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lib/stackdepot: annotate depot_init_pool and depot_alloc_stack 

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.

Link: https://lkml.kernel.org/r/f80b02951364e6b40deda965b4003de0cd1a532d.1676063693.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Andrey Konovalov 2023-02-10 22:16:01 +01:00 committed by Andrew Morton
parent 514d5c557b
commit cd0fc64e76
1 changed files with 24 additions and 10 deletions
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34
lib/stackdepot.c
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@ -218,32 +218,39 @@ out_unlock:
}
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;