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Date: Mon, 22 Aug 2016 10:15:28 +0800 From: Wanpeng Li <kernellwp@...il.com> To: Waiman Long <waiman.long@....com> Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "the arch/x86 maintainers" <x86@...nel.org>, linux-alpha@...r.kernel.org, linux-ia64@...r.kernel.org, linux-s390 <linux-s390@...r.kernel.org>, linux-arch@...r.kernel.org, linux-doc@...r.kernel.org, Davidlohr Bueso <dave@...olabs.net>, Jason Low <jason.low2@...com>, Dave Chinner <david@...morbit.com>, Jonathan Corbet <corbet@....net>, Scott J Norton <scott.norton@....com>, Douglas Hatch <doug.hatch@....com> Subject: Re: [RFC PATCH-tip v4 07/10] locking/rwsem: Change RWSEM_WAITING_BIAS for better disambiguation 2016-08-20 0:21 GMT+08:00 Waiman Long <waiman.long@....com>: > On 08/19/2016 01:57 AM, Wanpeng Li wrote: >> >> 2016-08-19 5:11 GMT+08:00 Waiman Long<Waiman.Long@....com>: >>> >>> When the count value is in between 0 and RWSEM_WAITING_BIAS, there >>> are 2 possibilities. >>> Either a writer is present and there is no waiter >> >> count = 0xffff0001 >> >>> or there are waiters and readers. There is no easy way to >> >> count = 0xffff000X >> >> However, RWSEM_WAITING_BIAS is equal to 0xffff0000, so both these two >> cases are beyond RWSEM_WAITING_BIAS, right? >> >> Regards, >> Wanpeng Li > > > Perhaps I should make it clear that I am talking from a signed quantity > point of view (it is an atomic_long_t). So > > RWSEM_WAITING_BIAS < RWSEM_ACTIVE_WRITE_BIAS < 0 > > Hope this clarify your question. Yeah, thank you. :) Regards, Wanpeng Li
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