On Mon, May 26, 2014 at 01:27:55PM +0800, Lai Jiangshan wrote: > changing pwq: > install pwq > lock(pool->lock) > put_pwq(); > unlock(pool->lock) > > __queue_work(): > lock(pool->lock) > test ref and find it zero; > see the installation here; > it is guaranteed to get the installed pwq on the immediate next try. > unlock() > retry.
The fact that pool->lock locking happens to provide enough barrier for the above to work is an accidental implementation detail. We theoretically can move refcnting out of pool->lock. Nothing semantically guarantees that barrier to be there to interlock pwq qinstallation and the last put. Removing that cpu_relax() doesn't buy us *ANYTHING* and removing that with rationale of making it go faster would easily win pointless micro optimization award of the year. Just let it go. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
