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Date: Tue, 10 Sep 2013 14:43:06 -0700 From: Linus Torvalds <torvalds@...ux-foundation.org> To: Peter Zijlstra <peterz@...radead.org> Cc: Ingo Molnar <mingo@...nel.org>, Andi Kleen <ak@...ux.intel.com>, Peter Anvin <hpa@...or.com>, Mike Galbraith <bitbucket@...ine.de>, Thomas Gleixner <tglx@...utronix.de>, Arjan van de Ven <arjan@...ux.intel.com>, Frederic Weisbecker <fweisbec@...il.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org> Subject: Re: [PATCH 0/7] preempt_count rework -v2 On Tue, Sep 10, 2013 at 2:25 PM, Peter Zijlstra <peterz@...radead.org> wrote: > > Here's one that builds and boots on kvm until wanting to mount root. > > I'm not entirely sure on the "ir" vs "er" thing and atomic64_t and > local_t are inconsistent wrt that so I'm too. "i" is "any constant", while "e" is "32-bit signed constant". And I think all of the 64-bit ones should probably be "e", because afaik there is no way to add a 64-bit constant directly to memory (you have to load it into a register first). Of course, in reality, the constant is always just 1 or -1 or something like that, so nobody will ever notice the incorrect case... And it doesn't matter for the 32-bit cases, obviously, but we could just make them all be "e" for simplicity. That said, looking at your patch, I get the *very* strong feeling that we could make a macro that does all the repetitions for us, and then have a GENERATE_RMW(atomic_sub_and_test, LOCK_PREFIX "subl", "e", "") GENERATE_RMW(atomic_dec_and_test, LOCK_PREFIX "decl", "e", "") .. GENERATE_RMW(atomic_add_negative, LOCK_PREFIX "addl", "s", "") GENERATE_RMW(local_sub_and_test, "subl", "e", __percpu_prefix) ... etc. I'm sure the macro would be nasty as hell (and I bet it needs a few more arguments), but then we'd avoid the repetition.. Linus -- 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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