include/linux/dynlocks.h | 33 ++++++++++ lib/Makefile | 4 - lib/dynlocks.c | 152 +++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 187 insertions(+), 2 deletions(-) Index: linux/fs/dcache.c =================================================================== --- linux.orig/fs/dcache.c +++ linux/fs/dcache.c @@ -1678,6 +1678,7 @@ EXPORT_SYMBOL(d_genocide); extern void bdev_cache_init(void); extern void chrdev_init(void); +extern void dynlock_cache_init(void); void __init vfs_caches_init_early(void) { @@ -1707,6 +1708,7 @@ void __init vfs_caches_init(unsigned lon mnt_init(mempages); bdev_cache_init(); chrdev_init(); + dynlock_cache_init(); } EXPORT_SYMBOL(d_alloc); Index: linux/include/linux/dynlocks.h =================================================================== --- linux.orig/include/linux/dynlocks.h +++ linux/include/linux/dynlocks.h @@ -0,0 +1,37 @@ +#ifndef _LINUX_DYNLOCKS_H +#define _LINUX_DYNLOCKS_H + +#include +#include + +#define DYNLOCK_MAGIC 0xd19a10c +#define DYNLOCK_MAGIC2 0xd1956ee + +struct dynlock; +struct dynlock_handle; + +/* + * lock's namespace: + * - list of locks + * - lock to protect this list + */ + +struct dynlock { + unsigned dl_magic; + struct list_head dl_list; + spinlock_t dl_list_lock; +}; + +enum dynlock_type { + DLT_WRITE, + DLT_READ +}; + +void dynlock_init(struct dynlock *dl); +struct dynlock_handle *dynlock_lock(struct dynlock *dl, unsigned long value, + enum dynlock_type lt, int gfp); +void dynlock_unlock(struct dynlock *dl, struct dynlock_handle *lock); + +int dynlock_is_locked(struct dynlock *dl, unsigned long value); +#endif + Index: linux/lib/Makefile =================================================================== --- linux.orig/lib/Makefile +++ linux/lib/Makefile @@ -6,7 +6,7 @@ lib-y := errno.o ctype.o string.o vsprintf.o cmdline.o \ bust_spinlocks.o rbtree.o radix-tree.o dump_stack.o \ kobject.o kref.o idr.o div64.o parser.o int_sqrt.o \ - bitmap.o extable.o + bitmap.o extable.o dynlocks.o obj-y := sort.o Index: linux/lib/dynlocks.c =================================================================== --- linux.orig/lib/dynlocks.c +++ linux/lib/dynlocks.c @@ -0,0 +1,226 @@ +/* + * Dynamic Locks + * + * struct dynlock is lockspace + * one may request lock (exclusive or shared) for some value + * in that lockspace + * + */ + +#include +#include +#include +#include + +static kmem_cache_t * dynlock_cachep = NULL; + +struct dynlock_handle { + unsigned dl_magic; + struct list_head dl_list; + unsigned long dl_value; /* lock value */ + int dl_refcount; /* number of users */ + int dl_readers; + int dl_writers; + int dl_pid; /* holder of the lock */ + wait_queue_head_t dl_wait; +}; + +#define DYNLOCK_LIST_MAGIC 0x11ee91e6 + +void __init dynlock_cache_init(void) +{ + printk(KERN_INFO "init dynlocks cache\n"); + dynlock_cachep = kmem_cache_create("dynlock_cache", + sizeof(struct dynlock_handle), + 0, + SLAB_HWCACHE_ALIGN, + NULL, NULL); + if (dynlock_cachep == NULL) + panic("Can't create dynlock cache"); +} + +/* + * dynlock_init + * + * initialize lockspace + * + */ +void dynlock_init(struct dynlock *dl) +{ + spin_lock_init(&dl->dl_list_lock); + INIT_LIST_HEAD(&dl->dl_list); + dl->dl_magic = DYNLOCK_LIST_MAGIC; +} + +/* + * dynlock_lock + * + * acquires lock (exclusive or shared) in specified lockspace + * each lock in lockspace is allocated separately, so user have + * to specify GFP flags. + * routine returns pointer to lock. this pointer is intended to + * be passed to dynlock_unlock + * + */ +struct dynlock_handle *dynlock_lock(struct dynlock *dl, unsigned long value, + enum dynlock_type lt, int gfp) +{ + struct dynlock_handle *nhl = NULL; + struct dynlock_handle *hl; + + BUG_ON(dl == NULL); + BUG_ON(dl->dl_magic != DYNLOCK_LIST_MAGIC); + +repeat: + /* find requested lock in lockspace */ + spin_lock(&dl->dl_list_lock); + BUG_ON(dl->dl_list.next == NULL); + BUG_ON(dl->dl_list.prev == NULL); + list_for_each_entry(hl, &dl->dl_list, dl_list) { + BUG_ON(hl->dl_list.next == NULL); + BUG_ON(hl->dl_list.prev == NULL); + BUG_ON(hl->dl_magic != DYNLOCK_MAGIC); + if (hl->dl_value == value) { + /* lock is found */ + if (nhl) { + /* someone else just allocated + * lock we didn't find and just created + * so, we drop our lock + */ + kmem_cache_free(dynlock_cachep, nhl); + nhl = NULL; + } + hl->dl_refcount++; + goto found; + } + } + /* lock not found */ + if (nhl) { + /* we already have allocated lock. use it */ + hl = nhl; + nhl = NULL; + list_add(&hl->dl_list, &dl->dl_list); + goto found; + } + spin_unlock(&dl->dl_list_lock); + + /* lock not found and we haven't allocated lock yet. allocate it */ + nhl = kmem_cache_alloc(dynlock_cachep, gfp); + if (nhl == NULL) + return NULL; + nhl->dl_refcount = 1; + nhl->dl_value = value; + nhl->dl_readers = 0; + nhl->dl_writers = 0; + nhl->dl_magic = DYNLOCK_MAGIC; + init_waitqueue_head(&nhl->dl_wait); + + /* while lock is being allocated, someone else may allocate it + * and put onto to list. check this situation + */ + goto repeat; + +found: + if (lt == DLT_WRITE) { + /* exclusive lock: user don't want to share lock at all + * NOTE: one process may take the same lock several times + * this functionaly is useful for rename operations */ + while ((hl->dl_writers && hl->dl_pid != current->pid) || + hl->dl_readers) { + spin_unlock(&dl->dl_list_lock); + wait_event(hl->dl_wait, + hl->dl_writers == 0 && hl->dl_readers == 0); + spin_lock(&dl->dl_list_lock); + } + hl->dl_writers++; + } else { + /* shared lock: user do not want to share lock with writer */ + while (hl->dl_writers) { + spin_unlock(&dl->dl_list_lock); + wait_event(hl->dl_wait, hl->dl_writers == 0); + spin_lock(&dl->dl_list_lock); + } + hl->dl_readers++; + } + hl->dl_pid = current->pid; + spin_unlock(&dl->dl_list_lock); + + return hl; +} + + +/* + * dynlock_unlock + * + * user have to specify lockspace (dl) and pointer to lock structure + * returned by dynlock_lock() + * + */ +void dynlock_unlock(struct dynlock *dl, struct dynlock_handle *hl) +{ + int wakeup = 0; + + BUG_ON(dl == NULL); + BUG_ON(hl == NULL); + BUG_ON(dl->dl_magic != DYNLOCK_LIST_MAGIC); + + if (hl->dl_magic != DYNLOCK_MAGIC) + printk(KERN_EMERG "wrong lock magic: %#x\n", hl->dl_magic); + + BUG_ON(hl->dl_magic != DYNLOCK_MAGIC); + BUG_ON(hl->dl_writers != 0 && current->pid != hl->dl_pid); + + spin_lock(&dl->dl_list_lock); + if (hl->dl_writers) { + BUG_ON(hl->dl_readers != 0); + hl->dl_writers--; + if (hl->dl_writers == 0) + wakeup = 1; + } else if (hl->dl_readers) { + hl->dl_readers--; + if (hl->dl_readers == 0) + wakeup = 1; + } else { + BUG(); + } + if (wakeup) { + hl->dl_pid = 0; + wake_up(&hl->dl_wait); + } + if (--(hl->dl_refcount) == 0) { + hl->dl_magic = DYNLOCK_MAGIC2; + list_del(&hl->dl_list); + kmem_cache_free(dynlock_cachep, hl); + } + spin_unlock(&dl->dl_list_lock); +} + +int dynlock_is_locked(struct dynlock *dl, unsigned long value) +{ + struct dynlock_handle *hl; + int result; + + result = 0; + /* find requested lock in lockspace */ + spin_lock(&dl->dl_list_lock); + BUG_ON(dl->dl_list.next == NULL); + BUG_ON(dl->dl_list.prev == NULL); + list_for_each_entry(hl, &dl->dl_list, dl_list) { + BUG_ON(hl->dl_list.next == NULL); + BUG_ON(hl->dl_list.prev == NULL); + BUG_ON(hl->dl_magic != DYNLOCK_MAGIC); + if (hl->dl_value == value && hl->dl_pid == current->pid) { + /* lock is found */ + result = 1; + break; + } + } + spin_unlock(&dl->dl_list_lock); + return result; +} + +EXPORT_SYMBOL(dynlock_init); +EXPORT_SYMBOL(dynlock_lock); +EXPORT_SYMBOL(dynlock_unlock); +EXPORT_SYMBOL(dynlock_is_locked); +