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lib/stackdepot: rework helpers for depot_alloc_stack

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Split code in depot_alloc_stack and depot_init_pool into 3 functions:

1. depot_keep_next_pool that keeps preallocated memory for the next pool
   if required.

2. depot_update_pools that moves on to the next pool if there's no space
   left in the current pool, uses preallocated memory for the new current
   pool if required, and calls depot_keep_next_pool otherwise.

3. depot_alloc_stack that calls depot_update_pools and then allocates
   a stack record as before.

This makes it somewhat easier to follow the logic of depot_alloc_stack and
also serves as a preparation for implementing the eviction of stack
records from the stack depot.

Link: https://lkml.kernel.org/r/71fb144d42b701fcb46708d7f4be6801a4a8270e.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Andrey Konovalov 2023-11-20 18:47:06 +01:00 committed by Andrew Morton
parent fcccc41ecb
commit 94b7d32870
1 changed files with 49 additions and 37 deletions
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86
lib/stackdepot.c
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@ -225,11 +225,11 @@ 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)
/* Keeps the preallocated memory to be used for the next stack depot pool. */
static void depot_keep_next_pool(void **prealloc)
{
/*
* If the next pool is already initialized or the maximum number of
* If the next pool is already saved or the maximum number of
* pools is reached, do not use the preallocated memory.
* Access next_pool_required non-atomically, as there are no concurrent
* write accesses to this variable.
@ -237,44 +237,34 @@ static void depot_init_pool(void **prealloc)
if (!next_pool_required)
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;
/*
* 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;
} else {
/*
* 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;
}
/*
* At this point, either the next pool is initialized or the
* maximum number of pools is reached. In either case, take
* note that initializing another pool is not required.
* smp_store_release() pairs with smp_load_acquire() in
* stack_depot_save().
*/
smp_store_release(&next_pool_required, 0);
}
/*
* At this point, either the next pool is kept or the maximum
* number of pools is reached. In either case, take note that
* keeping another pool is not required.
* smp_store_release() pairs with smp_load_acquire() in
* stack_depot_save().
*/
smp_store_release(&next_pool_required, 0);
}
/* 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)
/* Updates references to the current and the next stack depot pools. */
static bool depot_update_pools(size_t required_size, void **prealloc)
{
struct stack_record *stack;
size_t required_size = DEPOT_STACK_RECORD_SIZE;
/* 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;
return false;
}
/*
@ -284,9 +274,10 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
*/
WRITE_ONCE(pool_index, pool_index + 1);
pool_offset = 0;
/*
* If the maximum number of pools is not reached, take note
* that the next pool needs to initialized.
* that the next pool needs to be initialized.
* smp_store_release() pairs with smp_load_acquire() in
* stack_depot_save().
*/
@ -294,9 +285,30 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
smp_store_release(&next_pool_required, 1);
}
/* Assign the preallocated memory to a pool if required. */
/* Check if the current pool is not yet allocated. */
if (*prealloc && stack_pools[pool_index] == NULL) {
/* Use the preallocated memory for the current pool. */
stack_pools[pool_index] = *prealloc;
*prealloc = NULL;
return true;
}
/* Otherwise, try using the preallocated memory for the next pool. */
if (*prealloc)
depot_init_pool(prealloc);
depot_keep_next_pool(prealloc);
return true;
}
/* 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)
{
struct stack_record *stack;
size_t required_size = DEPOT_STACK_RECORD_SIZE;
/* Update current and next pools if required and possible. */
if (!depot_update_pools(required_size, prealloc))
return NULL;
/* Check if we have a pool to save the stack trace. */
if (stack_pools[pool_index] == NULL)
@ -330,7 +342,7 @@ static struct stack_record *depot_fetch_stack(depot_stack_handle_t handle)
union handle_parts parts = { .handle = handle };
/*
* READ_ONCE() pairs with potential concurrent write in
* depot_alloc_stack().
* depot_update_pools().
*/
int pool_index_cached = READ_ONCE(pool_index);
void *pool;
@ -430,7 +442,7 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
* the memory now - we won't be able to do that under the lock.
*
* smp_load_acquire() pairs with smp_store_release() in
* depot_alloc_stack() and depot_init_pool().
* depot_update_pools() and depot_keep_next_pool().
*/
if (unlikely(can_alloc && smp_load_acquire(&next_pool_required))) {
/*
@ -467,7 +479,7 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
* Stack depot already contains this stack trace, but let's
* keep the preallocated memory for the future.
*/
depot_init_pool(&prealloc);
depot_keep_next_pool(&prealloc);
}
raw_spin_unlock_irqrestore(&pool_lock, flags);