On 05/08/2014 03:00 PM, Peter Zijlstra wrote:
On Wed, May 07, 2014 at 11:01:35AM -0400, Waiman Long wrote:@@ -94,23 +94,29 @@ static inline struct mcs_spinlock *decode_tail(u32 tail) * can allow better optimization of the lock acquisition for the pending * bit holder. */ -#if _Q_PENDING_BITS == 8 - struct __qspinlock { union { atomic_t val; - struct { #ifdef __LITTLE_ENDIAN + u8 locked; + struct { u16 locked_pending; u16 tail; + }; #else + struct { u16 tail; u16 locked_pending; -#endif }; + struct { + u8 reserved[3]; + u8 locked; + }; +#endif }; }; +#if _Q_PENDING_BITS == 8That doesn't make sense, that struct __qspinlock only makes sense when _Q_PENDING_BITS == 8.
I need to use the locked field (the 2nd strcut) in get_qlock() where I grab the lock by setting the lock byte directly. Since the endian-aware structure is already in place, I reused it and have to expose it even when _Q_PENDING_BITS isn't 8. I will document that more clearly in the code to avoid this confusion.
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