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Date: Thu, 08 Mar 2012 22:37:05 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Steven Rostedt <rostedt@...dmis.org> Cc: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>, linux-rt-users <linux-rt-users@...r.kernel.org> Subject: Re: [ANNOUNCE] 3.2.9-rt17 On Thu, 2012-03-08 at 16:36 -0500, Steven Rostedt wrote: > On Thu, 2012-03-08 at 22:28 +0100, Peter Zijlstra wrote: > > On Thu, 2012-03-08 at 16:25 -0500, Steven Rostedt wrote: > > > > > > How would this be different than what mainline does? When the lock is > > > released, it will wake up the other task. > > > > mainline has ticket locks, the rt-mutex stuff has equal priority lock > > stealing, waking up the blocked task will take so long our running loop > > will have re-acquired ->d_lock again before it even gets to trying. > > And we have adaptive mutexes. > > So we wake up the task (now with the higher priority), by the time it > wakes up, the original task retook the lock. But because of adaptive > mutexes, as this task takes the lock it notices that the owner is still > running, and it will spin and not sleep. > > Now when the original task releases the lock again, the other task can > take it just like it does on mainline. Now interleave it with a third task of even higher priority that puts the spinner to sleep. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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