[v2,13/18] lib/stackdepot: annotate depot_init_pool and depot_alloc_stack
Commit Message
From: Andrey Konovalov <andreyknvl@google.com>
Clean up the exisiting comments and add new ones to depot_init_pool and
depot_alloc_stack.
As a part of the clean-up, remove mentions of which variable is accessed
by smp_store_release and smp_load_acquire: it is clear as is from the
code.
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
lib/stackdepot.c | 34 ++++++++++++++++++++++++----------
1 file changed, 24 insertions(+), 10 deletions(-)
Comments
On Fri, Feb 10, 2023 at 10:18 PM <andrey.konovalov@linux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@google.com>
>
> Clean up the exisiting comments and add new ones to depot_init_pool and
> depot_alloc_stack.
>
> As a part of the clean-up, remove mentions of which variable is accessed
> by smp_store_release and smp_load_acquire: it is clear as is from the
> code.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Thanks for the cleanup!
@@ -218,32 +218,39 @@ int stack_depot_init(void)
}
EXPORT_SYMBOL_GPL(stack_depot_init);
+/* Uses preallocated memory to initialize a new stack depot pool. */
static void depot_init_pool(void **prealloc)
{
/*
- * This smp_load_acquire() pairs with smp_store_release() to
- * |next_pool_inited| below and in depot_alloc_stack().
+ * smp_load_acquire() here pairs with smp_store_release() below and
+ * in depot_alloc_stack().
*/
if (smp_load_acquire(&next_pool_inited))
return;
+
+ /* Check if the current pool is not yet allocated. */
if (stack_pools[pool_index] == NULL) {
+ /* Use the preallocated memory for the current pool. */
stack_pools[pool_index] = *prealloc;
*prealloc = NULL;
} else {
- /* If this is the last depot pool, do not touch the next one. */
+ /*
+ * Otherwise, use the preallocated memory for the next pool
+ * as long as we do not exceed the maximum number of pools.
+ */
if (pool_index + 1 < DEPOT_MAX_POOLS) {
stack_pools[pool_index + 1] = *prealloc;
*prealloc = NULL;
}
/*
- * This smp_store_release pairs with smp_load_acquire() from
- * |next_pool_inited| above and in stack_depot_save().
+ * This smp_store_release pairs with smp_load_acquire() above
+ * and in stack_depot_save().
*/
smp_store_release(&next_pool_inited, 1);
}
}
-/* Allocation of a new stack in raw storage */
+/* Allocates a new stack in a stack depot pool. */
static struct stack_record *
depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
{
@@ -252,28 +259,35 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
required_size = ALIGN(required_size, 1 << DEPOT_STACK_ALIGN);
+ /* Check if there is not enough space in the current pool. */
if (unlikely(pool_offset + required_size > DEPOT_POOL_SIZE)) {
+ /* Bail out if we reached the pool limit. */
if (unlikely(pool_index + 1 >= DEPOT_MAX_POOLS)) {
WARN_ONCE(1, "Stack depot reached limit capacity");
return NULL;
}
+
+ /* Move on to the next pool. */
pool_index++;
pool_offset = 0;
/*
- * smp_store_release() here pairs with smp_load_acquire() from
- * |next_pool_inited| in stack_depot_save() and
- * depot_init_pool().
+ * smp_store_release() here pairs with smp_load_acquire() in
+ * stack_depot_save() and depot_init_pool().
*/
if (pool_index + 1 < DEPOT_MAX_POOLS)
smp_store_release(&next_pool_inited, 0);
}
+
+ /* Assign the preallocated memory to a pool if required. */
if (*prealloc)
depot_init_pool(prealloc);
+
+ /* Check if we have a pool to save the stack trace. */
if (stack_pools[pool_index] == NULL)
return NULL;
+ /* Save the stack trace. */
stack = stack_pools[pool_index] + pool_offset;
-
stack->hash = hash;
stack->size = size;
stack->handle.pool_index = pool_index;