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authorRobin Murphy <robin.murphy@arm.com>2018-12-10 14:00:29 +0000
committerChristoph Hellwig <hch@lst.de>2018-12-11 14:31:17 +0100
commit2b9d9ac02b9d8d32c515c82bb17401c429f160ab (patch)
tree8f224b9fe62c452686c7b781f8a742c78e619605 /kernel/dma
parentf737b095c60c635db260e02fdb9f0efb9f3360c4 (diff)
dma-debug: Dynamically expand the dma_debug_entry pool
Certain drivers such as large multi-queue network adapters can use pools of mapped DMA buffers larger than the default dma_debug_entry pool of 65536 entries, with the result that merely probing such a device can cause DMA debug to disable itself during boot unless explicitly given an appropriate "dma_debug_entries=..." option. Developers trying to debug some other driver on such a system may not be immediately aware of this, and at worst it can hide bugs if they fail to realise that dma-debug has already disabled itself unexpectedly by the time their code of interest gets to run. Even once they do realise, it can be a bit of a pain to emprirically determine a suitable number of preallocated entries to configure, short of massively over-allocating. There's really no need for such a static limit, though, since we can quite easily expand the pool at runtime in those rare cases that the preallocated entries are insufficient, which is arguably the least surprising and most useful behaviour. To that end, refactor the prealloc_memory() logic a little bit to generalise it for runtime reallocations as well. Signed-off-by: Robin Murphy <robin.murphy@arm.com> Tested-by: Qian Cai <cai@lca.pw> Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'kernel/dma')
-rw-r--r--kernel/dma/debug.c79
1 files changed, 41 insertions, 38 deletions
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 29486eb9d1dc..ef7c90b7a346 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -47,6 +47,8 @@
#ifndef PREALLOC_DMA_DEBUG_ENTRIES
#define PREALLOC_DMA_DEBUG_ENTRIES (1 << 16)
#endif
+/* If the pool runs out, add this many new entries at once */
+#define DMA_DEBUG_DYNAMIC_ENTRIES 256
enum {
dma_debug_single,
@@ -646,6 +648,34 @@ static void add_dma_entry(struct dma_debug_entry *entry)
*/
}
+static int dma_debug_create_entries(u32 num_entries, gfp_t gfp)
+{
+ struct dma_debug_entry *entry, *next_entry;
+ int i;
+
+ for (i = 0; i < num_entries; ++i) {
+ entry = kzalloc(sizeof(*entry), gfp);
+ if (!entry)
+ goto out_err;
+
+ list_add_tail(&entry->list, &free_entries);
+ }
+
+ num_free_entries += num_entries;
+ nr_total_entries += num_entries;
+
+ return 0;
+
+out_err:
+
+ list_for_each_entry_safe(entry, next_entry, &free_entries, list) {
+ list_del(&entry->list);
+ kfree(entry);
+ }
+
+ return -ENOMEM;
+}
+
static struct dma_debug_entry *__dma_entry_alloc(void)
{
struct dma_debug_entry *entry;
@@ -672,12 +702,14 @@ static struct dma_debug_entry *dma_entry_alloc(void)
unsigned long flags;
spin_lock_irqsave(&free_entries_lock, flags);
-
- if (list_empty(&free_entries)) {
- global_disable = true;
- spin_unlock_irqrestore(&free_entries_lock, flags);
- pr_err("debugging out of memory - disabling\n");
- return NULL;
+ if (num_free_entries == 0) {
+ if (dma_debug_create_entries(DMA_DEBUG_DYNAMIC_ENTRIES,
+ GFP_ATOMIC)) {
+ global_disable = true;
+ spin_unlock_irqrestore(&free_entries_lock, flags);
+ pr_err("debugging out of memory - disabling\n");
+ return NULL;
+ }
}
entry = __dma_entry_alloc();
@@ -764,36 +796,6 @@ int dma_debug_resize_entries(u32 num_entries)
* 2. Preallocate a given number of dma_debug_entry structs
*/
-static int prealloc_memory(u32 num_entries)
-{
- struct dma_debug_entry *entry, *next_entry;
- int i;
-
- for (i = 0; i < num_entries; ++i) {
- entry = kzalloc(sizeof(*entry), GFP_KERNEL);
- if (!entry)
- goto out_err;
-
- list_add_tail(&entry->list, &free_entries);
- }
-
- num_free_entries = num_entries;
- min_free_entries = num_entries;
-
- pr_info("preallocated %d debug entries\n", num_entries);
-
- return 0;
-
-out_err:
-
- list_for_each_entry_safe(entry, next_entry, &free_entries, list) {
- list_del(&entry->list);
- kfree(entry);
- }
-
- return -ENOMEM;
-}
-
static ssize_t filter_read(struct file *file, char __user *user_buf,
size_t count, loff_t *ppos)
{
@@ -1038,14 +1040,15 @@ static int dma_debug_init(void)
return 0;
}
- if (prealloc_memory(nr_prealloc_entries) != 0) {
+ if (dma_debug_create_entries(nr_prealloc_entries, GFP_KERNEL) != 0) {
pr_err("debugging out of memory error - disabled\n");
global_disable = true;
return 0;
}
- nr_total_entries = num_free_entries;
+ min_free_entries = num_free_entries;
+ pr_info("preallocated %d debug entries\n", nr_total_entries);
dma_debug_initialized = true;