diff options
Diffstat (limited to 'include/linux/stackdepot.h')
| -rw-r--r-- | include/linux/stackdepot.h | 118 |
1 files changed, 104 insertions, 14 deletions
diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index e58306783d8e..e9ec32fb97d4 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -11,8 +11,6 @@ * SLUB_DEBUG needs 256 bytes per object for that). Since allocation and free * stack traces often repeat, using stack depot allows to save about 100x space. * - * Stack traces are never removed from the stack depot. - * * Author: Alexander Potapenko <glider@google.com> * Copyright (C) 2016 Google, Inc. * @@ -32,6 +30,64 @@ typedef u32 depot_stack_handle_t; */ #define STACK_DEPOT_EXTRA_BITS 5 +#define DEPOT_HANDLE_BITS (sizeof(depot_stack_handle_t) * 8) + +#define DEPOT_POOL_ORDER 2 /* Pool size order, 4 pages */ +#define DEPOT_POOL_SIZE (1LL << (PAGE_SHIFT + DEPOT_POOL_ORDER)) +#define DEPOT_STACK_ALIGN 4 +#define DEPOT_OFFSET_BITS (DEPOT_POOL_ORDER + PAGE_SHIFT - DEPOT_STACK_ALIGN) +#define DEPOT_POOL_INDEX_BITS (DEPOT_HANDLE_BITS - DEPOT_OFFSET_BITS - \ + STACK_DEPOT_EXTRA_BITS) + +#ifdef CONFIG_STACKDEPOT +/* Compact structure that stores a reference to a stack. */ +union handle_parts { + depot_stack_handle_t handle; + struct { + u32 pool_index_plus_1 : DEPOT_POOL_INDEX_BITS; + u32 offset : DEPOT_OFFSET_BITS; + u32 extra : STACK_DEPOT_EXTRA_BITS; + }; +}; + +struct stack_record { + struct list_head hash_list; /* Links in the hash table */ + u32 hash; /* Hash in hash table */ + u32 size; /* Number of stored frames */ + union handle_parts handle; /* Constant after initialization */ + refcount_t count; + union { + unsigned long entries[CONFIG_STACKDEPOT_MAX_FRAMES]; /* Frames */ + struct { + /* + * An important invariant of the implementation is to + * only place a stack record onto the freelist iff its + * refcount is zero. Because stack records with a zero + * refcount are never considered as valid, it is safe to + * union @entries and freelist management state below. + * Conversely, as soon as an entry is off the freelist + * and its refcount becomes non-zero, the below must not + * be accessed until being placed back on the freelist. + */ + struct list_head free_list; /* Links in the freelist */ + unsigned long rcu_state; /* RCU cookie */ + }; + }; +}; +#endif + +typedef u32 depot_flags_t; + +/* + * Flags that can be passed to stack_depot_save_flags(); see the comment next + * to its declaration for more details. + */ +#define STACK_DEPOT_FLAG_CAN_ALLOC ((depot_flags_t)0x0001) +#define STACK_DEPOT_FLAG_GET ((depot_flags_t)0x0002) + +#define STACK_DEPOT_FLAGS_NUM 2 +#define STACK_DEPOT_FLAGS_MASK ((depot_flags_t)((1 << STACK_DEPOT_FLAGS_NUM) - 1)) + /* * Using stack depot requires its initialization, which can be done in 3 ways: * @@ -69,31 +125,39 @@ static inline int stack_depot_early_init(void) { return 0; } #endif /** - * __stack_depot_save - Save a stack trace to stack depot + * stack_depot_save_flags - Save a stack trace to stack depot * * @entries: Pointer to the stack trace * @nr_entries: Number of frames in the stack * @alloc_flags: Allocation GFP flags - * @can_alloc: Allocate stack pools (increased chance of failure if false) + * @depot_flags: Stack depot flags + * + * Saves a stack trace from @entries array of size @nr_entries. + * + * If STACK_DEPOT_FLAG_CAN_ALLOC is set in @depot_flags, stack depot can + * replenish the stack pools in case no space is left (allocates using GFP + * flags of @alloc_flags). Otherwise, stack depot avoids any allocations and + * fails if no space is left to store the stack trace. * - * Saves a stack trace from @entries array of size @nr_entries. If @can_alloc is - * %true, stack depot can replenish the stack pools in case no space is left - * (allocates using GFP flags of @alloc_flags). If @can_alloc is %false, avoids - * any allocations and fails if no space is left to store the stack trace. + * If STACK_DEPOT_FLAG_GET is set in @depot_flags, stack depot will increment + * the refcount on the saved stack trace if it already exists in stack depot. + * Users of this flag must also call stack_depot_put() when keeping the stack + * trace is no longer required to avoid overflowing the refcount. * * If the provided stack trace comes from the interrupt context, only the part * up to the interrupt entry is saved. * - * Context: Any context, but setting @can_alloc to %false is required if + * Context: Any context, but setting STACK_DEPOT_FLAG_CAN_ALLOC is required if * alloc_pages() cannot be used from the current context. Currently * this is the case for contexts where neither %GFP_ATOMIC nor * %GFP_NOWAIT can be used (NMI, raw_spin_lock). * * Return: Handle of the stack struct stored in depot, 0 on failure */ -depot_stack_handle_t __stack_depot_save(unsigned long *entries, - unsigned int nr_entries, - gfp_t gfp_flags, bool can_alloc); +depot_stack_handle_t stack_depot_save_flags(unsigned long *entries, + unsigned int nr_entries, + gfp_t gfp_flags, + depot_flags_t depot_flags); /** * stack_depot_save - Save a stack trace to stack depot @@ -102,8 +166,11 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries, * @nr_entries: Number of frames in the stack * @alloc_flags: Allocation GFP flags * - * Context: Contexts where allocations via alloc_pages() are allowed. - * See __stack_depot_save() for more details. + * Does not increment the refcount on the saved stack trace; see + * stack_depot_save_flags() for more details. + * + * Context: Contexts where allocations via alloc_pages() are allowed; + * see stack_depot_save_flags() for more details. * * Return: Handle of the stack trace stored in depot, 0 on failure */ @@ -111,6 +178,17 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries, unsigned int nr_entries, gfp_t gfp_flags); /** + * __stack_depot_get_stack_record - Get a pointer to a stack_record struct + * + * @handle: Stack depot handle + * + * This function is only for internal purposes. + * + * Return: Returns a pointer to a stack_record struct + */ +struct stack_record *__stack_depot_get_stack_record(depot_stack_handle_t handle); + +/** * stack_depot_fetch - Fetch a stack trace from stack depot * * @handle: Stack depot handle returned from stack_depot_save() @@ -142,6 +220,18 @@ int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size, int spaces); /** + * stack_depot_put - Drop a reference to a stack trace from stack depot + * + * @handle: Stack depot handle returned from stack_depot_save() + * + * The stack trace is evicted from stack depot once all references to it have + * been dropped (once the number of stack_depot_evict() calls matches the + * number of stack_depot_save_flags() calls with STACK_DEPOT_FLAG_GET set for + * this stack trace). + */ +void stack_depot_put(depot_stack_handle_t handle); + +/** * stack_depot_set_extra_bits - Set extra bits in a stack depot handle * * @handle: Stack depot handle returned from stack_depot_save() |