From: Waiman Long <waiman.long@hpe.com>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org,
linux-s390 <linux-s390@vger.kernel.org>,
linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
Davidlohr Bueso <dave@stgolabs.net>,
Jason Low <jason.low2@hp.com>, Dave Chinner <david@fromorbit.com>,
Jonathan Corbet <corbet@lwn.net>,
Scott J Norton <scott.norton@hpe.com>,
Douglas Hatch <doug.hatch@hpe.com>
Subject: Re: [RFC PATCH-tip v4 07/10] locking/rwsem: Change RWSEM_WAITING_BIAS for better disambiguation
Date: Fri, 19 Aug 2016 12:21:57 -0400 [thread overview]
Message-ID: <57B73225.7020303@hpe.com> (raw)
In-Reply-To: <CANRm+CzfQFHDZDdBc+WxSkFPaE6x=b+PGBeEnnAqgmjDi=1DDA@mail.gmail.com>
On 08/19/2016 01:57 AM, Wanpeng Li wrote:
> 2016-08-19 5:11 GMT+08:00 Waiman Long<Waiman.Long@hpe.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.
Cheers,
Longman
next prev parent reply other threads:[~2016-08-19 16:21 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-18 21:11 [RFC PATCH-tip v4 00/10] locking/rwsem: Enable reader optimistic spinning Waiman Long
2016-08-18 21:11 ` [RFC PATCH-tip v4 01/10] locking/osq: Make lock/unlock proper acquire/release barrier Waiman Long
2016-10-04 19:06 ` Davidlohr Bueso
2016-10-04 21:28 ` Jason Low
2016-10-05 12:19 ` Waiman Long
2016-10-05 15:11 ` Waiman Long
2016-10-06 5:47 ` Davidlohr Bueso
2016-10-06 19:30 ` Waiman Long
2016-10-10 5:39 ` [PATCH] locking/osq: Provide proper lock/unlock and relaxed flavors Davidlohr Bueso
2016-10-06 19:31 ` [RFC PATCH-tip v4 01/10] locking/osq: Make lock/unlock proper acquire/release barrier Jason Low
2016-08-18 21:11 ` [RFC PATCH-tip v4 02/10] locking/rwsem: Stop active read lock ASAP Waiman Long
2016-10-06 18:17 ` Davidlohr Bueso
2016-10-06 21:47 ` Dave Chinner
2016-10-06 22:51 ` Davidlohr Bueso
2016-10-07 21:45 ` Waiman Long
2016-10-09 15:17 ` Christoph Hellwig
2016-10-10 6:07 ` Dave Chinner
2016-10-10 9:34 ` Christoph Hellwig
2016-10-11 21:06 ` Dave Chinner
2016-10-16 5:57 ` Christoph Hellwig
2016-08-18 21:11 ` [RFC PATCH-tip v4 03/10] locking/rwsem: Make rwsem_spin_on_owner() return a tri-state value Waiman Long
2016-08-18 21:11 ` [RFC PATCH-tip v4 04/10] locking/rwsem: Enable count-based spinning on reader Waiman Long
2016-08-18 21:11 ` [RFC PATCH-tip v4 05/10] locking/rwsem: move down rwsem_down_read_failed function Waiman Long
2016-08-18 21:11 ` [RFC PATCH-tip v4 06/10] locking/rwsem: Move common rwsem macros to asm-generic/rwsem_types.h Waiman Long
2016-08-18 21:11 ` [RFC PATCH-tip v4 07/10] locking/rwsem: Change RWSEM_WAITING_BIAS for better disambiguation Waiman Long
2016-08-19 5:57 ` Wanpeng Li
2016-08-19 16:21 ` Waiman Long [this message]
2016-08-22 2:15 ` Wanpeng Li
2016-08-18 21:11 ` [RFC PATCH-tip v4 08/10] locking/rwsem: Enable spinning readers Waiman Long
2016-08-18 21:11 ` [RFC PATCH-tip v4 09/10] locking/rwsem: Enable reactivation of reader spinning Waiman Long
2016-08-18 21:11 ` [RFC PATCH-tip v4 10/10] locking/rwsem: Add a boot parameter to reader spinning threshold Waiman Long
2016-08-24 1:46 ` [lkp] [locking/rwsem] INFO: rcu_preempt detected stalls on CPUs/tasks kernel test robot
2016-08-24 4:00 ` [RFC PATCH-tip v4 10/10] locking/rwsem: Add a boot parameter to reader spinning threshold Davidlohr Bueso
2016-08-24 18:39 ` Waiman Long
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