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Date: Tue, 6 Apr 2010 20:15:40 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
cc: Avi Kivity <avi@redhat.com>, Darren Hart <dvhltc@us.ibm.com>,
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Subject: Re: [PATCH V2 0/6][RFC] futex: FUTEX_LOCK with optional adaptive
 spinning
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On Tue, 6 Apr 2010, Alan Cox wrote:

> > > IMO the best solution is to spin in userspace while the lock holder is
> > > running, fall into the kernel when it is scheduled out.
> > 
> > That's just not realistic as user space has no idea whether the lock
> > holder is running or not and when it's scheduled out without a syscall :)
> 
> Which is the real problem that wants addressing and can be addressed very
> cheaply. That would bring us up to par with 1970s RTOS environments ;)

Well, 1970's RTOSes had other features as well like preemption disable
mechanisms and other interesting stuff. I hope you're not going to
propose that next to bring us up to par with those :)

Thanks,

	tglx