[patch V2 03/29] lib/stackdepot: Provide functions which operate on plain storage arrays

Thomas Gleixner
2019-04-18T08:41:22Z

The struct stack_trace indirection in the stack depot functions is a truly
pointless excercise which requires horrible code at the callsites.

Provide interfaces based on plain storage arrays.

Signed-off-by: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
Acked-by: Alexander Potapenko <glider-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
---
include/linux/stackdepot.h | 4 ++
lib/stackdepot.c | 66 ++++++++++++++++++++++++++++++++-------------
2 files changed, 51 insertions(+), 19 deletions(-)

--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -26,7 +26,11 @@ typedef u32 depot_stack_handle_t;
struct stack_trace;

depot_stack_handle_t depot_save_stack(struct stack_trace *trace, gfp_t flags);
+depot_stack_handle_t stack_depot_save(unsigned long *entries,
+ unsigned int nr_entries, gfp_t gfp_flags);

void depot_fetch_stack(depot_stack_handle_t handle, struct stack_trace *trace);
+unsigned int stack_depot_fetch(depot_stack_handle_t handle,
+ unsigned long **entries);

#endif
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -194,40 +194,56 @@ static inline struct stack_record *find_
return NULL;
}

-void depot_fetch_stack(depot_stack_handle_t handle, struct stack_trace *trace)
+/**
+ * stack_depot_fetch - Fetch stack entries from a depot
+ *
+ * @entries: Pointer to store the entries address
+ */
+unsigned int stack_depot_fetch(depot_stack_handle_t handle,
+ unsigned long **entries)
{
union handle_parts parts = { .handle = handle };
void *slab = stack_slabs[parts.slabindex];
size_t offset = parts.offset << STACK_ALLOC_ALIGN;
struct stack_record *stack = slab + offset;

- trace->nr_entries = trace->max_entries = stack->size;
- trace->entries = stack->entries;
- trace->skip = 0;
+ *entries = stack->entries;
+ return stack->size;
+}
+EXPORT_SYMBOL_GPL(stack_depot_fetch);
+
+void depot_fetch_stack(depot_stack_handle_t handle, struct stack_trace *trace)
+{
+ unsigned int nent = stack_depot_fetch(handle, &trace->entries);
+
+ trace->max_entries = trace->nr_entries = nent;
}
EXPORT_SYMBOL_GPL(depot_fetch_stack);

/**
- * depot_save_stack - save stack in a stack depot.
- * @trace - the stacktrace to save.
- * @alloc_flags - flags for allocating additional memory if required.
+ * stack_depot_save - Save a stack trace from an array
*
- * Returns the handle of the stack struct stored in depot.
+ * @entries: Pointer to storage array
+ * @nr_entries: Size of the storage array
+ * @alloc_flags: Allocation gfp flags
+ *
+ * Returns the handle of the stack struct stored in depot
*/
-depot_stack_handle_t depot_save_stack(struct stack_trace *trace,
- gfp_t alloc_flags)
+depot_stack_handle_t stack_depot_save(unsigned long *entries,
+ unsigned int nr_entries,
+ gfp_t alloc_flags)
{
- u32 hash;
- depot_stack_handle_t retval = 0;
struct stack_record *found = NULL, **bucket;
- unsigned long flags;
+ depot_stack_handle_t retval = 0;
struct page *page = NULL;
void *prealloc = NULL;
+ unsigned long flags;
+ u32 hash;

- if (unlikely(trace->nr_entries == 0))
+ if (unlikely(nr_entries == 0))
goto fast_exit;

- hash = hash_stack(trace->entries, trace->nr_entries);
+ hash = hash_stack(entries, nr_entries);
bucket = &stack_table[hash & STACK_HASH_MASK];

/*
@@ -235,8 +251,8 @@ depot_stack_handle_t depot_save_stack(st
* The smp_load_acquire() here pairs with smp_store_release() to
* |bucket| below.
*/
- found = find_stack(smp_load_acquire(bucket), trace->entries,
- trace->nr_entries, hash);
+ found = find_stack(smp_load_acquire(bucket), entries,
+ nr_entries, hash);
if (found)
goto exit;

@@ -264,10 +280,10 @@ depot_stack_handle_t depot_save_stack(st

spin_lock_irqsave(&depot_lock, flags);

- found = find_stack(*bucket, trace->entries, trace->nr_entries, hash);
+ found = find_stack(*bucket, entries, nr_entries, hash);
if (!found) {
struct stack_record *new =
- depot_alloc_stack(trace->entries, trace->nr_entries,
+ depot_alloc_stack(entries, nr_entries,
hash, &prealloc, alloc_flags);
if (new) {
new->next = *bucket;
@@ -297,4 +313,16 @@ depot_stack_handle_t depot_save_stack(st
fast_exit:
return retval;
}
+EXPORT_SYMBOL_GPL(stack_depot_save);
+
+/**
+ * depot_save_stack - save stack in a stack depot.
+ * @trace - the stacktrace to save.
+ * @alloc_flags - flags for allocating additional memory if required.
+ */
+depot_stack_handle_t depot_save_stack(struct stack_trace *trace,
+ gfp_t alloc_flags)
+{
+ return stack_depot_save(trace->entries, trace->nr_entries, alloc_flags);
+}
EXPORT_SYMBOL_GPL(depot_save_stack);