dma-debug: print information about leaked entry

PATCH Applied Stanislaw Gruszka 3 participants 3 messages Mar 31, 2011 – May 11, 2011 Library code

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Stanislaw Gruszka

author

2011-03-31 12:09 UTC #0 lore raw

PATCH 1/1 dma-debug: print information about leaked entry

When driver leak dma mapping, print additional information about one of leaked entries, to to help investigate problem. Patch should be useful for debugging drivers, which maps many different class of buffers.

Signed-off-by Stanislaw Gruszka <[email protected]>

---
 lib/dma-debug.c |   18 +++++++++++++-----
 1 files changed, 13 insertions(+), 5 deletions(-)

lib/dma-debug.c +13 -5

index 4bfb047..db07bfd 100644
@@ -649,7 +649,7 @@ out_err:
 	return -ENOMEM;
 }
 
-static int device_dma_allocations(struct device *dev)
+static int device_dma_allocations(struct device *dev, struct dma_debug_entry **out_entry)
 {
 	struct dma_debug_entry *entry;
 	unsigned long flags;

@@ -660,8 +660,10 @@ static int device_dma_allocations(struct device *dev)
 	for (i = 0; i < HASH_SIZE; ++i) {
 		spin_lock(&dma_entry_hash[i].lock);
 		list_for_each_entry(entry, &dma_entry_hash[i].list, list) {
-			if (entry->dev == dev)
+			if (entry->dev == dev) {
 				count += 1;
+				*out_entry = entry;
+			}
 		}
 		spin_unlock(&dma_entry_hash[i].lock);
 	}

@@ -674,6 +676,7 @@ static int device_dma_allocations(struct device *dev)
 static int dma_debug_device_change(struct notifier_block *nb, unsigned long action, void *data)
 {
 	struct device *dev = data;
+	struct dma_debug_entry *uninitialized_var(entry);
 	int count;
 
 	if (global_disable)

@@ -681,12 +684,17 @@ static int dma_debug_device_change(struct notifier_block *nb, unsigned long acti
 
 	switch (action) {
 	case BUS_NOTIFY_UNBOUND_DRIVER:
-		count = device_dma_allocations(dev);
+		count = device_dma_allocations(dev, &entry);
 		if (count == 0)
 			break;
-		err_printk(dev, NULL, "DMA-API: device driver has pending "
+		err_printk(dev, entry, "DMA-API: device driver has pending "
 				"DMA allocations while released from device "
-				"[count=%d]\n", count);
+				"[count=%d]\n"
+				"One of leaked entries details: "
+				"[device address=0x%016llx] [size=%llu bytes] "
+				"[mapped with %s] [mapped as %s]\n",
+			count, entry->dev_addr, entry->size,
+			dir2name[entry->direction], type2name[entry->type]);
 		break;
 	default:
 		break;

Signature · 1 line

1.7.1

Roedel, Joerg

Applied

2011-04-07 15:13 UTC #1 lore raw

Quoted 5 lines · Stanislaw Gruszka

When driver leak dma mapping, print additional information about one of leaked entries, to to help investigate problem. Patch should be useful for debugging drivers, which maps many different class of buffers.
Signed-off-by Stanislaw Gruszka <[email protected]>

Applied, thanks.

Signature · 5 lines

AMD Operating System Research Center

Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo, Andrew Bowd
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632

Andrew Morton

maintainer

2011-05-11 00:13 UTC #2 lore raw

In reply to Stanislaw Gruszka

Quoted 35 lines · On Thu, 31 Mar 2011 14:08:09 +0200 Stanislaw Gruszka <[email protected]>…

Signed-off-by Stanislaw Gruszka <[email protected]>

---
 lib/dma-debug.c |   18 +++++++++++++-----
 1 files changed, 13 insertions(+), 5 deletions(-)

lib/dma-debug.c +4 -2

index 4bfb047..db07bfd 100644
@@ -649,7 +649,7 @@ out_err:
 	return -ENOMEM;
 }
 
-static int device_dma_allocations(struct device *dev)
+static int device_dma_allocations(struct device *dev, struct dma_debug_entry **out_entry)
 {
 	struct dma_debug_entry *entry;
 	unsigned long flags;

@@ -660,8 +660,10 @@ static int device_dma_allocations(struct device *dev)
 	for (i = 0; i < HASH_SIZE; ++i) {
 		spin_lock(&dma_entry_hash[i].lock);
 		list_for_each_entry(entry, &dma_entry_hash[i].list, list) {
-			if (entry->dev == dev)
+			if (entry->dev == dev) {
 				count += 1;
+				*out_entry = entry;
+			}
 		}
 		spin_unlock(&dma_entry_hash[i].lock);
 	}

lib/dma-debug.c static int device_dma_allocations(struct device *dev) · line 679

Quoted 4 lines

lib/dma-debug.c +1 -0

@@ -674,6 +676,7 @@ static int device_dma_allocations(struct device *dev)
 static int dma_debug_device_change(struct notifier_block *nb, unsigned long action, void *data)
 {
 	struct device *dev = data;
+	struct dma_debug_entry *uninitialized_var(entry);

The warning you saw was due to gcc assuming that foo(&bar) might not write to `bar'. That was fixed (ie: suppressed) in later gcc's, so we tend not to bother working around it.

Quoted 11 lines

lib/dma-debug.c +1 -1

 	int count;
 
 	if (global_disable)

@@ -681,12 +684,17 @@ static int dma_debug_device_change(struct notifier_block *nb, unsigned long acti
 
 	switch (action) {
 	case BUS_NOTIFY_UNBOUND_DRIVER:
-		count = device_dma_allocations(dev);
+		count = device_dma_allocations(dev, &entry);
 		if (count == 0)
 			break;

lib/dma-debug.c static int dma_debug_device_change(struct notifier_block *nb, unsigned long acti · line 697

Quoted 10 lines

lib/dma-debug.c +7 -2

-		err_printk(dev, NULL, "DMA-API: device driver has pending "
+		err_printk(dev, entry, "DMA-API: device driver has pending "
 				"DMA allocations while released from device "
-				"[count=%d]\n", count);
+				"[count=%d]\n"
+				"One of leaked entries details: "
+				"[device address=0x%016llx] [size=%llu bytes] "
+				"[mapped with %s] [mapped as %s]\n",
+			count, entry->dev_addr, entry->size,
+			dir2name[entry->direction], type2name[entry->type]);

hm, how does the programmer use this info. Does the device address identify the device and its driver? That seems a bit indirect.

ah, I see that the gruesome err_printk() does a WARN, so the stack backtrace will tell us where the problem is occurring.