From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
"H. Peter Anvin" <hpa@zytor.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>
Subject: Re: [PATCH v4 1/5] getcpu_cache system call: cache CPU number of running thread
Date: Sat, 27 Feb 2016 23:53:56 +0000 (UTC) [thread overview]
Message-ID: <1401667361.10273.1456617236327.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <CA+55aFysWipEagSdgeXbLx+Au4vomvyttdNFJtM+HffmBECQiA@mail.gmail.com>
----- On Feb 27, 2016, at 1:35 PM, 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.
AFAIU, this "post_commit_ip" field is expected to be updated
with a single-copy-store by user-space. If we want to handle both
32-bit and 64-bit processes, how do you recommend doing this
without an unsigned long type ?
A 64-bit integer would not be a single-copy store for
32-bit processes, but a 32-bit integer would not be large
enough for 64-bit processes.
Would a
union {
uint32_t val32;
uint64_t val64;
} field;
be an acceptable option ? Then the kernel could use
one field or the other depending on the process bitness.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2016-02-27 23:54 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-23 23:28 [PATCH v4 0/5] getcpu_cache system call for 4.6 Mathieu Desnoyers
2016-02-23 23:28 ` [PATCH v4 1/5] getcpu_cache system call: cache CPU number of running thread Mathieu Desnoyers
2016-02-24 11:11 ` Thomas Gleixner
2016-02-24 17:17 ` Mathieu Desnoyers
2016-02-25 23:32 ` Rasmus Villemoes
2016-02-26 17:47 ` Mathieu Desnoyers
2016-02-25 9:56 ` Peter Zijlstra
2016-02-25 16:55 ` Mathieu Desnoyers
2016-02-25 17:04 ` Peter Zijlstra
2016-02-25 17:17 ` Mathieu Desnoyers
2016-02-26 11:33 ` Peter Zijlstra
2016-02-26 16:29 ` Thomas Gleixner
2016-02-26 17:20 ` Mathieu Desnoyers
2016-02-26 18:01 ` Thomas Gleixner
2016-02-26 20:24 ` Mathieu Desnoyers
2016-02-26 23:04 ` H. Peter Anvin
2016-02-27 0:40 ` Mathieu Desnoyers
2016-02-27 6:24 ` H. Peter Anvin
2016-02-27 14:15 ` Mathieu Desnoyers
2016-02-27 14:58 ` Peter Zijlstra
2016-02-27 18:35 ` Linus Torvalds
2016-02-27 19:01 ` H. Peter Anvin
2016-02-27 23:53 ` Mathieu Desnoyers [this message]
[not found] ` <CA+55aFwcgwRxvVBz5kk_3O8dESXAGJ4KHBkf=pSXjiS7Xh4NwA@mail.gmail.com>
[not found] ` <1082926946.10326.1456619994590.JavaMail.zimbra@efficios.com>
2016-02-28 0:57 ` Linus Torvalds
2016-02-28 14:32 ` Mathieu Desnoyers
2016-02-29 10:35 ` Peter Zijlstra
2016-03-01 20:23 ` Mathieu Desnoyers
2016-03-01 21:32 ` Peter Zijlstra
2016-03-01 21:36 ` Peter Zijlstra
2016-03-01 21:47 ` H. Peter Anvin
2016-03-02 10:34 ` Peter Zijlstra
2016-02-29 10:32 ` Peter Zijlstra
2016-02-29 10:39 ` Arnd Bergmann
2016-02-29 12:41 ` Mathieu Desnoyers
2016-02-29 13:08 ` Arnd Bergmann
2016-02-29 18:19 ` H. Peter Anvin
2016-03-02 10:44 ` Geert Uytterhoeven
2016-03-01 18:25 ` H. Peter Anvin
2016-03-01 18:40 ` Mathieu Desnoyers
2016-02-28 13:07 ` Geert Uytterhoeven
2016-02-28 16:21 ` Linus Torvalds
2016-02-29 10:01 ` Peter Zijlstra
2016-02-27 15:04 ` H. Peter Anvin
2016-02-23 23:28 ` [PATCH v4 2/5] getcpu_cache: ARM resume notifier Mathieu Desnoyers
2016-02-23 23:28 ` [PATCH v4 3/5] getcpu_cache: wire up ARM system call Mathieu Desnoyers
2016-02-24 0:54 ` kbuild test robot
2016-02-24 1:05 ` [PATCH v4 (updated)] " Mathieu Desnoyers
2016-02-24 5:28 ` kbuild test robot
2016-02-24 6:54 ` kbuild test robot
2016-02-23 23:28 ` [PATCH v4 4/5] getcpu_cache: x86 32/64 resume notifier Mathieu Desnoyers
2016-02-23 23:28 ` [PATCH v4 5/5] getcpu_cache: wire up x86 32/64 system call Mathieu Desnoyers
2016-02-24 1:36 ` [PATCH v4 0/5] getcpu_cache system call for 4.6 H. Peter Anvin
2016-02-24 4:09 ` Mathieu Desnoyers
2016-02-24 20:07 ` H. Peter Anvin
2016-02-24 22:38 ` Mathieu Desnoyers
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