From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Clean up the exisiting comments and add new ones to depot_init_slab 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@xxxxxxxxxx>
---
lib/stackdepot.c | 35 +++++++++++++++++++++++++----------
1 file changed, 25 insertions(+), 10 deletions(-)
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index d6be82a5c223..7282565722f2 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -218,33 +218,41 @@ int stack_depot_init(void)
}
EXPORT_SYMBOL_GPL(stack_depot_init);
+/* Uses preallocated memory to initialize a new stack depot slab. */
static void depot_init_slab(void **prealloc)
{
/*
- * This smp_load_acquire() pairs with smp_store_release() to
- * |next_slab_inited| below and in depot_alloc_stack().
+ * If the next slab is already initialized, do not use the
+ * preallocated memory.
+ * smp_load_acquire() here pairs with smp_store_release() below and
+ * in depot_alloc_stack().
*/
if (smp_load_acquire(&next_slab_inited))
return;
+
+ /* Check if the current slab is not yet allocated. */
if (stack_slabs[slab_index] == NULL) {
+ /* Use the preallocated memory for the current slab. */
stack_slabs[slab_index] = *prealloc;
*prealloc = NULL;
} else {
- /* If this is the last depot slab, do not touch the next one. */
+ /*
+ * Otherwise, use the preallocated memory for the next slab
+ * as long as we do not exceed the maximum number of slabs.
+ */
if (slab_index + 1 < DEPOT_MAX_SLABS) {
stack_slabs[slab_index + 1] = *prealloc;
*prealloc = NULL;
/*
* This smp_store_release pairs with smp_load_acquire()
- * from |next_slab_inited| above and in
- * stack_depot_save().
+ * above and in stack_depot_save().
*/
smp_store_release(&next_slab_inited, 1);
}
}
}
-/* Allocation of a new stack in raw storage */
+/* Allocates a new stack in a stack depot slab. */
static struct stack_record *
depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
{
@@ -253,28 +261,35 @@ 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 slab. */
if (unlikely(slab_offset + required_size > DEPOT_SLAB_SIZE)) {
+ /* Bail out if we reached the slab limit. */
if (unlikely(slab_index + 1 >= DEPOT_MAX_SLABS)) {
WARN_ONCE(1, "Stack depot reached limit capacity");
return NULL;
}
+
+ /* Move on to the next slab. */
slab_index++;
slab_offset = 0;
/*
- * smp_store_release() here pairs with smp_load_acquire() from
- * |next_slab_inited| in stack_depot_save() and
- * depot_init_slab().
+ * smp_store_release() here pairs with smp_load_acquire() in
+ * stack_depot_save() and depot_init_slab().
*/
if (slab_index + 1 < DEPOT_MAX_SLABS)
smp_store_release(&next_slab_inited, 0);
}
+
+ /* Assign the preallocated memory to a slab if required. */
if (*prealloc)
depot_init_slab(prealloc);
+
+ /* Check if we have a slab to save the stack trace. */
if (stack_slabs[slab_index] == NULL)
return NULL;
+ /* Save the stack trace. */
stack = stack_slabs[slab_index] + slab_offset;
-
stack->hash = hash;
stack->size = size;
stack->handle.slab_index = slab_index;
--
2.25.1
