Date: Thu, 19 Jan 2017 10:22:28 +0000 From: "Reshetova, Elena" <elena.reshetova@...el.com> To: Peter Zijlstra <peterz@...radead.org>, Eric Biggers <ebiggers3@...il.com> CC: "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, "keescook@...omium.org" <keescook@...omium.org>, "arnd@...db.de" <arnd@...db.de>, "tglx@...utronix.de" <tglx@...utronix.de>, "mingo@...hat.com" <mingo@...hat.com>, "Anvin, H Peter" <h.peter.anvin@...el.com>, "will.deacon@....com" <will.deacon@....com>, "dwindsor@...il.com" <dwindsor@...il.com>, "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org> Subject: RE: [RFCv2 PATCH 00/18] refcount_t API + usage > You again failed to reply to my last email on the subject. The initial > PaX thing was broken as heck, only later did you mention it got fixed. I > told you we could change to that for x86 if it could be proven to be > equivalent. I am confused on what is referred here as a fix.. Do you mean the earlier proposal to use cmpxchg instead of addl in the x86 assembly code? If yes, that indeed removes races, but when performance measurements were done, it was dismissed as being too costly to enforce on atomic by default. This had numbers on addl vs. cmpxchg: http://www.openwall.com/lists/kernel-hardening/2016/10/04/10 Best Regards, Elena.
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