#ifndef HASH_H #define HASH_H /* Hash table implementation from the GIT project. */ /* Copyright 2008 (C) Linus Torvalds, GPL version 2 */ /* * These are some simple generic hash table helper functions. * Not necessarily suitable for all users, but good for things * where you want to just keep track of a list of things, and * have a good hash to use on them. * * It keeps the hash table at roughly 50-75% free, so the memory * cost of the hash table itself is roughly * * 3 * 2*sizeof(void *) * nr_of_objects * * bytes. * * FIXME: on 64-bit architectures, we waste memory. It would be * good to have just 32-bit pointers, requiring a special allocator * for hashed entries or something. */ #include #define alloc_nr(x) (((x) + 16) * 3 / 2) #define INSERT_HASH_PROTOS(ops, table) \ do { \ void **pos = insert_hash((ops).key, &(ops), &(table)); \ /* We already had an entry there? */ \ if (pos) { \ (ops).next = *pos; \ *pos = &(ops); \ } \ } while (0) struct hash_table_entry { unsigned int hash; void *ptr; }; struct hash_table { unsigned int size, nr; struct hash_table_entry *array; }; extern void *lookup_hash(unsigned int hash, const struct hash_table *table); extern void **insert_hash(unsigned int hash, void *ptr, struct hash_table *table); extern void *remove_hash(unsigned int hash, void *ptr, void *ptr_next, struct hash_table *table); extern int for_each_hash(const struct hash_table *table, int (*fn)(void *)); extern int for_each_hash_int(const struct hash_table *table, int (*fn)(void *, int), int arg); extern void free_hash(struct hash_table *table); static inline void init_hash(struct hash_table *table) { table->size = 0; table->nr = 0; table->array = NULL; } static inline unsigned char icase_hash(unsigned char c) { return c & ~((c & 0x40) >> 1); } static inline unsigned int hash_name(const char *name, int namelen) { unsigned int hash = 0x123; do { unsigned char c = *name++; c = icase_hash(c); hash = hash * 101 + c; } while (--namelen); return hash; } #endif /* HASH_H */ bff09a6ff164aec2b33bf1f9a488c45ac108413'>commitdiff
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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2016-06-15 16:08:17 -0700
committerIngo Molnar <mingo@kernel.org>2016-06-17 09:54:45 +0200
commitebff09a6ff164aec2b33bf1f9a488c45ac108413 (patch)
tree4c2e43caeacbd254daa8439564e991b1de82750c /Documentation/i2c
parentb316ff783d17bd6217804e2e4385ce9347d7dad9 (diff)
locking/Documentation: Clarify limited control-dependency scope
Nothing in the control-dependencies section of memory-barriers.txt says that control dependencies don't extend beyond the end of the if-statement containing the control dependency. Worse yet, in many situations, they do extend beyond that if-statement. In particular, the compiler cannot destroy the control dependency given proper use of READ_ONCE() and WRITE_ONCE(). However, a weakly ordered system having a conditional-move instruction provides the control-dependency guarantee only to code within the scope of the if-statement itself. This commit therefore adds words and an example demonstrating this limitation of control dependencies. Reported-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: corbet@lwn.net Cc: linux-arch@vger.kernel.org Cc: linux-doc@vger.kernel.org Link: http://lkml.kernel.org/r/20160615230817.GA18039@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/i2c')