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

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Message-ID: <20190411081224.GB4038@hirez.programming.kicks-ass.net>
Date:   Thu, 11 Apr 2019 10:12:24 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Waiman Long <longman@...hat.com>
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 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.