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SubjectRe: [PATCH 0/16] DMA-API debugging facility v3
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Date
Where we complain about a discrepancy between unmap/sync and the
original mapping, it can sometimes be useful to see the backtrace of the
code which _mapped_ the region originally.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
---
Untested. Builds though. Thanks Johannes for pointing me at an example.
diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 9c1a498..79542db 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -26,6 +26,7 @@
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/list.h>
+#include <linux/stacktrace.h>
#include <linux/slab.h>

#define HASH_SIZE 256
@@ -39,6 +40,8 @@ enum {
dma_debug_coherent,
};

+#define DMA_DEBUG_STACKTRACE_ENTRIES 5
+
struct dma_debug_entry {
struct list_head list;
struct device *dev;
@@ -47,6 +50,10 @@ struct dma_debug_entry {
u64 dev_addr;
u64 size;
int direction;
+#ifdef CONFIG_STACKTRACE
+ struct stack_trace stacktrace;
+ unsigned long st_entries[DMA_DEBUG_STACKTRACE_ENTRIES];
+#endif
};

struct hash_bucket {
@@ -106,13 +113,24 @@ static const char *dir2name[4] = { "DMA_BIDIRECTIONAL", "DMA_TO_DEVICE",
* system log than the user configured. This variable is
* writeable via debugfs.
*/
-#define err_printk(dev, format, arg...) do { \
+static inline void dump_entry_trace(struct dma_debug_entry *entry)
+{
+#ifdef CONFIG_STACKTRACE
+ if (entry) {
+ printk(KERN_WARNING "Mapped at:\n");
+ print_stack_trace(&entry->stacktrace, 0);
+ }
+#endif
+}
+
+#define err_printk(dev, entry, format, arg...) do { \
error_count += 1; \
if (show_all_errors || show_num_errors > 0) { \
WARN(1, "%s %s: " format, \
dev_driver_string(dev), \
dev_name(dev) , ## arg); \
} \
+ dump_entry_trace(entry); \
if (!show_all_errors && show_num_errors > 0) \
show_num_errors -= 1; \
} while (0);
@@ -258,6 +276,12 @@ static struct dma_debug_entry *dma_entry_alloc(void)
list_del(&entry->list);
memset(entry, 0, sizeof(*entry));

+#ifdef CONFIG_STACKTRACE
+ entry->stacktrace.max_entries = DMA_DEBUG_STACKTRACE_ENTRIES;
+ entry->stacktrace.entries = entry->st_entries;
+ entry->stacktrace.skip = 1;
+ save_stack_trace(&entry->stacktrace);
+#endif
num_free_entries -= 1;
if (num_free_entries < min_free_entries)
min_free_entries = num_free_entries;
@@ -455,7 +479,7 @@ static void check_unmap(struct dma_debug_entry *ref)
entry = hash_bucket_find(bucket, ref);

if (!entry) {
- err_printk(ref->dev, "DMA-API: device driver tries "
+ err_printk(ref->dev, NULL, "DMA-API: device driver tries "
"to free DMA memory it has not allocated "
"[device address=0x%016llx] [size=%llu bytes]\n",
ref->dev_addr, ref->size);
@@ -463,7 +487,7 @@ static void check_unmap(struct dma_debug_entry *ref)
}

if (ref->size != entry->size) {
- err_printk(ref->dev, "DMA-API: device driver frees "
+ err_printk(ref->dev, entry, "DMA-API: device driver frees "
"DMA memory with different size "
"[device address=0x%016llx] [map size=%llu bytes] "
"[unmap size=%llu bytes]\n",
@@ -471,7 +495,7 @@ static void check_unmap(struct dma_debug_entry *ref)
}

if (ref->type != entry->type) {
- err_printk(ref->dev, "DMA-API: device driver frees "
+ err_printk(ref->dev, entry, "DMA-API: device driver frees "
"DMA memory with wrong function "
"[device address=0x%016llx] [size=%llu bytes] "
"[mapped as %s] [unmapped as %s]\n",
@@ -479,7 +503,7 @@ static void check_unmap(struct dma_debug_entry *ref)
type2name[entry->type], type2name[ref->type]);
} else if ((entry->type == dma_debug_coherent) &&
(ref->paddr != entry->paddr)) {
- err_printk(ref->dev, "DMA-API: device driver frees "
+ err_printk(ref->dev, entry, "DMA-API: device driver frees "
"DMA memory with different CPU address "
"[device address=0x%016llx] [size=%llu bytes] "
"[cpu alloc address=%p] [cpu free address=%p]",
@@ -492,7 +516,7 @@ static void check_unmap(struct dma_debug_entry *ref)
* DMA API don't handle this properly, so check for it here
*/
if (ref->direction != entry->direction) {
- err_printk(ref->dev, "DMA-API: device driver frees "
+ err_printk(ref->dev, entry, "DMA-API: device driver frees "
"DMA memory with different direction "
"[device address=0x%016llx] [size=%llu bytes] "
"[mapped with %s] [unmapped with %s]\n",
@@ -511,8 +535,8 @@ out:
static void check_for_stack(struct device *dev, void *addr)
{
if (object_is_on_stack(addr))
- err_printk(dev, "DMA-API: device driver maps memory from stack"
- " [addr=%p]\n", addr);
+ err_printk(dev, NULL, "DMA-API: device driver maps memory from"
+ "stack [addr=%p]\n", addr);
}

static void check_sync(struct device *dev, dma_addr_t addr,
@@ -533,7 +557,7 @@ static void check_sync(struct device *dev, dma_addr_t addr,
entry = hash_bucket_find(bucket, &ref);

if (!entry) {
- err_printk(dev, "DMA-API: device driver tries "
+ err_printk(dev, NULL, "DMA-API: device driver tries "
"to sync DMA memory it has not allocated "
"[device address=0x%016llx] [size=%llu bytes]\n",
addr, size);
@@ -541,7 +565,7 @@ static void check_sync(struct device *dev, dma_addr_t addr,
}

if ((offset + size) > entry->size) {
- err_printk(dev, "DMA-API: device driver syncs"
+ err_printk(dev, entry, "DMA-API: device driver syncs"
" DMA memory outside allocated range "
"[device address=0x%016llx] "
"[allocation size=%llu bytes] [sync offset=%llu] "
@@ -550,7 +574,7 @@ static void check_sync(struct device *dev, dma_addr_t addr,
}

if (direction != entry->direction) {
- err_printk(dev, "DMA-API: device driver syncs "
+ err_printk(dev, entry, "DMA-API: device driver syncs "
"DMA memory with different direction "
"[device address=0x%016llx] [size=%llu bytes] "
"[mapped with %s] [synced with %s]\n",
@@ -564,7 +588,7 @@ static void check_sync(struct device *dev, dma_addr_t addr,

if (to_cpu && !(entry->direction == DMA_FROM_DEVICE) &&
!(direction == DMA_TO_DEVICE))
- err_printk(dev, "DMA-API: device driver syncs "
+ err_printk(dev, entry, "DMA-API: device driver syncs "
"device read-only DMA memory for cpu "
"[device address=0x%016llx] [size=%llu bytes] "
"[mapped with %s] [synced with %s]\n",
@@ -574,7 +598,7 @@ static void check_sync(struct device *dev, dma_addr_t addr,

if (!to_cpu && !(entry->direction == DMA_TO_DEVICE) &&
!(direction == DMA_FROM_DEVICE))
- err_printk(dev, "DMA-API: device driver syncs "
+ err_printk(dev, entry, "DMA-API: device driver syncs "
"device write-only DMA memory to device "
"[device address=0x%016llx] [size=%llu bytes] "
"[mapped with %s] [synced with %s]\n",
--
David Woodhouse Open Source Technology Centre
David.Woodhouse@intel.com Intel Corporation



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