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Subject: Re: [PATCH v4 1/2] locking/rwsem: Add DEBUG_RWSEMS to look for
 lock/unlock mismatches
To:     Davidlohr Bueso <dave@stgolabs.net>
Cc:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-kernel@vger.kernel.org
References: <1522246852-17501-1-git-send-email-longman@redhat.com>
 <1522246852-17501-2-git-send-email-longman@redhat.com>
 <20180329013224.tfryvl6lv5i72jwm@linux-n805>
From:   Waiman Long <longman@redhat.com>
Organization: Red Hat
Message-ID: <1b8d58b1-faf3-f210-7356-9d67930a2efb@redhat.com>
Date:   Thu, 29 Mar 2018 10:55:44 -0400
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On 03/28/2018 09:32 PM, Davidlohr Bueso wrote:
> On Wed, 28 Mar 2018, Waiman Long wrote:
>
>> +config DEBUG_RWSEMS
>> +    bool "RW Semaphore debugging: basic checks"
>> +    depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER
>
> Why depend on RWSEM_SPIN_ON_OWNER? Doesn't everyone benefit from this?
> For example, DEBUG_MUTEXES does not need it.
>
> Thanks,
> Davidlohr

Because it checks the owner field which is present only if
RWSEM_SPIN_ON_OWNER is defined. Mutex is different in the sense that the
owner field is always there no matter if MUTEX_SPIN_ON_OWNER is set or not.

Cheers,
Longman