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Subject: Re: [PATCH v4 1/5] getcpu_cache system call: cache CPU number of running thread
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Sat, 27 Feb 2016 11:01:49 -0800
To: Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>
CC: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Russell King <linux@arm.linux.org.uk>, Ingo Molnar <mingo@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-api <linux-api@vger.kernel.org>, Paul Turner <pjt@google.com>,
        Andrew Hunter <ahh@google.com>, Andy Lutomirski <luto@amacapital.net>,
        Andi Kleen <andi@firstfloor.org>, Dave Watson <davejwatson@fb.com>,
        Chris Lameter <cl@linux.com>, Ben Maurer <bmaurer@fb.com>,
        rostedt <rostedt@goodmis.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Josh Triplett <josh@joshtriplett.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>
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On February 27, 2016 10:35:28 AM PST, Linus Torvalds <torvalds@linux-foundation.org> wrote:
>On Sat, Feb 27, 2016 at 6:58 AM, Peter Zijlstra <peterz@infradead.org>
>wrote:
>>
>> Paul's patches have the following structure:
>>
>> struct thread_local_abi {
>>         union {
>>                 struct {
>>                         u32     cpu_id;
>>                         u32     seq;
>>                 };
>>                 u64 cpu_seq;
>>         };
>>         unsigned long post_commit_ip;
>> };
>
>Please don't do "unsigned long" in ABI structures any more.
>
>Make it u64, and make sure it is 64-bit aligned (which it would be in
>this case). Make it so that we don't have to have separate compat
>paths.
>
>               Linus

Yes, if we have to do compat crap for this entire new ABI path I think I'll scream.
-- 
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