diff options
Diffstat (limited to 'kernel/futex.c')
| -rw-r--r-- | kernel/futex.c | 38 |
1 files changed, 34 insertions, 4 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index 33664f70e2d2..2c4be467fecd 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -179,7 +179,15 @@ int __read_mostly futex_cmpxchg_enabled; * Futex flags used to encode options to functions and preserve them across * restarts. */ -#define FLAGS_SHARED 0x01 +#ifdef CONFIG_MMU +# define FLAGS_SHARED 0x01 +#else +/* + * NOMMU does not have per process address space. Let the compiler optimize + * code away. + */ +# define FLAGS_SHARED 0x00 +#endif #define FLAGS_CLOCKRT 0x02 #define FLAGS_HAS_TIMEOUT 0x04 @@ -373,8 +381,12 @@ static inline int hb_waiters_pending(struct futex_hash_bucket *hb) #endif } -/* - * We hash on the keys returned from get_futex_key (see below). +/** + * hash_futex - Return the hash bucket in the global hash + * @key: Pointer to the futex key for which the hash is calculated + * + * We hash on the keys returned from get_futex_key (see below) and return the + * corresponding hash bucket in the global hash. */ static struct futex_hash_bucket *hash_futex(union futex_key *key) { @@ -384,7 +396,12 @@ static struct futex_hash_bucket *hash_futex(union futex_key *key) return &futex_queues[hash & (futex_hashsize - 1)]; } -/* + +/** + * match_futex - Check whether two futex keys are equal + * @key1: Pointer to key1 + * @key2: Pointer to key2 + * * Return 1 if two futex_keys are equal, 0 otherwise. */ static inline int match_futex(union futex_key *key1, union futex_key *key2) @@ -405,6 +422,16 @@ static void get_futex_key_refs(union futex_key *key) if (!key->both.ptr) return; + /* + * On MMU less systems futexes are always "private" as there is no per + * process address space. We need the smp wmb nevertheless - yes, + * arch/blackfin has MMU less SMP ... + */ + if (!IS_ENABLED(CONFIG_MMU)) { + smp_mb(); /* explicit smp_mb(); (B) */ + return; + } + switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { case FUT_OFF_INODE: ihold(key->shared.inode); /* implies smp_mb(); (B) */ @@ -436,6 +463,9 @@ static void drop_futex_key_refs(union futex_key *key) return; } + if (!IS_ENABLED(CONFIG_MMU)) + return; + switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { case FUT_OFF_INODE: iput(key->shared.inode); |