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: <20190412070545.GF11158@hirez.programming.kicks-ass.net>
Date:   Fri, 12 Apr 2019 09:05:45 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Waiman Long <longman@...hat.com>, 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 Fri, Apr 12, 2019 at 09:02:09AM +0200, Ingo Molnar wrote:
> 
> * Waiman Long <longman@...hat.com> wrote:
> 
> > 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.
> 
> Could you please post the next series against tip:WIP.locking/core, which 
> is already being dogfood-ed in -tip and which I'm running on my desktop? 
> I'll backmerge any fixes as needed/requested.

Urgh, please no, that's going to be hell to review :/