linux-kernel - Re: [PATCH-tip v3 02/14] locking/rwsem: Make owner available even if !CONFIG_RWSEM_SPIN_ON

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Date:   Thu, 11 Apr 2019 12:03:15 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Davidlohr Bueso <dave@...olabs.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        huang ying <huang.ying.caritas@...il.com>
Subject: Re: [PATCH-tip v3 02/14] locking/rwsem: Make owner available even if
 !CONFIG_RWSEM_SPIN_ON_OWNER

On 04/11/2019 04:12 AM, Peter Zijlstra wrote:
> On Wed, Apr 10, 2019 at 02:42:19PM -0400, Waiman Long wrote:
>> The owner field in the rw_semaphore structure is used primarily for
>> optimistic spinning. However, identifying the rwsem owner can also be
>> helpful in debugging as well as tracing locking related issues when
>> analyzing crash dump. The owner field may also store state information
>> that can be important to the operation of the rwsem.
>>
>> So the owner field is now made a permanent member of the rw_semaphore
>> structure irrespective of CONFIG_RWSEM_SPIN_ON_OWNER.
> sem->owner is still initialized under CONFIG_RWSEM_SPIN_ON_OWNER.

Oh, you are right. I missed that part. I will fix it in the next version.

Cheers,
Longman