of: fix race when matching drivers

If two drivers are probing devices at the same time, both will write their match table result to the dev->of_match cache at the same time. Only write the result if the device matches. In a thread titled "SBus devices sometimes detected, sometimes not", Meelis reported his SBus hme was not detected about 50% of the time. From the debug suggested by Grant it was obvious another driver matched some devices between the call to match the hme and the hme discovery failling. Reported-by: Meelis Roos <[email protected]> Signed-off-by: Milton Miller <[email protected]> [grant.likely: modified to only call of_match_device() once] Signed-off-by: Grant Likely <[email protected]>
RyanHsu · May 18, 2011 · 01294d8 · 01294d8
1 parent 2e9521f
commit 01294d8
Showing 1 changed file with 6 additions and 2 deletions.
diff --git a/include/linux/of_device.h b/include/linux/of_device.h
@@ -21,8 +21,12 @@ extern void of_device_make_bus_id(struct device *dev);
 static inline int of_driver_match_device(struct device *dev,
 					 const struct device_driver *drv)
 {
-	dev->of_match = of_match_device(drv->of_match_table, dev);
-	return dev->of_match != NULL;
+	const struct of_device_id *match;
+
+	match = of_match_device(drv->of_match_table, dev);
+	if (match)
+		dev->of_match = match;
+	return match != NULL;
 }
 
 extern struct platform_device *of_dev_get(struct platform_device *dev);