From: Torvald Riegel <triegel@redhat.com>
To: Stefan Liebler <stli@linux.vnet.ibm.com>
Cc: libc-alpha@sourceware.org, "Joseph S. Myers" <joseph@codesourcery.com>
Subject: Re: [PATCH 1/2] [PING] Optimize generic spinlock code and use C11 like atomic macros.
Date: Wed, 31 May 2017 16:48:00 -0000 [thread overview]
Message-ID: <1496249292.5890.1034.camel@redhat.com> (raw)
In-Reply-To: <f25d852a-fec9-c6a3-c781-437f94a06800@linux.vnet.ibm.com>
On Wed, 2017-05-31 at 10:29 +0200, Stefan Liebler wrote:
> On 05/30/2017 09:18 AM, Torvald Riegel wrote:
> > On Wed, 2017-05-10 at 15:00 +0200, Stefan Liebler wrote:
> >> On 05/03/2017 01:38 PM, Stefan Liebler wrote:
> >>> On 04/25/2017 08:46 AM, Stefan Liebler wrote:
> >>>> On 04/18/2017 03:09 PM, Stefan Liebler wrote:
> >>>>> On 04/10/2017 01:59 PM, Stefan Liebler wrote:
> >>>>>> On 04/09/2017 03:51 PM, Torvald Riegel wrote:
> >>>>>>> On Fri, 2017-04-07 at 18:22 +0200, Stefan Liebler wrote:
> >>>>>>>> @architecture maintainers:
> >>>>>>>> I've added defines of ATOMIC_EXCHANGE_USES_CAS in the architecture
> >>>>>>>> specific atomic-machine.h files.
> >>>>>>>> See comment in include/atomic.h:
> >>>>>>>> /* ATOMIC_EXCHANGE_USES_CAS is equal to 1 if atomic_exchange
> >>>>>>>> operations
> >>>>>>>> are implemented based on a CAS loop; otherwise, this is 0 and we
> >>>>>>>> assume
> >>>>>>>> that the atomic_exchange operations could provide better
> >>>>>>>> performance
> >>>>>>>> than a CAS loop. */
> >>>>>>>>
> >>>>>>>> Can review the definition to 0 or 1 in the atomic-machine.h file of
> >>>>>>>> your
> >>>>>>>> architecture, please?
> >>>>>
> >>>>>
> >>>>> PING
> >>>>>
> >>>> PING
> >>>
> >>> PING
> >>
> >> PING
> >>
> >> @Torvald:
> >> I'm not sure if we will get answers from everybody.
> >> What do you propose how to proceed with the definitions of
> >> ATOMIC_EXCHANGE_USES_CAS?
> >
> > Which archs are still missing? If maintainers don't reply, I suggest we
> > do our best to figure out what's the case for each missing arch, and add
> > a note that it should be checked eventually (eg, /* XXX Is this actually
> > correct? */) to the code, and then commit. Please CC: me on such a
> > patch, so I can have a last look at it.
> >
>
> We are sure for these archs:
> -aarch64: #define ATOMIC_EXCHANGE_USES_CAS 0
> -i386/x86: #define ATOMIC_EXCHANGE_USES_CAS 0
> -mips: #define ATOMIC_EXCHANGE_USES_CAS 0/1
> -powerpc: #define ATOMIC_EXCHANGE_USES_CAS 1
> -s390: #define ATOMIC_EXCHANGE_USES_CAS 1
> -tile: #define ATOMIC_EXCHANGE_USES_CAS 0
>
> Nobody answered for these archs:
> -alpha: #define ATOMIC_EXCHANGE_USES_CAS 1
> -arm: #define ATOMIC_EXCHANGE_USES_CAS 1
> -hppa: #define ATOMIC_EXCHANGE_USES_CAS 1
> -ia64: #define ATOMIC_EXCHANGE_USES_CAS 0
> -m68k: #define ATOMIC_EXCHANGE_USES_CAS 1
> -microblaze: #define ATOMIC_EXCHANGE_USES_CAS 1
> -nios2: #define ATOMIC_EXCHANGE_USES_CAS 1
> -sh: #define ATOMIC_EXCHANGE_USES_CAS 1
> -sparc: #define ATOMIC_EXCHANGE_USES_CAS 1
Joseph, can you clarify for arm?
> In the two of three sparc files ...
> ./sysdeps/sparc/sparc64/atomic-machine.h
> ./sysdeps/sparc/sparc32/sparcv9/atomic-machine.h
> ... there is the swap instruction in macro atomic_exchange_acq
> for 4 bytes. Other sizes are aborted or done by CAS.
> Shall we use #define ATOMIC_EXCHANGE_USES_CAS 0 here?
I suggest we let the sparc maintainer take care of that (though we could
set it to 0 for sparc32 I guess).
>
> I've attached the current version with
> /* XXX Is this actually correct? */
> for all architecture for which we didn't get an answer.
>
> The second patch "S390: Use generic spinlock code." remains the same.
I'd wait for a few more days to give Joseph time to respond, and then
commit if there are no objections or further input. I think maintainers
had enough time to comment, and you pinged them often enough already.
Thanks for being patient! :)
next prev parent reply other threads:[~2017-05-31 16:48 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-16 16:32 [PATCH 1/2] " Stefan Liebler
2016-12-16 16:32 ` [PATCH 2/2] S390: Use generic spinlock code Stefan Liebler
2017-02-08 14:49 ` Stefan Liebler
2017-02-13 20:39 ` Torvald Riegel
2017-02-15 16:26 ` Stefan Liebler
2017-02-18 17:05 ` Torvald Riegel
2017-03-14 15:55 ` Stefan Liebler
2017-03-21 15:43 ` Stefan Liebler
2017-04-06 12:27 ` Torvald Riegel
2016-12-19 12:14 ` [PATCH 1/2] Optimize generic spinlock code and use C11 like atomic macros Szabolcs Nagy
2017-02-08 14:49 ` Stefan Liebler
2017-02-13 20:29 ` Torvald Riegel
2017-02-15 9:36 ` Stefan Liebler
2017-02-18 16:57 ` Torvald Riegel
2017-02-19 9:20 ` Florian Weimer
2017-02-20 13:11 ` Torvald Riegel
2017-02-26 7:55 ` Florian Weimer
2017-02-26 20:06 ` Torvald Riegel
2017-02-26 20:29 ` Florian Weimer
2017-02-26 20:35 ` Torvald Riegel
2017-02-27 17:57 ` Szabolcs Nagy
2017-02-28 7:15 ` Torvald Riegel
2017-03-14 15:55 ` Stefan Liebler
2017-02-20 12:15 ` Stefan Liebler
2017-02-20 13:51 ` Torvald Riegel
2017-03-14 15:55 ` Stefan Liebler
2017-03-21 15:43 ` Stefan Liebler
2017-03-22 12:56 ` Szabolcs Nagy
2017-03-23 16:16 ` Stefan Liebler
2017-03-23 17:52 ` Szabolcs Nagy
2017-04-06 12:04 ` Torvald Riegel
2017-03-27 13:08 ` Stefan Liebler
2017-04-04 10:29 ` [PING] " Stefan Liebler
2017-03-29 14:16 ` Stefan Liebler
2017-04-06 14:00 ` Torvald Riegel
2017-04-07 16:23 ` Stefan Liebler
2017-04-09 13:51 ` Torvald Riegel
2017-04-10 12:00 ` Stefan Liebler
2017-04-18 13:09 ` Stefan Liebler
2017-04-25 6:47 ` Stefan Liebler
2017-05-03 11:38 ` [PATCH 1/2] [PING] " Stefan Liebler
2017-05-10 13:00 ` Stefan Liebler
2017-05-17 13:09 ` Stefan Liebler
2017-05-24 6:37 ` Stefan Liebler
2017-05-30 7:18 ` Torvald Riegel
2017-05-31 8:29 ` Stefan Liebler
2017-05-31 16:48 ` Torvald Riegel [this message]
2017-06-01 13:40 ` Joseph Myers
2017-06-01 14:33 ` Torvald Riegel
2017-06-06 7:51 ` [PATCH 1/2] [COMMITTED] " Stefan Liebler
2017-04-10 8:17 ` [PATCH 1/2] " Andreas Schwab
2017-04-10 12:00 ` Stefan Liebler
2017-04-10 13:36 ` Andreas Schwab
2017-04-11 7:06 ` Stefan Liebler
2017-04-11 8:45 ` Andreas Schwab
2017-04-11 10:15 ` Stefan Liebler
2017-04-11 12:05 ` Andreas Schwab
2017-04-11 12:19 ` Stefan Liebler
2017-04-11 13:08 ` Zack Weinberg
2017-04-13 16:36 ` Torvald Riegel
2017-05-30 21:00 ` Tulio Magno Quites Machado Filho
2017-04-18 21:17 ` Joseph Myers
2017-04-19 8:27 ` Stefan Liebler
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