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Date: Fri, 29 Aug 2008 10:29:40 -0400 (EDT) From: Steven Rostedt <rostedt@...dmis.org> To: John Kacur <jkacur@...il.com> cc: Andrew Morton <akpm@...ux-foundation.org>, mgross@...ux.intel.com, linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org, peterz@...radead.org, mingo@...e.hu, tglx@...utronix.de, arjan@...radead.org Subject: Re: [PATCH RFC] pm_qos_requirement might sleep On Fri, 29 Aug 2008, John Kacur wrote: > > Hi Andrew > > The purpose of the patch is to remove the spin_lock around the read in > the function pm_qos_requirement - since spinlocks can sleep in -rt and > this function is called from idle. I did propose a patch, that simply > removed the spinlock, since Peter Zilstra and others (yourself) point > out, the lock isn't needed to read a single word from memory. Although > the patch worked fine, Arjan objected to it, because it was not > symmetric. A reader of the code might wonder why it was locked in > other functions but not here. He suggested changing it to an atomic > type might be less confusing. The alternative which I like better > actually is to simply remove the lock in pm_qos_requirement and add a > comment for readers of the code. This is a much better changelog, and is what should have been written in the first place ;-) -- Steve -- 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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