On 04/17/2014 11:56 AM, Peter Zijlstra wrote:
On Thu, Apr 17, 2014 at 11:03:57AM -0400, Waiman Long wrote:+struct __qspinlock { + union { + atomic_t val; + struct { +#ifdef __LITTLE_ENDIAN + u16 locked_pending; + u16 tail; +#else + u16 tail; + u16 locked_pending; +#endif + }; + }; +}; + +/** + * clear_pending_set_locked - take ownership and clear the pending bit. + * @lock: Pointer to queue spinlock structure + * @val : Current value of the queue spinlock 32-bit word + * + * *,1,0 -> *,0,1 + */ +static __always_inline void +clear_pending_set_locked(struct qspinlock *lock, u32 val) +{ + struct __qspinlock *l = (void *)lock; + + ACCESS_ONCE(l->locked_pending) = 1;You lost the __constant_le16_to_cpu(_Q_LOCKED_VAL) there. The unconditional 1 is wrong. You also have to flip the bytes in locked_pending.
I don't think that is wrong. The lock byte is in the least significant 8 bits and the pending byte is the next higher significant 8 bits irrespective of the endian-ness. So a value of 1 in a 16-bit context means the lock byte is set, but the pending byte is cleared. The name "locked_pending" doesn't mean that locked variable is in a lower address than pending.
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