[PATCH 4/5 V4] PCI: only return true when dev io state is really changed

[Ethan Zhao]

When uncorrectable error happens, AER driver and DPC driver interrupt
handlers likely call

   pcie_do_recovery()
   ->pci_walk_bus()
     ->report_frozen_detected()

with pci_channel_io_frozen the same time.
   If pci_dev_set_io_state() return true even if the original state is
pci_channel_io_frozen, that will cause AER or DPC handler re-enter
the error detecting and recovery procedure one after another.
   The result is the recovery flow mixed between AER and DPC.
So simplify the pci_dev_set_io_state() function to only return true
when dev->error_state is changed.

Signed-off-by: Ethan Zhao <haifeng.zhao@xxxxxxxxx>
Tested-by: Wen Jin <wen.jin@xxxxxxxxx>
Tested-by: Shanshan Zhang <ShanshanX.Zhang@xxxxxxxxx>
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@xxxxxxxxx>
---
Changnes:
 V2: revise description and code according to suggestion from Andy.
 V3: change code to simpler.
 V4: no change.
 V5: no change.
 
 drivers/pci/pci.h | 37 +++++--------------------------------
 1 file changed, 5 insertions(+), 32 deletions(-)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index fa12f7cbc1a0..a2c1c7d5f494 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -359,39 +359,12 @@ struct pci_sriov {
 static inline bool pci_dev_set_io_state(struct pci_dev *dev,
 					pci_channel_state_t new)
 {
-	bool changed = false;
-
 	device_lock_assert(&dev->dev);
-	switch (new) {
-	case pci_channel_io_perm_failure:
-		switch (dev->error_state) {
-		case pci_channel_io_frozen:
-		case pci_channel_io_normal:
-		case pci_channel_io_perm_failure:
-			changed = true;
-			break;
-		}
-		break;
-	case pci_channel_io_frozen:
-		switch (dev->error_state) {
-		case pci_channel_io_frozen:
-		case pci_channel_io_normal:
-			changed = true;
-			break;
-		}
-		break;
-	case pci_channel_io_normal:
-		switch (dev->error_state) {
-		case pci_channel_io_frozen:
-		case pci_channel_io_normal:
-			changed = true;
-			break;
-		}
-		break;
-	}
-	if (changed)
-		dev->error_state = new;
-	return changed;
+	if (dev->error_state == new)
+		return false;
+
+	dev->error_state = new;
+	return true;
 }
 
 static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused)
-- 
2.18.4