Subject: Re: Kernel rwlock design, Multicore and IGMP

From: Peter Zijlstra <[email-masked]>
Date: Sat, 13 Nov 2010 23:53:46 +0100

On Fri, 2010-11-12 at 11:32 +0800, Cypher Wu wrote:
> It seems not a problem that read_lock() can be nested or not since
> rwlock doesn't have 'owner', 

You're mistaken.

> it's just that should we give
> write_lock() a priority than read_lock() since if there have a lot
> read_lock()s then they'll starve write_lock().

We rely on that behaviour. FWIW write preference locks will starve
readers.

> We should work out a well defined behavior so all the
> platform-dependent raw_rwlock has to design under that principle. 

We have that, all archs have read preference rwlock_t, they have to,
code relies on it.