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Date: Thu, 17 Oct 2013 16:06:04 +0530
From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>,
        Ingo Molnar <mingo@kernel.org>, Andrea Arcangeli <aarcange@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/6] rcu: Create rcu_sync infrastructure
Message-ID: <20131017103604.GJ19729@linux.vnet.ibm.com>
Reply-To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
References: <20131008102505.404025673@infradead.org>
 <20131008103830.180541879@infradead.org>
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* Peter Zijlstra <peterz@infradead.org> [2013-10-08 12:25:07]:

> From: Oleg Nesterov <oleg@redhat.com>
> 
> It is functionally equivalent to
> 
>         struct rcu_sync_struct {
>                 atomic_t counter;
>         };
> 
>         static inline bool rcu_sync_is_idle(struct rcu_sync_struct *xxx)
>         {
>                 return atomic_read(&xxx->counter) == 0;
>         }
> 
>         static inline void rcu_sync_enter(struct rcu_sync_struct *xxx)
>         {
>                 atomic_inc(&xxx->counter);
>                 synchronize_sched();
>         }
> 
>         static inline void rcu_sync_enter(struct rcu_sync_struct *xxx)

Guess you meant rcu_sync_exit

>         {
>                 synchronize_sched();
>                 atomic_dec(&xxx->counter);
>         }
> 
> except: it records the state and synchronize_sched() is only called by
> rcu_sync_enter() and only if necessary.
> 

-- 
Thanks and Regards
Srikar Dronamraju