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-rw-r--r--lib/genalloc.c300
1 files changed, 243 insertions, 57 deletions
diff --git a/lib/genalloc.c b/lib/genalloc.c
index 577ddf80597..f352cc42f4f 100644
--- a/lib/genalloc.c
+++ b/lib/genalloc.c
@@ -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.
*
* Copyright 2005 (C) Jes Sorensen <jes@trained-monkey.org>
*
@@ -13,8 +31,109 @@
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/bitmap.h>
+#include <linux/rculist.h>
+#include <linux/interrupt.h>
#include <linux/genalloc.h>
+static int set_bits_ll(unsigned long *addr, unsigned long mask_to_set)
+{
+ unsigned long val, nval;
+
+ nval = *addr;
+ do {
+ val = nval;
+ if (val & mask_to_set)
+ return -EBUSY;
+ cpu_relax();
+ } while ((nval = cmpxchg(addr, val, val | mask_to_set)) != val);
+
+ return 0;
+}
+
+static int clear_bits_ll(unsigned long *addr, unsigned long mask_to_clear)
+{
+ unsigned long val, nval;
+
+ nval = *addr;
+ do {
+ val = nval;
+ if ((val & mask_to_clear) != mask_to_clear)
+ return -EBUSY;
+ cpu_relax();
+ } while ((nval = cmpxchg(addr, val, val & ~mask_to_clear)) != val);
+
+ return 0;
+}
+
+/*
+ * bitmap_set_ll - set the specified number of bits at the specified position
+ * @map: pointer to a bitmap
+ * @start: a bit position in @map
+ * @nr: number of bits to set
+ *
+ * Set @nr bits start from @start in @map lock-lessly. Several users
+ * can set/clear the same bitmap simultaneously without lock. If two
+ * users set the same bit, one user will return remain bits, otherwise
+ * return 0.
+ */
+static int bitmap_set_ll(unsigned long *map, int start, int nr)
+{
+ unsigned long *p = map + BIT_WORD(start);
+ const int size = start + nr;
+ int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
+ unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
+
+ while (nr - bits_to_set >= 0) {
+ if (set_bits_ll(p, mask_to_set))
+ return nr;
+ nr -= bits_to_set;
+ bits_to_set = BITS_PER_LONG;
+ mask_to_set = ~0UL;
+ p++;
+ }
+ if (nr) {
+ mask_to_set &= BITMAP_LAST_WORD_MASK(size);
+ if (set_bits_ll(p, mask_to_set))
+ return nr;
+ }
+
+ return 0;
+}
+
+/*
+ * bitmap_clear_ll - clear the specified number of bits at the specified position
+ * @map: pointer to a bitmap
+ * @start: a bit position in @map
+ * @nr: number of bits to set
+ *
+ * Clear @nr bits start from @start in @map lock-lessly. Several users
+ * can set/clear the same bitmap simultaneously without lock. If two
+ * users clear the same bit, one user will return remain bits,
+ * otherwise return 0.
+ */
+static int bitmap_clear_ll(unsigned long *map, int start, int nr)
+{
+ unsigned long *p = map + BIT_WORD(start);
+ const int size = start + nr;
+ int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
+ unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
+
+ while (nr - bits_to_clear >= 0) {
+ if (clear_bits_ll(p, mask_to_clear))
+ return nr;
+ nr -= bits_to_clear;
+ bits_to_clear = BITS_PER_LONG;
+ mask_to_clear = ~0UL;
+ p++;
+ }
+ if (nr) {
+ mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
+ if (clear_bits_ll(p, mask_to_clear))
+ return nr;
+ }
+
+ return 0;
+}
/**
* gen_pool_create - create a new special memory pool
@@ -30,7 +149,7 @@ struct gen_pool *gen_pool_create(int min_alloc_order, int nid)
pool = kmalloc_node(sizeof(struct gen_pool), GFP_KERNEL, nid);
if (pool != NULL) {
- rwlock_init(&pool->lock);
+ spin_lock_init(&pool->lock);
INIT_LIST_HEAD(&pool->chunks);
pool->min_alloc_order = min_alloc_order;
}
@@ -63,14 +182,14 @@ int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phy
if (unlikely(chunk == NULL))
return -ENOMEM;
- spin_lock_init(&chunk->lock);
chunk->phys_addr = phys;
chunk->start_addr = virt;
chunk->end_addr = virt + size;
+ atomic_set(&chunk->avail, size);
- write_lock(&pool->lock);
- list_add(&chunk->next_chunk, &pool->chunks);
- write_unlock(&pool->lock);
+ spin_lock(&pool->lock);
+ list_add_rcu(&chunk->next_chunk, &pool->chunks);
+ spin_unlock(&pool->lock);
return 0;
}
@@ -85,19 +204,19 @@ EXPORT_SYMBOL(gen_pool_add_virt);
*/
phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long addr)
{
- struct list_head *_chunk;
struct gen_pool_chunk *chunk;
+ phys_addr_t paddr = -1;
- read_lock(&pool->lock);
- list_for_each(_chunk, &pool->chunks) {
- chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
-
- if (addr >= chunk->start_addr && addr < chunk->end_addr)
- return chunk->phys_addr + addr - chunk->start_addr;
+ rcu_read_lock();
+ list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
+ if (addr >= chunk->start_addr && addr < chunk->end_addr) {
+ paddr = chunk->phys_addr + (addr - chunk->start_addr);
+ break;
+ }
}
- read_unlock(&pool->lock);
+ rcu_read_unlock();
- return -1;
+ return paddr;
}
EXPORT_SYMBOL(gen_pool_virt_to_phys);
@@ -115,7 +234,6 @@ void gen_pool_destroy(struct gen_pool *pool)
int order = pool->min_alloc_order;
int bit, end_bit;
-
list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
list_del(&chunk->next_chunk);
@@ -137,44 +255,50 @@ EXPORT_SYMBOL(gen_pool_destroy);
* @size: number of bytes to allocate from the pool
*
* Allocate the requested number of bytes from the specified pool.
- * Uses a first-fit algorithm.
+ * Uses a first-fit algorithm. Can not be used in NMI handler on
+ * architectures without NMI-safe cmpxchg implementation.
*/
unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
{
- struct list_head *_chunk;
struct gen_pool_chunk *chunk;
- unsigned long addr, flags;
+ unsigned long addr = 0;
int order = pool->min_alloc_order;
- int nbits, start_bit, end_bit;
+ int nbits, start_bit = 0, end_bit, remain;
+
+#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
+ BUG_ON(in_nmi());
+#endif
if (size == 0)
return 0;
nbits = (size + (1UL << order) - 1) >> order;
-
- read_lock(&pool->lock);
- list_for_each(_chunk, &pool->chunks) {
- chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
+ rcu_read_lock();
+ list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
+ if (size > atomic_read(&chunk->avail))
+ continue;
end_bit = (chunk->end_addr - chunk->start_addr) >> order;
-
- spin_lock_irqsave(&chunk->lock, flags);
- start_bit = bitmap_find_next_zero_area(chunk->bits, end_bit, 0,
- nbits, 0);
- if (start_bit >= end_bit) {
- spin_unlock_irqrestore(&chunk->lock, flags);
+retry:
+ start_bit = bitmap_find_next_zero_area(chunk->bits, end_bit,
+ start_bit, nbits, 0);
+ if (start_bit >= end_bit)
continue;
+ remain = bitmap_set_ll(chunk->bits, start_bit, nbits);
+ if (remain) {
+ remain = bitmap_clear_ll(chunk->bits, start_bit,
+ nbits - remain);
+ BUG_ON(remain);
+ goto retry;
}
addr = chunk->start_addr + ((unsigned long)start_bit << order);
-
- bitmap_set(chunk->bits, start_bit, nbits);
- spin_unlock_irqrestore(&chunk->lock, flags);
- read_unlock(&pool->lock);
- return addr;
+ size = nbits << order;
+ atomic_sub(size, &chunk->avail);
+ break;
}
- read_unlock(&pool->lock);
- return 0;
+ rcu_read_unlock();
+ return addr;
}
EXPORT_SYMBOL(gen_pool_alloc);
@@ -184,33 +308,95 @@ EXPORT_SYMBOL(gen_pool_alloc);
* @addr: starting address of memory to free back to pool
* @size: size in bytes of memory to free
*
- * Free previously allocated special memory back to the specified pool.
+ * Free previously allocated special memory back to the specified
+ * pool. Can not be used in NMI handler on architectures without
+ * NMI-safe cmpxchg implementation.
*/
void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
{
- struct list_head *_chunk;
struct gen_pool_chunk *chunk;
- unsigned long flags;
int order = pool->min_alloc_order;
- int bit, nbits;
+ int start_bit, nbits, remain;
- nbits = (size + (1UL << order) - 1) >> order;
-
- read_lock(&pool->lock);
- list_for_each(_chunk, &pool->chunks) {
- chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
+#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
+ BUG_ON(in_nmi());
+#endif
+ nbits = (size + (1UL << order) - 1) >> order;
+ rcu_read_lock();
+ list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
if (addr >= chunk->start_addr && addr < chunk->end_addr) {
BUG_ON(addr + size > chunk->end_addr);
- spin_lock_irqsave(&chunk->lock, flags);
- bit = (addr - chunk->start_addr) >> order;
- while (nbits--)
- __clear_bit(bit++, chunk->bits);
- spin_unlock_irqrestore(&chunk->lock, flags);
- break;
+ start_bit = (addr - chunk->start_addr) >> order;
+ remain = bitmap_clear_ll(chunk->bits, start_bit, nbits);
+ BUG_ON(remain);
+ size = nbits << order;
+ atomic_add(size, &chunk->avail);
+ rcu_read_unlock();
+ return;
}
}
- BUG_ON(nbits > 0);
- read_unlock(&pool->lock);
+ rcu_read_unlock();
+ BUG();
}
EXPORT_SYMBOL(gen_pool_free);
+
+/**
+ * gen_pool_for_each_chunk - call func for every chunk of generic memory pool
+ * @pool: the generic memory pool
+ * @func: func to call
+ * @data: additional data used by @func
+ *
+ * Call @func for every chunk of generic memory pool. The @func is
+ * called with rcu_read_lock held.
+ */
+void gen_pool_for_each_chunk(struct gen_pool *pool,
+ void (*func)(struct gen_pool *pool, struct gen_pool_chunk *chunk, void *data),
+ void *data)
+{
+ struct gen_pool_chunk *chunk;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(chunk, &(pool)->chunks, next_chunk)
+ func(pool, chunk, data);
+ rcu_read_unlock();
+}
+EXPORT_SYMBOL(gen_pool_for_each_chunk);
+
+/**
+ * gen_pool_avail - get available free space of the pool
+ * @pool: pool to get available free space
+ *
+ * Return available free space of the specified pool.
+ */
+size_t gen_pool_avail(struct gen_pool *pool)
+{
+ struct gen_pool_chunk *chunk;
+ size_t avail = 0;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
+ avail += atomic_read(&chunk->avail);
+ rcu_read_unlock();
+ return avail;
+}
+EXPORT_SYMBOL_GPL(gen_pool_avail);
+
+/**
+ * gen_pool_size - get size in bytes of memory managed by the pool
+ * @pool: pool to get size
+ *
+ * Return size in bytes of memory managed by the pool.
+ */
+size_t gen_pool_size(struct gen_pool *pool)
+{
+ struct gen_pool_chunk *chunk;
+ size_t size = 0;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
+ size += chunk->end_addr - chunk->start_addr;
+ rcu_read_unlock();
+ return size;
+}
+EXPORT_SYMBOL_GPL(gen_pool_size);