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Commit 92f36cca authored by Tom Herbert's avatar Tom Herbert Committed by David S. Miller
Browse files

spinlock: Add library function to allocate spinlock buckets array 



Add two new library functions: alloc_bucket_spinlocks and
free_bucket_spinlocks. These are used to allocate and free an array
of spinlocks that are useful as locks for hash buckets. The interface
specifies the maximum number of spinlocks in the array as well
as a CPU multiplier to derive the number of spinlocks to allocate.
The number allocated is rounded up to a power of two to make the
array amenable to hash lookup.

Signed-off-by: default avatarTom Herbert <tom@quantonium.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2b860931

include/linux/spinlock.h

+6 −0
Original line number Diff line number Diff line
@@ -414,4 +414,10 @@ extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock); 
#define atomic_dec_and_lock(atomic, lock) \

		__cond_lock(lock, _atomic_dec_and_lock(atomic, lock))



int alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,

			   size_t max_size, unsigned int cpu_mult,

			   gfp_t gfp);



void free_bucket_spinlocks(spinlock_t *locks);



#endif /* __LINUX_SPINLOCK_H */

lib/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -39,7 +39,7 @@ obj-y += bcd.o div64.o sort.o parser.o debug_locks.o random32.o \ 
	 gcd.o lcm.o list_sort.o uuid.o flex_array.o iov_iter.o clz_ctz.o \

	 bsearch.o find_bit.o llist.o memweight.o kfifo.o \

	 percpu-refcount.o percpu_ida.o rhashtable.o reciprocal_div.o \

	 once.o refcount.o usercopy.o errseq.o

	 once.o refcount.o usercopy.o errseq.o bucket_locks.o

obj-$(CONFIG_STRING_SELFTEST) += test_string.o

obj-y += string_helpers.o

obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o

lib/bucket_locks.c

0 → 100644
+54 −0
Original line number Diff line number Diff line 
#include <linux/export.h>

#include <linux/kernel.h>

#include <linux/mm.h>

#include <linux/slab.h>

#include <linux/vmalloc.h>



/* Allocate an array of spinlocks to be accessed by a hash. Two arguments

 * indicate the number of elements to allocate in the array. max_size

 * gives the maximum number of elements to allocate. cpu_mult gives

 * the number of locks per CPU to allocate. The size is rounded up

 * to a power of 2 to be suitable as a hash table.

 */



int alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *locks_mask,

			   size_t max_size, unsigned int cpu_mult, gfp_t gfp)

{

	spinlock_t *tlocks = NULL;

	unsigned int i, size;

#if defined(CONFIG_PROVE_LOCKING)

	unsigned int nr_pcpus = 2;

#else

	unsigned int nr_pcpus = num_possible_cpus();

#endif



	if (cpu_mult) {

		nr_pcpus = min_t(unsigned int, nr_pcpus, 64UL);

		size = min_t(unsigned int, nr_pcpus * cpu_mult, max_size);

	} else {

		size = max_size;

	}



	if (sizeof(spinlock_t) != 0) {

		if (gfpflags_allow_blocking(gfp))

			tlocks = kvmalloc(size * sizeof(spinlock_t), gfp);

		else

			tlocks = kmalloc_array(size, sizeof(spinlock_t), gfp);

		if (!tlocks)

			return -ENOMEM;

		for (i = 0; i < size; i++)

			spin_lock_init(&tlocks[i]);

	}



	*locks = tlocks;

	*locks_mask = size - 1;



	return 0;

}

EXPORT_SYMBOL(alloc_bucket_spinlocks);



void free_bucket_spinlocks(spinlock_t *locks)

{

	kvfree(locks);

}

EXPORT_SYMBOL(free_bucket_spinlocks);