Subject: Re: [RFC PATCH] introduce sys_membarrier(): process-wide memory
 barrier (v5)
From: Steven Rostedt <rostedt@goodmis.org>
Reply-To: rostedt@goodmis.org
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org,
       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
       Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@elte.hu>,
       akpm@linux-foundation.org, josh@joshtriplett.org, tglx@linutronix.de,
       Valdis.Kletnieks@vt.edu, dhowells@redhat.com, laijs@cn.fujitsu.com,
       dipankar@in.ibm.com
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Date: Thu, 21 Jan 2010 11:32:09 -0500
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On Thu, 2010-01-21 at 11:22 -0500, Mathieu Desnoyers wrote:
> * Steven Rostedt (rostedt@goodmis.org) wrote:

> > You may also need spin_lock_irqsave, et al. variants too.
> 
> Yep, or we simply use the local_irq_save/restore separately. That could
> be a good idea given that only few specialized sites are affected.

If it gets used more often, then we need to consider RT. RT modifies
spin_lock_irqsave into a standard mutex that does not disable
interrupts. But if something does:

	local_irq_save(flags);
	spin_lock_mb(&lock);
	[...]

Then it will break RT (if lock is to be converted).

-- Steve


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