From: John Stultz <john.stultz@linaro.org>
To: Richard Cochran <richardcochran@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
linux-kernel <linux-kernel@vger.kernel.org>,
Tony Luck <tony.luck@intel.com>,
Paul Mackerras <paulus@samba.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Paul Turner <pjt@google.com>,
Steven Rostedt <rostedt@goodmis.org>,
Prarit Bhargava <prarit@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 0/6][RFC] Rework vsyscall to avoid truncation/rounding issue in timekeeping core
Date: Wed, 19 Sep 2012 10:54:05 -0700 [thread overview]
Message-ID: <505A06BD.6000406@linaro.org> (raw)
In-Reply-To: <20120919170347.GA2232@netboy.at.omicron.at>
On 09/19/2012 10:03 AM, Richard Cochran wrote:
> On Wed, Sep 19, 2012 at 09:31:35AM -0700, John Stultz wrote:
>> With powerpc, there is no arch specific kernel code involved, its
>> just a data structure the kernel exports that is accessible to
>> userland. The execution logic lives in userland libraries, or
>> sometimes application code itself.
> I took a brief look at arch/powerpc/kernel/vdso32/gettimeofday.S and
> arch/powerpc/kernel/vdso64/gettimeofday.S, and I see what looks a lot
> like functions
Sorry, yes. My statement wasn't subtle enough (and I may be confusing my
history).
You are right, there is arch specific code involved, but the data
structure that is exported is considered part of the abi since some
applications access it directly.
See the comments and structure in:
arch/powerpc/include/asm/vdso_datapage.h
> $ find arch/powerpc/kernel/vdso* -name gettimeofday.S|xargs grep FUNCTION_BEGIN
>
> arch/powerpc/kernel/vdso32/gettimeofday.S:V_FUNCTION_BEGIN(__kernel_gettimeofday)
> arch/powerpc/kernel/vdso32/gettimeofday.S:V_FUNCTION_BEGIN(__kernel_clock_gettime)
> arch/powerpc/kernel/vdso32/gettimeofday.S:V_FUNCTION_BEGIN(__kernel_clock_getres)
> arch/powerpc/kernel/vdso64/gettimeofday.S:V_FUNCTION_BEGIN(__kernel_gettimeofday)
> arch/powerpc/kernel/vdso64/gettimeofday.S:V_FUNCTION_BEGIN(__kernel_clock_gettime)
> arch/powerpc/kernel/vdso64/gettimeofday.S:V_FUNCTION_BEGIN(__kernel_clock_getres)
> arch/powerpc/kernel/vdso64/gettimeofday.S:V_FUNCTION_BEGIN(__do_get_tspec)
>
> and I wonder whether these could be done in C instead.
Possibly, but I suspect they're in asm for performance reasons.
Paul/Ben: Do you have any thoughts here?
thanks
-john
next prev parent reply other threads:[~2012-09-19 17:55 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-17 22:04 [PATCH 0/6][RFC] Rework vsyscall to avoid truncation/rounding issue in timekeeping core John Stultz
2012-09-17 22:04 ` [PATCH 1/6][RFC] time: Move timekeeper structure to timekeeper_internal.h for vsyscall changes John Stultz
2012-09-17 22:04 ` [PATCH 2/6][RFC] time: Move update_vsyscall definitions to timekeeper_internal.h John Stultz
2012-09-27 3:14 ` Paul Mackerras
2012-09-17 22:04 ` [PATCH 3/6][RFC] time: Convert CONFIG_GENERIC_TIME_VSYSCALL to CONFIG_GENERIC_TIME_VSYSCALL_OLD John Stultz
2012-09-27 3:14 ` Paul Mackerras
2012-09-17 22:04 ` [PATCH 4/6][RFC] time: Introduce new GENERIC_TIME_VSYSCALL John Stultz
2012-09-17 22:05 ` [PATCH 5/6][RFC] time: Only do nanosecond rounding on GENERIC_TIME_VSYSCALL_OLD systems John Stultz
2012-09-17 22:05 ` [PATCH 6/6][RFC] time: Convert x86_64 to using new update_vsyscall John Stultz
2012-09-17 23:49 ` [PATCH 0/6][RFC] Rework vsyscall to avoid truncation/rounding issue in timekeeping core Andy Lutomirski
2012-09-18 0:20 ` John Stultz
2012-09-18 0:43 ` Andy Lutomirski
2012-09-18 18:02 ` Richard Cochran
2012-09-18 18:17 ` Andy Lutomirski
2012-09-18 18:29 ` John Stultz
2012-09-19 4:50 ` Richard Cochran
2012-09-19 5:30 ` Andy Lutomirski
2012-09-19 16:31 ` John Stultz
2012-09-19 17:03 ` Richard Cochran
2012-09-19 17:54 ` John Stultz [this message]
2012-09-19 18:26 ` Andy Lutomirski
2012-09-19 20:50 ` Luck, Tony
2012-09-19 21:11 ` John Stultz
2012-09-20 7:36 ` Richard Cochran
2012-09-19 21:15 ` Andy Lutomirski
2012-09-20 14:31 ` Steven Rostedt
2012-09-20 17:32 ` Andy Lutomirski
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