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Date: Mon, 06 Apr 2020 11:39:19 +1000 From: Nicholas Piggin <npiggin@...il.com> To: Benjamin Herrenschmidt <benh@...nel.crashing.org>, Christophe Leroy <christophe.leroy@....fr>, Michael Ellerman <mpe@...erman.id.au>, msuchanek@...e.de, Paul Mackerras <paulus@...ba.org> Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org Subject: Re: [RFC PATCH v2 13/13] powerpc/kernel: Do not use READ_ONCE() to access current thread_info flags Christophe Leroy's on April 6, 2020 3:44 am: > current is a volatile pointer hold by r2 register. > > READ_ONCE() is not required. > > Before: 327 cycles on null_syscall > Before: 325 cycles on null_syscall Patches against Michael's next-test branch have a few small changes here. I need to look at the fallout on 64-bit code, although most likely it's not measurable so if it saves you a few cycles we can lean toward what ppc32 prefers. Same with the compat test. Thanks, Nick
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