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-rw-r--r--include/linux/genalloc.h34
1 files changed, 28 insertions, 6 deletions
diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h
index 5bbebda78b0..5e98eeb2af3 100644
--- a/include/linux/genalloc.h
+++ b/include/linux/genalloc.h
@@ -1,8 +1,26 @@
/*
- * Basic general purpose allocator for managing special purpose memory
- * not managed by the regular kmalloc/kfree interface.
- * Uses for this includes on-device special memory, uncached memory
- * etc.
+ * Basic general purpose allocator for managing special purpose
+ * memory, for example, memory that is not managed by the regular
+ * kmalloc/kfree interface. Uses for this includes on-device special
+ * memory, uncached memory etc.
+ *
+ * It is safe to use the allocator in NMI handlers and other special
+ * unblockable contexts that could otherwise deadlock on locks. This
+ * is implemented by using atomic operations and retries on any
+ * conflicts. The disadvantage is that there may be livelocks in
+ * extreme cases. For better scalability, one allocator can be used
+ * for each CPU.
+ *
+ * The lockless operation only works if there is enough memory
+ * available. If new memory is added to the pool a lock has to be
+ * still taken. So any user relying on locklessness has to ensure
+ * that sufficient memory is preallocated.
+ *
+ * The basic atomic operation of this allocator is cmpxchg on long.
+ * On architectures that don't have NMI-safe cmpxchg implementation,
+ * the allocator can NOT be used in NMI handler. So code uses the
+ * allocator in NMI handler should depend on
+ * CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
*
* This source code is licensed under the GNU General Public License,
* Version 2. See the file COPYING for more details.
@@ -15,7 +33,7 @@
* General purpose special memory pool descriptor.
*/
struct gen_pool {
- rwlock_t lock;
+ spinlock_t lock;
struct list_head chunks; /* list of chunks in this pool */
int min_alloc_order; /* minimum allocation order */
};
@@ -24,8 +42,8 @@ struct gen_pool {
* General purpose special memory pool chunk descriptor.
*/
struct gen_pool_chunk {
- spinlock_t lock;
struct list_head next_chunk; /* next chunk in pool */
+ atomic_t avail;
phys_addr_t phys_addr; /* physical starting address of memory chunk */
unsigned long start_addr; /* starting address of memory chunk */
unsigned long end_addr; /* ending address of memory chunk */
@@ -56,4 +74,8 @@ static inline int gen_pool_add(struct gen_pool *pool, unsigned long addr,
extern void gen_pool_destroy(struct gen_pool *);
extern unsigned long gen_pool_alloc(struct gen_pool *, size_t);
extern void gen_pool_free(struct gen_pool *, unsigned long, size_t);
+extern void gen_pool_for_each_chunk(struct gen_pool *,
+ void (*)(struct gen_pool *, struct gen_pool_chunk *, void *), void *);
+extern size_t gen_pool_avail(struct gen_pool *);
+extern size_t gen_pool_size(struct gen_pool *);
#endif /* __GENALLOC_H__ */