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Date: Tue, 02 Oct 2007 23:18:22 -0700 From: "H. Peter Anvin" <hpa@...or.com> To: Nick Piggin <nickpiggin@...oo.com.au> CC: Chuck Ebbert <cebbert@...hat.com>, Arjan van de Ven <arjan@...radead.org>, Kirill Korotaev <dev@...nvz.org>, Andrew Morton <akpm@...l.org>, Andi Kleen <ak@...e.de>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, devel@...nvz.org Subject: Re: [PATCH] mark read_crX() asm code as volatile Nick Piggin wrote: >> >> This should work because the result gets used before reading again: >> >> read_cr3(a); >> write_cr3(a | 1); >> read_cr3(a); >> >> But this might be reordered so that b gets read before the write: >> >> read_cr3(a); >> write_cr3(a | 1); >> read_cr3(b); >> >> ? > > I don't see how, as write_cr3 clobbers memory. Because read_cr3() doesn't depend on memory, and b could be stored in a register. -hpa - 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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