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From: Waiman Long <longman@redhat.com>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
"Theodore Y. Ts'o" <tytso@mit.edu>,
Oleg Nesterov <oleg@redhat.com>, Jan Kara <jack@suse.cz>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v3 2/2] locking/percpu-rwsem: Annotate rwsem ownership transfer by setting RWSEM_OWNER_UNKNOWN
Date: Tue, 15 May 2018 14:45:57 -0400 [thread overview]
Message-ID: <e011289a-e13a-8839-7a48-eb6e58f5eaa7@redhat.com> (raw)
In-Reply-To: <CAOQ4uxj246koNjek_b=nP_Jf7HzL2v-KFO=RPG963YC7RJrCpg@mail.gmail.com>
On 05/15/2018 02:05 PM, Amir Goldstein wrote:
> On Tue, May 15, 2018 at 9:02 PM, Waiman Long <longman@redhat.com> wrote:
>> On 05/15/2018 01:58 PM, Peter Zijlstra wrote:
>>> On Tue, May 15, 2018 at 01:38:04PM -0400, Waiman Long wrote:
>>>> +/*
>>>> + * Owner value to indicate the rwsem's owner is not currently known.
>>>> + */
>>>> +#define RWSEM_OWNER_UNKNOWN ((struct task_struct *)-1)
>>> It might be nice to comment that this works and relies on having that
>>> ANON_OWNER bit set.
>> I am just trying not to expose internal working of rwsem, but I can
>> document that one of the bits is the real deal without specifying which one.
>>
> BUILD_BUG_ON(!rwsem_has_anonymous_owner(RWSEM_OWNER_UNKNOWN))
> inside rwsem.c and comment above to explain it.
Yes, it is a good idea. I will do that.
-Longman
next prev parent reply other threads:[~2018-05-15 18:46 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-15 17:38 [PATCH v3 0/2] locking/rwsem: Fix DEBUG_RWSEM warning from thaw_super() Waiman Long
2018-05-15 17:38 ` [PATCH v3 1/2] locking/rwsem: Add a new RWSEM_ANONYMOUSLY_OWNED flag Waiman Long
2018-05-15 17:46 ` Peter Zijlstra
2018-05-15 17:48 ` Waiman Long
2018-05-15 17:48 ` Peter Zijlstra
2018-05-15 17:52 ` Waiman Long
2018-05-15 17:55 ` Peter Zijlstra
2018-05-15 17:56 ` Waiman Long
2018-05-15 18:02 ` Peter Zijlstra
2018-05-15 17:38 ` [PATCH v3 2/2] locking/percpu-rwsem: Annotate rwsem ownership transfer by setting RWSEM_OWNER_UNKNOWN Waiman Long
2018-05-15 17:58 ` Peter Zijlstra
2018-05-15 18:02 ` Waiman Long
2018-05-15 18:05 ` Amir Goldstein
2018-05-15 18:45 ` Waiman Long [this message]
2018-05-15 18:05 ` Peter Zijlstra
2018-05-15 18:35 ` Waiman Long
2018-05-15 18:02 ` Matthew Wilcox
2018-05-15 18:07 ` Peter Zijlstra
2018-05-15 18:45 ` Waiman Long
2018-05-15 21:21 ` Matthew Wilcox
2018-05-15 21:30 ` Waiman Long
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