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Date: Tue, 03 Dec 2013 14:42:02 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Oleg Nesterov <oleg@redhat.com>
CC: Linus Torvalds <torvalds@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>, Peter Zijlstra <peterz@infradead.org>,
        Jiri Kosina <jkosina@suse.cz>, Andi Kleen <andi@firstfloor.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Andi Kleen <ak@linux.intel.com>, Ingo Molnar <mingo@kernel.org>,
        Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH?] uprobes: change uprobe_write_opcode() to modify the
 page directly
References: <20131129200532.GA13561@redhat.com> <alpine.LRH.2.00.1311300023070.9932@twin.jikos.cz> <CA+55aFxJGidV4=ot0z_Va8+y2QWTDYghTm1Gin84StZ+R1SfXg@mail.gmail.com> <20131203184909.GA17571@redhat.com> <CA+55aFw3N=iNW2Ej6w7oksX5JDVis7QL=9X9D7JB_tKZhrjsLw@mail.gmail.com> <529E2F0C.8070405@zytor.com> <20131203200147.GB19083@redhat.com> <529E3D4C.9070403@zytor.com> <20131203203826.GA24812@redhat.com> <e6082bc4-c910-4a36-9e40-624b9319f5fb@email.android.com> <20131203205400.GA25735@redhat.com>
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On 12/03/2013 12:54 PM, Oleg Nesterov wrote:
> On 12/03, H. Peter Anvin wrote:
>>
>> There is no architecture-independent way to make code globally visible.
> 
> Then I probably misunderstood "globally". Or something else.
> 
> So do you think the patch I sent is wrong? Why?
> 

It is wrong in the sense that without an architecture-specific
synchronization at the end it is not guaranteed to work.  It will work
fine on x86 and presumably any other architecture where icache-dcache
coherency is enforced in hardware (I am *guessing* that includes all or
most SMP platforms, but it is definitely *not* true on all UP platforms.)

	-hpa