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Date: Mon, 25 May 2009 12:50:03 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Paul Mackerras <paulus@...ba.org> Cc: Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org, Corey Ashford <cjashfor@...ux.vnet.ibm.com>, Thomas Gleixner <tglx@...utronix.de> Subject: Re: [PATCH 2/2] perf_counter: optimize context switch between identical inherited contexts On Mon, 2009-05-25 at 12:38 +0200, Peter Zijlstra wrote: > On Mon, 2009-05-25 at 10:15 +1000, Paul Mackerras wrote: > > Peter Zijlstra writes: > > > > > Ingo just pointed out that there is nothing there to close the race with > > > attaching a counter. > > > > > > That is, you could end up attaching your counter to the wrong task. > > > > Good point. Doing the unclone in find_get_context would be a start, > > but the locking could get tricky (in fact we don't have any way to > > remove an inherited counter from a context, so we only have to worry > > about counters being attached). I'll work out a solution after I have > > digested your recent batch of patches. > > I'm currently staring at something like the below, trying to find races > etc.. ;-) > > attach vs destroy vs flip Hmm, it appears we only unclone ctx on remove, not attach.. how odd.. -- 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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