signed-off-by: Wander Lairson Costa <wander@redhat.com>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 88 +++++++++++++++++++++--
 1 file changed, 81 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 9b4235ec226df..5828831fd29c2 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -149,6 +149,8 @@ static int igb_vlan_rx_kill_vid(struct net_device *, __be16, u16);
 static void igb_restore_vlan(struct igb_adapter *);
 static void igb_rar_set_index(struct igb_adapter *, u32);
 static void igb_ping_all_vfs(struct igb_adapter *);
+static void igb_msg_task_irq_safe(struct igb_adapter *adapter);
+static void igb_msg_task_preemptible_safe(struct igb_adapter *adapter);
 static void igb_msg_task(struct igb_adapter *);
 static void igb_vmm_control(struct igb_adapter *);
 static int igb_set_vf_mac(struct igb_adapter *, int, unsigned char *);
@@ -3681,6 +3683,30 @@ static __always_inline void vfs_unlock_irqrestore(struct igb_adapter *adapter,
 	raw_spin_unlock_irqrestore(&adapter->raw_vfs_lock, flags);
 	spin_unlock_irqrestore(&adapter->vfs_lock, flags);
 }
+
+static __always_inline void vfs_spin_lock_irqsave(struct igb_adapter *adapter,
+						  unsigned long *flags)
+{
+	spin_lock_irqsave(&adapter->vfs_lock, *flags);
+}
+
+static __always_inline void vfs_spin_unlock_irqrestore(struct igb_adapter *adapter,
+						       unsigned long flags)
+{
+	spin_unlock_irqrestore(&adapter->vfs_lock, flags);
+}
+
+static __always_inline void vfs_raw_spin_lock_irqsave(struct igb_adapter *adapter,
+						      unsigned long *flags)
+{
+	raw_spin_lock_irqsave(&adapter->raw_vfs_lock, *flags);
+}
+
+static __always_inline void vfs_raw_spin_unlock_irqrestore(struct igb_adapter *adapter,
+							   unsigned long flags)
+{
+	raw_spin_unlock_irqrestore(&adapter->raw_vfs_lock, flags);
+}
 #else
 static __always_inline void vfs_lock_init(struct igb_adapter *adapter)
 {
@@ -3696,6 +3722,30 @@ static __always_inline void vfs_unlock_irqrestore(struct igb_adapter *adapter, u
 {
 	spin_unlock_irqrestore(&adapter->vfs_lock, flags);
 }
+
+static __always_inline void vfs_spin_lock_irqsave(struct igb_adapter *adapter,
+						  unsigned long *flags)
+{
+	spin_lock_irqsave(&adapter->vfs_lock, *flags);
+}
+
+static __always_inline void vfs_spin_unlock_irqrestore(struct igb_adapter *adapter,
+						       unsigned long flags)
+{
+	spin_unlock_irqrestore(&adapter->vfs_lock, flags);
+}
+
+static __always_inline void vfs_raw_spin_lock_irqsave(struct igb_adapter *adapter,
+						      unsigned long *flags)
+{
+	spin_lock_irqsave(&adapter->vfs_lock, *flags);
+}
+
+static __always_inline void vfs_raw_spin_unlock_irqrestore(struct igb_adapter *adapter,
+							   unsigned long flags)
+{
+	spin_unlock_irqrestore(&adapter->vfs_lock, flags);
+}
 #endif
 
 #ifdef CONFIG_PCI_IOV
@@ -8070,27 +8120,51 @@ static void igb_rcv_msg_from_vf(struct igb_adapter *adapter, u32 vf)
 	igb_unlock_mbx(hw, vf);
 }
 
-static void igb_msg_task(struct igb_adapter *adapter)
+/*
+ * Note: the split of irq and preempible safe parts of igb_msg_task()
+ * only makes sense under PREEMPT_RT.
+ * The root cause of igb_rcv_msg_from_vf() is not IRQ safe is because
+ * it calls kcalloc with GFP_ATOMIC, but GFP_ATOMIC is not IRQ safe
+ * in PREEMPT_RT.
+ */
+static void igb_msg_task_irq_safe(struct igb_adapter *adapter)
 {
 	struct e1000_hw *hw = &adapter->hw;
 	unsigned long flags;
 	u32 vf;
 
-	vfs_lock_irqsave(adapter, &flags);
+	vfs_raw_spin_lock_irqsave(adapter, &flags);
 	for (vf = 0; vf < adapter->vfs_allocated_count; vf++) {
 		/* process any reset requests */
 		if (!igb_check_for_rst(hw, vf))
 			igb_vf_reset_event(adapter, vf);
 
-		/* process any messages pending */
-		if (!igb_check_for_msg(hw, vf))
-			igb_rcv_msg_from_vf(adapter, vf);
-
 		/* process any acks */
 		if (!igb_check_for_ack(hw, vf))
 			igb_rcv_ack_from_vf(adapter, vf);
 	}
-	vfs_unlock_irqrestore(adapter, flags);
+	vfs_raw_spin_unlock_irqrestore(adapter, flags);
+}
+
+static void igb_msg_task_preemptible_safe(struct igb_adapter *adapter)
+{
+	struct e1000_hw *hw = &adapter->hw;
+	unsigned long flags;
+	u32 vf;
+
+	vfs_spin_lock_irqsave(adapter, &flags);
+	for (vf = 0; vf < adapter->vfs_allocated_count; vf++) {
+		/* process any messages pending */
+		if (!igb_check_for_msg(hw, vf))
+			igb_rcv_msg_from_vf(adapter, vf);
+	}
+	vfs_spin_unlock_irqrestore(adapter, flags);
+}
+
+static __always_inline void igb_msg_task(struct igb_adapter *adapter)
+{
+	igb_msg_task_irq_safe(adapter);
+	igb_msg_task_preemptible_safe(adapter);
 }
 
 /**
-- 
2.47.0