diff options
| author | Kent Overstreet <kent.overstreet@gmail.com> | 2021-04-26 19:40:09 -0400 |
|---|---|---|
| committer | Kent Overstreet <kent.overstreet@gmail.com> | 2021-04-26 20:18:47 -0400 |
| commit | a14d39d7ac45eebe45ed0772d1ed837f15b15af4 (patch) | |
| tree | e05a03cfe138fde9f0bceae21f244aaf00c5d9f5 | |
| parent | edc3ffe8f25506e60218aa6eb5cbcd3a019f6210 (diff) | |
bit_spinlocks now use futexes
Spinlocks aren't a good idea in userspace, where we can't actually
disable preemption.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
| -rw-r--r-- | include/linux/bit_spinlock.h | 44 | ||||
| -rw-r--r-- | include/linux/rhashtable.h | 1 |
2 files changed, 24 insertions, 21 deletions
diff --git a/include/linux/bit_spinlock.h b/include/linux/bit_spinlock.h index 0e88820a..ed47cc63 100644 --- a/include/linux/bit_spinlock.h +++ b/include/linux/bit_spinlock.h @@ -3,38 +3,40 @@ #include <linux/kernel.h> #include <linux/preempt.h> -#include <linux/atomic.h> -#include <linux/bug.h> +#include <linux/futex.h> -static inline void bit_spin_lock(int bitnum, unsigned long *addr) +static inline void bit_spin_lock(int nr, unsigned long *_addr) { - while (unlikely(test_and_set_bit_lock(bitnum, addr))) { - do { - cpu_relax(); - } while (test_bit(bitnum, addr)); - } -} + u32 mask, *addr = ((u32 *) _addr) + (nr / 32), v; -static inline int bit_spin_trylock(int bitnum, unsigned long *addr) -{ - return !test_and_set_bit_lock(bitnum, addr); -} + nr &= 31; + mask = 1U << nr; -static inline void bit_spin_unlock(int bitnum, unsigned long *addr) -{ - BUG_ON(!test_bit(bitnum, addr)); + while (1) { + v = __atomic_fetch_or(addr, mask, __ATOMIC_ACQUIRE); + if (!(v & mask)) + break; - clear_bit_unlock(bitnum, addr); + futex(addr, FUTEX_WAIT|FUTEX_PRIVATE_FLAG, v, NULL, NULL, 0); + } } -static inline void __bit_spin_unlock(int bitnum, unsigned long *addr) +static inline void bit_spin_wake(int nr, unsigned long *_addr) { - bit_spin_unlock(bitnum, addr); + u32 *addr = ((u32 *) _addr) + (nr / 32); + + futex(addr, FUTEX_WAKE|FUTEX_PRIVATE_FLAG, INT_MAX, NULL, NULL, 0); } -static inline int bit_spin_is_locked(int bitnum, unsigned long *addr) +static inline void bit_spin_unlock(int nr, unsigned long *_addr) { - return test_bit(bitnum, addr); + u32 mask, *addr = ((u32 *) _addr) + (nr / 32); + + nr &= 31; + mask = 1U << nr; + + __atomic_and_fetch(addr, ~mask, __ATOMIC_RELEASE); + futex(addr, FUTEX_WAKE|FUTEX_PRIVATE_FLAG, INT_MAX, NULL, NULL, 0); } #endif /* __LINUX_BIT_SPINLOCK_H */ diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h index 6cf8c257..c5e717bf 100644 --- a/include/linux/rhashtable.h +++ b/include/linux/rhashtable.h @@ -395,6 +395,7 @@ static inline void rht_assign_unlock(struct bucket_table *tbl, rcu_assign_pointer(*bkt, (void *)obj); preempt_enable(); __release(bitlock); + bit_spin_wake(0, (unsigned long *) bkt); } /** |